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Spirometry and DLCO is Part of PFT

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Pulmonary Function Test Dr. Abhishek Shukla Junior Resident II Department Of Respiratory Medicine King George Medical University
Pulmonary Function Testing • Spirometry • Static lung volumes • Diffusion capacity
SPIROMETRY  Spirometry, derived from the Latin words SPIRO (to breathe) and METER (to measure).  The spirometer was originally invented in the 1840’s by John Hutchinson an English surgeon  Spirometry represents the foundation of pulmonary function testing  Spirometry is a method of assessing lung function by measuring the total volume of air the patient can expel from the lungs after a maximal inhalation.  Physiological test to measure the ventilatory function of the lungs
REQUIREMENTS FOR SPIROMETRY • FLOW SPIROMETRES • MOUTH PIECE • NASAL CLIPS • CALIBRATION SYRINGE • FILTERS • STADIOMETERS( HEIGHT MEASURING) • WEIGHING SCALES • THERMOMETER( ROOM TEMPERATURE)
Indication s
Contraindications Increase in myocardial demand or changes in BP • Acute MI within 1 wk • ↓BP or severe HTN • Significant arrhythmia • Non-compensated heart failure • Uncontrolled PH • Acute cor pulmonale • Clinically unstable Pulmonary embolism • History of syncope related to forced expiration/cough Increased intracranial/intraocular/sinus pressure • Cerebral aneurysm • Brain surgery within 4 wk • Recent concussion with continuing symptoms • Eye surgery within 1 wk • Sinus surgery or middle ear surgery or infection within 1 wk Increased Intrathoracic or intraabdominal pressure • Presence of pneumothorax • Thoracic surgery within 4 wk • Abdominal surgery within 4 wk • Late-term pregnancy Infection Control Issues • Active or suspected transmissible infection, including TB • Conditions predisposing to transmission of infections, eg. hemoptysis, significant secretions, or oral lesions or oral bleeding Standardization of Spirometry 2019 Update An Official American Thoracic Society and European Respiratory Society Technical Statement
Activities to be Avoided before PFT Activity Reason Time Smoking/ Vaping To avoid acute bronchoconstriction due to smoke inhalation 1 hour Consuming intoxicants To avoid problems in coordination, comprehension, and physical ability 8 hours Vigorous exercise To avoid potential exercise-induced bronchoconstriction 1 hour Tight/Restrictive clothing To avoid external restrictions on lung function) Standardization of Spirometry 2019 Update An Official American Thoracic Society and European Respiratory Society Technical Statement
Lung volumes and capacities Normal respiration Forced respiration
FVC maneuver Maximal Inspiration Blast of expiration Continued complete expiration Inspiration at maximal flow back to max lung volume. Four distinct phases of the FVC maneuver Standardization of Spirometry 2019 Update An Official American Thoracic Society and European Respiratory Society Technical Statement
Spirometric Indices: what do wemeasure?
Indices measured by spirometry • FVC and FEV1 • From a maximal inspiration, • Maximal volume of air exhaled with maximally forced effort: FVC • Maximal volume exhaled in 1st second of a forced expiration: FEV1 • FEV1/FVC ratio: Ratio of FEV1 to FVC X 100 (expressed as a percent)
FEV1/FVC RATIO • This ratio is used to differentiate an obstructive from a restrictive pattern. In Obstructive disorders, FEV1 decreases more significantly ; while in Restrictive disorders, the ratio is either normal or increased • Normally, the FEV1/FVC ratio is greater than 0.7, but it decreases (to values <0.7) with normal aging . In children, however, it is higher and can reach as high as 0.9 . The decline in this ratio as we age reflects the decrease in elastic recoil of the lungs that occurs with aging.
Other Measurements: FEF 25-75% • F.E.F. 25-75%: Forced expiratory flow 25-75% • Mean forced expiratory flow between 25% and 75% of the FVC • Also called maximal mid expiratory flow rate (MMEFR) • Represents the average of all instantaneous flow rates measured from the time when 25 % of the vital capacity has been exhaled to the point when 75% vital capacity has been exhaled • Used to be considered as a measure of small airways function BUT Highly dependent on the validity of the FVC measurement and the level of expiratory effort
• Peak expiratory flow rate: • The highest flow achieved from a maximum forced expiratory manoeuvre started without hesitation from a position of maximal inspiration  Normally, it takes place immediately after the start of the exhalation and it is effort-dependent.  PEF drops with a submaximal effort in obstructive and, to a lesser extent, restrictive disorders. PEF measured in the laboratory is similar to the peak expiratory flow rate (in liters/minute) Other Measurements: PEFR, PIFR PEFR • Peak inspiratory flow rate: • Highest inspiratory flow achieved from a maximum forced inspiration, starting without hesitation from the point of maximal lung deflation, expressed in L*s-1 PIFR
Other Flows and Volumes • FIF50: Flow at 50% inhaled vital capacity • The ratio of FEF at 50% VC to forced inspiratory flow at 50% VC (FEF50/FIF50) is sometimes used as an indicator of upper airway obstruction • SVC: Slow vital capacity also called the Vital Capacity (VC) is similar to the FVC, but the exhalation is intentionally slow. In a normal subject, the SVC is equivalent to the FVC while in patients with an obstructive lung disorder, the SVC is usually larger than the FVC. • Timed VCs -FEV6 – Forced expiratory volume in six seconds: FEV6 is defined as the volume of air exhaled in the first 6 seconds of the FVC and its only significance is that it can sometimes substitute for the FVC in patients who fail to exhale completely or to be substituted for FVC for “office” spirometry
• The spirometer is calibrated every morning to ensure that it records accurate values. Technique of spirometry • The technician instructs him/her to inhale maximally to TLC, then exhale as fast and as completely as possible to record the FVC. • The point at which no more air can be exhaled is the RV. • The patient is then instructed to inhale fully to TLC again in order to record the IVC
P SPIROMETRY – POSSIBLE SIDE EFFECT - Possible Side Effects Feeling light-headed Headache Facial redness Fainting: reduced venous return or vasovagal attack (reflex) Transient urinary incontinence
Spirometry - Usual Patterns • Normal Pattern • Obstructive Pattern • Restrictive Pattern • Mixed Pattern
NORMAL SPIROGRAM The ideal VT curve should either have a plateau for 1 s or show an effort of at least 6 s
NORMAL FLOW-VOLUME CURVE
NORMAL FLOW-VOLUME CURVE IT TELLS MORE…… (1) TLC is represented by the leftmost end of the curve (cannot be measured by spirometry); (2) RV is represented by the rightmost end of the curve (cannot be measured by spirometry); (3) FVC is represented by the width of the curve; (4) PEF is represented by the height of the curve; (5) FEV1 is the distance from TLC to the 1st second mark (normally located at ~ 80% of the FVC )
MAXIMAL FLOW VOLUME LOOP The expiratory curve forming the upper and having a peak (maximum flow = PEFR) Ascending limb – effort dependent Desending limb – effort independent the inspiratory curve is saddle shaped forming the lower parts of that loop Curve starts at residual volume And ends at TLC
Acceptability of test syncope) • Inspiration and expiration give the same VC Unacceptable Maneuvers • Hesitating start (BEV> 150ml or 5% of VC) • Submaximal blast • Coughing • Early Termination • Leak around the mouthpiece • Obstruction by tongue ATS/ERS TASK FORCE: STANDARDISATION OF LUNG FUNCTION TESTING 2005 Acceptable maneuver • Satisfactory start-of-test (SOT) without hesitation • Back extrapolation value (BEV): <5% of FVC or 150ml whichever is greater 100ml • Quick rise and sharp peak reached almost immediately • A “smooth” Flow-Volume curve • Satisfactory end-of-test (EOT): • exhalation 6s smooth continuous exhalation (3-4 s in children < EOFE >15s 10 years) and/or • a plateau (change < 25 ml) atleast 1 s • When the subject cannot or should not exhale (signs of distress, Within repeatability tolerance or greater than largest prior FVC
Back-extrapolated volume (BEV). Time 0 is found by drawing a line with a slope equal to peak flow through the point of peak flow (red line) on the volume–time curve and setting Time 0 to thepoint where this line intersects the time axis. The BEV is equal to the volume of gas exhaled beforeTime 0 (inset), which, in these two examples from the same patient, is 0.136 L for the left panel(acceptable) and 0.248 L for the right panel (unacceptable). For this patient, the BEV limit is 5%FVC=0.225 L .
Repeatabilit y Criteria Required for Usability Required for acceptability Required for both FEV₁ and FVC acceptability and usability Acceptability, Usability, and Repeatability Criteria 1. BEV ≤5% of FVC or 100mL 2. No e/o faulty zero setting 3. No glottis closure in 1st second of expiration 1. No cough in 1st second 2. No e/o obstructed mouthpiece 3. No e/o leak 4. FIVC-FVC ≤ 100ml or 5% No cough in 1st second FEV₁ 1. No glottis closure after 1st second (also) 2. Must achieve 1 of 3 EOFE criteria a. Plateau (≤25ml in last s) b. Exp time ≥15s c. Within repeatability tolerance or greater than largest prior FVC) 3. No cough in 1st second 4. No e/o obstructed mouthpiece 5. No e/o leak 6. FIVC-FVC ≤ 100ml or 5% Nothing extra FVC The difference b/w the two largest FVC values must be ≤ 150 mL The difference b/w the two largest FEV₁ values ≤ 150 mL Standardization of Spirometry 2019 Update An Official American Thoracic Society and European Respiratory Society Technical Statement
Errors Cough in 1st second Cough after 1st second Not acceptable Acceptable
Errors Glottic closure Leak Standardization of Spirometry 2019 Update An Official American Thoracic Society and European Respiratory Society Technical Statement • Sudden drop in flow in the F-V graph • Flat line in Vol-time graph
Errors • FIVC >FVC , the subject did not reach total lung capacity before blowing out. • If the inspiratory volume > FVC by more than 0.100 L or 5% of FVC (whichever is greater), maneuver not acceptable
Errors Tongue obstructing mouthpiece Submaximal effort • Rounded flow-volume curve • Less steep slope at the start of the V-T curve. • Rise time >150 ms
Errors Early termination Extra breath
REPRODUCIBLE SPIROMETRY • Three accepted tests should be obtained. • The two largest FVC should be within 150 ML and 5% difference. • The two largest FEV1 should be within 150 ML and 5% difference. • If above not possible, continue to repeat effort until 8 attempts performed or patient cannot continue, then save the best three maneuvers.
Is Test Reproducible ? Reproducible Test
Non-Reproducible Test
Ventilatory impairments
Ventilatory impairments on spirometry Ventilatory impairment Obstructive FEV₁/FVC: <LLN FVC: >LLN FEV₁: <LLN Restrictive FEV₁/FVC: >LLN FVC: <LLN FEV₁: <LLN Mixed FEV₁/FVC: <LLN FVC: <LLN FEV₁: <LLN Possible restriction Possible mixed
Interpretation
ABnORMAL SPIROGRAM
ABNORMAL FLOW – VOLUME PATTERNSATTERNS
Obstructive disorders (FV curve) : There are five features that make the diagnosis of a significant airway obstruction definite, based on this curve alone. 1 – Decreased PEF when compared to the predicted curve. 2 – Scooping of the curve after PEF, indicating airflow limitation. 3 – The 1st second mark is almost in the middle of the curve indicating that the FEV1 and FEV 1/FVC ratio are significantly decreased. 4 – FVC is decreased when compared to the predicted curve. 5 – The inspiratory component of the curve is normal, excluding a central airway obstruction
Sequence of assessment `Step 5: Assess lung volumes, if required Step 1: Check flow volume loop and volume time curve Step 2: Check FEV1/FVC Ratio (to assess presence of obstruction) Step 3: Check FVC (to assess for possible restriction) Step 3: Check FEV₁ to assess severity of ventilatory defect Step 4: Assess bronchodilator response, if done
2005 Algorithm • Use of VC (i.e., the largest VC of the SVC and FVC) in place of FVC in the ratio (i.e., FEV1/VC) (2005 ATS/ERS document) But 2021 • Using VC more sensitive but not as specific compared to FEV1/FVC • So FVC to be used for the FEV1/FVC ratio as they both should come from forced expiratory manoeuvres • Robust reference equations for the FEV1/FVC ratio but not for FEV1/VC. ATS/ERS task force: standardisation of lung function testing. 2005 ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J 2021
Obstructive defect FEV₁/FVC < LLN Different from GOLD cut off of 0.7 for COPD FEV₁/FVC: <LLN FVC: > LLN FEV₁: < LLN
Diseases Associated WITH AIRFLOW OBSTRUCTION Airflow Obstruction COPD(Chronic bronchitis and emphysema) Asthma Bronchiectasis Cystic Fibrosis Post-tuberculosis Lung cancer (greater risk in COPD) Obliterative Bronchiolitis
Severity assessment ATS/ERS 2005 Recommendations ATS/ERS 2021 Recommendations Previous FEV1 severity grading: • >70%: mild • 60 – 69%: moderate • 50 – 59%: Moderate-to-severe • 35 – 49%: severe • <35%: very severe Previous DLCO severity grading: • >60%: mild • 40 – 60%: moderate • <40% severe For all measures use z score: • -1.65 to -2.5: mild • -2.51 to -4.0: moderate • <-4.0: severe -1.65 to -2.5 -2.5 to -4 <-4 Severe Mild Z - Score Moderate ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J 2021
Bronchodilator Responsiveness • Determination of the degree of improvement of airflow in response to bronchodilator administration • Measured by changes in FEV1 and FVC Drug to avoid Time SABA 4-6 hrs SAMA 12 hrs LABA 24 hrs uLABA 36 hrs LAMA 36-48 hrs Alternate bronchodilator: ipratropium bromide 160mcg MDI, wait time 30min MDI Jet nebulizer 1. Bronchodilator Salbutamol MDI Salbutamol 2. Bronchodilator dose 400 µg delivered as 4 MDI actuations of 100 µg 5mg 3. Method of bronchodilator administration Separate MDI actuations delivered at ~30 s intervals via a holding chamber Nebulization for 10 min, driving gas air at 6-10L/min 4. Wait time prior to post bronchodilator maneuvers 15 minutes after administration of the final MDI actuation 15 minutes after completion of the administration of the nebulized dose
• the absolute and relatives change in FEV1 and FVC • inversely proportional to baseline lung function, and are associated with height, age and sex in both health and disease ATS/ERS 2005 Recommendations ATS/ERS 2021 Recommendations ⩾12% and 200 mL in FEV1 or FVC from baseline >10% of predicted value in FEV1 or FVC Change in recommendations minimizes sex and height difference in assessing BDR
Bronchodilator response FVC change : (2.37-2.1)/3.89 x 100 = 6.9%
Restrictive ventilatory defect Pre-Bronchodilator (BD) Test Obs. Pred. % Pred. FVC (L) 1.57 4.46 35 FEV1 (L) 1.28 3.39 38 FEV1/FVC (%) 82 76 FRC 1.73 3.80 45 RV (L) 1.12 2.59 43 TLC (L) 2.70 6.45 42 RV/TLC (%) 41 42 98 DLCO corr 5.06 31.64 16 FEV₁/FVC: > LLN FVC: < LLN FEV₁: < LLN
Diseases Associated with a Restrictive Defect PULMONARY Fibrosing lung diseases Pneumoconiosis Pulmonary edema Parenchymal lung tumors Lobectomy or pneumonectomy EXTRAPULMONARY Thoracic cage deformity Obesity Pregnancy Neuromuscular disorders
FV curve features of different forms of restriction: (a)The PEF can be normal or high because of the increased elastic recoil that increases the initial flow of exhaled air (b)The width of the curve (FVC) is decreased and the 1st second mark (FEV1) on the descending limb of the curve is close to the residual volume indicating a normal or high FEV 1/FVC ratio. (c) The slope of the descending limb of the curve is steeper than usual due to high lung recoil or elastance (i.e., low MMEF). The reduction in MMEF, in this case, does not indicate airflow obstruction and is related to the reduced volumes. ILD FV curve features of different forms of restriction:
Chest wall restriction (including musculoskeletal disorders, diaphragmatic distention, and obesity) (a) PEF is decreased as the elastic recoil of the lung is not increased here. (b) The slope of the curve is parallel to the predicted curve, making the whole curve looking like the predicted curve but smaller. The MMEF is similarly decreased.
NMD (or poor effort study) e.g. muscular dystrophy, amyotrophic lateral sclerosis (ALS), old poliomyelitis, paralyzed diaphragm etc. (a) The PEF is low and not sharp (the curve is convex in shape). (b) The MMEF is low
Mixed defect on spirometry FEV₁/FVC: <LLN FVC: < LLN FEV₁: < LLN
UUPPER AIRWAY OBSTRUCTION Upper Airway Obstruction The morphology of the flow–volume curve is very useful in identifying upper airway disorders. There are three types of upper airway obstruction recognizable in the FV curve .
CAUSES OF UPPER AIRWAY OBSTRUCTIONAirway Obstruction 1. Variable extrathoracic lesions (lesions above the sternal notch) -Dynamic tumors of hypopharynx or upper trachea -Vocal cord paralysis -Dynamic subglottic stenosis -External compression of upper trachea (e.g., by goiter) 2. Variable intrathoracic lesions (lesions below the sternal notch) -Dynamic tumors of the lower trachea -Tracheomalacia -Dynamic tracheal strictures -Chronic inflammatory disorders of the upper airways (e.g., Wegener granulomatosis, relapsing polychondritis) -External compression of lower trachea (e.g., by retrosternal goiter) 3. Fixed lesions (lesions at any level in the major airways) -Non-dynamic tumors at any level of upper airways -Fibrotic stricture of upper airways
DIFFUSION CAPACITY OF LUNG FOR CARBON MONOXIDE (DLCO) The DLCO measures the ability of the lungs to transfer gas from inhaled air to the red blood cells in pulmonary capillaries • Diffusing capacity is intended to provide an estimate of the rate at which test molecules move by diffusion from alveolar gas to pulmonary capillary blood flow. What's so special about CO? • CO is diffusion limited gas while oxygen is perfusion limited gas • Has a high Haldane constant • Binds with Hb 200-300 time more avidly than Oxygen • Reverse reaction being extremely slow. • Practically no back pressure/tension
Alveolar Capillary Membrane The respiratory membrane forms the diffusing barrier. It separates air within the alveoli from blood flowing in the pulmonary capillaries. It consists of the following layers: 1. Alveolar epithelium 2. Alveolar basement membrane 3. Interstitium 4. Capillary basement membrane 5. Capillary endothelium
According to Fick's equation for the diffusion of gas Vg=[k*(A)(ΔP)] / T V = volume of gas transferred per unit time K = diffusion coefficient of the gas A = surface area for gas exchange ΔP = partial pressure difference of gas T = membrane thickness Diffusion of gas across the alveolar membrane increases with: • Increased surface area of the membrane (A) • Increased alveolar pressure gradient(ΔP) • Increased solubility of the gas • Decreased membrane thickness (T)
PHYSIOLOGY
PROCEDURES DLCO is measured using the following techniques • Single breath method (Most commonly used) • Intrabreath method • Rebreathing technique(used in research purpose) • Steady state method The test gas contains: 0.3% CO 10 % tracer gas (10% helium, 0.3% methane, or 0.5 % neon) 21% oxygen Balance nitrogen
sSTEPS 1.A few cycles of tidal breathing 2. Subject exhales to RV 3. Inhales a mixture of predetermined tracer gas and CO upto vital capacity 4 . Patient is asked to hold breath for 10 seconds at TLC during which • CO mixes with RV • CO reaches alveolar membrane and diffuses across it • CO crosses RBC membrane • Binds with Hemoglobin 7. Subject exhales to RV 8. Exhaled sample is analyzed
Rapid inhalation time < 4 seconds Initial portion of expirate(approx. 750 ml) containing dead space gas is discarded and remainder is collected for analysis Normal value of DLCO – 20-30 ml co /min /mmHg In DLCO four parameter are estimated • Alveolar CO concentration at the beginning • Alveolar CO end of breath holding • Duration of breath holding • Alveolar volume during the procedure
INDICATIONS OF DLCO • OBSTRUCTIVE DISEASE • DIFFERENTIATING CHRONIC BRONCHITIS FROM EMPHYSEMA – SMOKERS WITH AIRWAY OBSTRUCTION BUT NORMAL DLCO USUALLY HAVE CHRONIC BRONCHITIS • DIFFERENTIATING ASTHMA FROM COPD – ASTHAMATICS HAVE NORMAL OR HIGH DLCO VALUES • RESTRICTIVE DISEASE • A LOW DLCO WITH REDUCED LUNG VOLUME SUGGEST ILD • EXTRAPULMONARY CAUSE OF RESTRICTION HAS NORMAL DLCO WITH REDUCED LUNG VOLUMES • PULMONARY VASCULAR DISEASES HAVE REDUCED DLCO • PRIOR TO LUNG CANCER SURGERY - A LOW DLCO INCREASE THE RISK OF POST OP MORBIDITY AND MORTALITY • DISABILITY EVALUATION A DLCO BELOW 30 PRECENT PREDICTED (<9ML/MIN/MMHG) MAY QUALIFY TOTAL DISABILITY
CONTRAINDICATIONS CHEST PAIN ABDOMINAL PAIN ORAL AND FACIAL PAIN DEMENTIA ACUTE CORONARY SYNDROME /MYOCARDIAL INFARCTION PNEUMOTHORAX HEMOPTYSIS THORACIC SURGERY ABDOMINAL SURGERY
TERMINOLOGIESin • DLCO: Diffusing capacity of the lungs for carbon monoxide • VA: The alveolar volume (VA) can be considered the number of contributing alveolar units measured by tracer gas (helium). • KCO: The carbon monoxide transfer coefficient is often written as DLCO/VA. Which indicate the efficiency of C0 transfer by alveoli Severity and classification of DLCO reduction Normal DLCO: >75% of predicted, up to 140% Mild: 60% to LLN (lower limit of normal Moderate: 40% to 60% Severe: <40%
FACTOR AFFECTING DIFFUSION CAPACITY 1. HEMOGLOBIN CONCENTRATION 2. ALVEOLAR PARTIAL PRESSURE OF OXYGEN 3. BODY POSITION 4. EXERCISE 5. ALVEOLAR VOLUME – ALVEOLAR DISTENTION DECREASE DLCO
HEMOGLOBIN CONCENTRATION • The adjusted value estimates the DLCO if the patient were to be having normal hemoglobin • DLCO predicted for Hb = (DCLO predicted x factor) where factor = (1.7 x Hb)/(10.22 + Hb) In children under 15 yrs of age and females is: corrected Dlco = Predicted Dlco * (1.7 x Hb)/(9.38 + Hb) Where Hb is expressed in gm/dl
Carboxyhemoglobin and cigarette smoking • The carboxyhemoglobin level may be elevated in the blood if the patient was smoking just prior to the DLCO measurement. • An increase of 1 percent in COHb results in a proportionate 1 percent decrease in the measured DLCO. • Smoking cessation results in a mean DLCO increase of 2 to 4 mL/min per mmHg within a few days High altitude
High altitude and alveolar partial pressure of oxygen • If the laboratory is located at high altitude, the ambient, alveolar, and arterial oxygen concentrations are lower than at sea level. • The lower arterial oxygen concentration results in less competition for CO binding to hemoglobin, increased CO uptake and increased DLCO. • And higher measured DLCO compared to a test done at sea level. • DLCO is lowered in patients receiving supplemental oxygen during the test
Body Position And Exercise DlCO is greater in supine position than in erect position as venous return increases in supine position During exercise , cardiac output increases  reduction of transit time of RBC in pulmonary capillary  increased DLCO
Volume correction in alveolar volume • Alveolar distention causes significant decrease in DLCO due to thinning of alveolar wall • • DLCO/VA (KCO) reflects alveolar CO uptake efficiency at a given volume • • In the past, the term DLCO/VA (also known as KCO) was misinterpreted as a correction factor for low lung volume, leading to potential misinterpretation of DLCO results • •KCO is DLCO expressed per litres of alveolar volume
RELATIONSHIP BETWEEN DLCO AND KCOCO & KCO (DLCO/VA & KCO (DLCO/VA DLCO = VA * KCO VA – No Of Contributing Alveolar Units Measures By Tracer Gas KCO – CO Transfer Factor Which Indicate The Efficiency Of CO Transfer By Alveoli A Decrease In DLCO Will Be Due To A Decrease In VA KCO, Or Both. • Incomplete lung expansion – In patients who have neuromuscular disorders, kyphoscoliosis, or inadequate inspiration due to poor test performance, the KCO (DLCO/VA) is elevated. • Pneumonectomy – For patients who have undergone pneumonectomy, but do not have lung disease, the VA is decreased due to discrete loss of alveolar units. Blood flow is diverted to the remaining lung and the KCO (DLCO/VA) is usually increased. A PATIENT OF EMPHYSEMA WILL HAVE REDUCED DLCO AND REDUCED KCO DUE TO LOSS OF GAS EXCHANGING SURFACE AND ALVEOLAR CAPILLARY DAMAGE
Interpretation of DLCO ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J 2021
INTERPRETATION OF DLCO DLCO = VA * KCO VA – No Of Contributing Alveolar Units Measures By Tracer Gas KCO – CO Transfer Factor Which Indicate The Efficiency Of CO Transfer By Alveoli A Decrease In DlCO Will Be Due To A Decrease In VA KCO, Or Both. Low DLCO And Low KCO: Seen In COPD With Emphysema Due To Alveolar destruction (Usually Normal In Chronic Bronchitis With An Obstructive Pattern on PFT. Smoking Can Also Cause A Decrease In DLCO DLCO And KCO Are Also Reduced In Interstitial Lung Diseases, Pulmonary fibrosis Due To The Thickening Of The Alveolar-capillary Membrane With A restrictive Pattern On PFT. A Normal DLCO With A Restrictive Pattern On PFT Suggests Neuromuscular Or chest Wall Disorder.
In Dyspnea Cases Of Unknown Etiology, The Pattern Of Normal Spirometry With low DLCO Increases The Likelihood Of Pulmonary Vascular Disease. However.This Pattern May Also Present In Other Disorders, Eg, Mild ILD. High DLCO Is Seen In Conditions Like Obesity , Asthma, Which Are Characterized by Large Lung Volumes. KCO May Be Raised In Conditions Involving Profuse pulmonary Hemorrhage (Eg, Goodpasture Syndrome, Systemic Lupus erythematosus, Granulomatosis With Polyangiitis). This Is Due To The Uptake Of CO By Free RBCs Lining The Alveoli
• Emphysema - the DLCO is reduced by loss of gas exchanging surface due to alveolar capillary damage and the KCO is low • Interstitial lung disease (ILD) – In ILD, the DLCO is decreased by diffuse alveolar capillary damage. The KCO is often reduced. • Pulmonary vascular disease – In pulmonary hypertension, the DLCO is reduced. The VA is typically normal, and the KCO (DLCO/VA) is reduced.
Increased DLCO • Altitude • Asthma • Polycythemia • Pulmonary hemorrhage • Left-to-right intracardiac shunting • Mild left heart failure - increased pulmonary capillary blood volume • Exercise just prior to the test - increased cardiac output • Mueller maneuver • Supine position
Low DLCO with normal spirometry • Anemia - mild decrease • Pulmonary vascular disease - mild to severe decrease • increased carboxyhemoglobin level • Valsalva maneuver Low DLCO with obstruction • Bronchiolitis • Combined pulmonary fibrosis and emphysema (CPFE) • Cystic fibrosis • Emphysema • Sarcoidosis • Alpha 1 anti trypsin
Low DLCO with restriction • Interstitial lung disease • Pneumonitis Low DLCO with both restriction & obstruction • Sarcoidosis (stage II through IV) • Asbestosis • Miliary tuberculosis
Body Plethysmography
RATIONALE OF BODY PLETHYSMOGRPHY • Spirometry is considered the gold standard in lung function. It can, however, not provide information on, e.g., lung residual volume (RV) and total lung capacity (TLC), while body plethysmography allows to determine these and other characteristics, such as airway resistance and intrathoracic gas volume (ITGV). • The determination of lung function by body plethysmography starts with breathing at rest, followed by the shutter maneuver continue this with spirometric measurements. • After opening of the shutter, an expiratory reserve volume (ERV) effort and an inspiratory vital capacity effort (IVC) are performed; this allows the computation of RV and TLC
PRINCIPLES OF BODY PLETHYSMOGRAPHY APPARATUS • The volume-constant whole-body plethysmograph is a chamber resembling a glass-walled telephone box in shape and volume (about 700 TO 1000 L). • During measurement the box is closed with an airtight seal, • One pressure transducer serves to measure the pressure inside the box relative to ambient pressure, another one is placed close to the mouth for recording mouth pressure during a shutter maneuver. • Respiratory flow rate is recorded by conventional equipment, such as pneumotachograph, anemometer , all are calibarated via syringe to deliver a definite volume
Principle of measurement • The principle of measurement of the commonly used plethysmographs relies on detecting changes in box pressure in combination with either changes of mouth pressure or with flow rate under defined breathing conditions. • These signals are evaluated in order to determine static lung volumes and airflow resistance • The basic physical principle exploited by body plethysmography is the law of Boyle-Mariotte
BOYLE’S LAW • The absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remain unchanged within a closed system. • that for a fixed amount of gas in a closed compartment the relative changes in the compartment’s volume are always equal in magnitude but opposite in sign to the relative changes in pressure. • Thus one can infer relative volume changes from pressure changes and, even more, absolute volumes if the absolute volume changes are known BLAW
BOYLE’S LAW
SHIFT VOLUMEVOLUME • It Is The Change In Volume By Which The Lung Generates Positive 0r Negative Alveolar Pressure • That Is , Deviation From The Volume At Which Equillibrium Of Alveolar And Box Pressure Would Hold • Represent A Small Part Of Tidal volume During Free Breathing • Inspiration is initiated from end expiration by inspiratory muscles thoracicvolume increases. • Airflow does not start immediately → pressure gradient is required for mass movement. • Airflow lags behind the changes in lung volume due to airway resistance. • If the airway is occluded during inspiration, there is decrease in alv. Pressure but no flow → Closed compartment→ Boyle law
• During inspiration the thoracic volume excursion is slightly ahead of the equilibrating mass flow . • When thoracic & lung volume ceases to increase , alveolar and box pressure will reach equilibrium. • However as long as air is flowing, the increase in lung volume is slightly greater than volume of air that has passed through the airways into lung. • This small difference represent a lag in mass flow during a breathing cycle and is called “shift volume”
• the shift volume corresponds to a deviation of volume relative to that which the same mass of air would occupy at equilibrium pressure • Shift volume is the tiny pressure generating fraction of the tidal volume, tiny→ ~ 1/100 • Volume defect in the lung is equal in magnitude but opposite in sign to the volume defect in the box. • Volume of box = Tot box vol-Body volume (est. from weight) • Why shift volume ? – Provides the link to box pressure – Allows determination of TGV & sRaw
• Both measurements rely on the fact that the volume defect within the lung represented by the shift volume is necessarily equal in magnitude but opposite in sign to a volume defect in the body box • As the free volume of the box is known (total box volume minus body volume as estimated from body weight), Boyle Mariotte’s law is applicable and allows to derive the shift volume from the pressure change. Specifically, the relative change in the free box volume is equal but opposite in sign to the relative change in box pressure.
RV and TLC MEASUREMENT FROM FRC STEP 1 – FRC pleth Step 2 – ERV Step 3 – FRC – ERV = RV Step 4 – IC Step 5 –FRCpleth + IC = TLC
• Pm plotted on y axis, shift volume on x axis. • Inspiratory efforts causes neg Pm & positive Shift.Volume • Little deviation in both inspiratory & expiratory efforts. • Expiratory efforts causes visa- versa • The slope Pm vs shift volume ∞ to FRCpleth.
Alveolar ∆P ∞ Shift volume ∆P is obtaining the mouth pressure when it is occluded- zero flow. Pmouth= Palv  How to achieve ‘zero flow’ or occlusion maneuver ? Shutter mechanism prevents entry or exit of air to lungs, therefore normal inspiratory or expiratory efforts cause compression and decompression of the lung volume. This movement is transmitted to box as in normal flow. ∆P mo
Lung volume and shift volume • When moving a plunger a equivalent distance in a short vs. long syringe, the pressure change will be greater in the short cylinder . • Larger the lung volume for a given shift volume, the smaller the pressure change. • Greater the pressure change, the smaller lung volume. relative to shift volume. • In a large lung occlusion pressure curve will be more flat,and in a small lung more steep.
• Specific airway resistance(sRaw) • Airway resistance (Raw) • Conductance (Gaw) AIRWAY RESISTANCE BY BODY BOX PLETHYSMOGRAPHY
AIRWAY RESISTANCE It Is Flow Resistance Of Airways , That Is Ratio Of Alveolar Driving Pressure Minus Mouth Pressure To Flow Rate . It Is Calculated From sRaw And FRC It Indicates The Alveolar Pressure Needed To Generate A Reference Flow Rate Of 1 L/S
Specific airway resistance • Resistance is def. =driving pressure = • Flow sRaw= Palv – Pmo Flow rate • The more the driving pressure for a given flow, the greater the resistance. • Pmo- constant during unimpeded breathing • Palv- not available during free breathing. • Shift volume represents the thoracic excursions which is needed to establish the driving pressure to the lung. • Though not identical, closely related to driving pressure. • Ratio of shift volume to flow rate is called specific airway resistance or sRaw
• sRaw total • sRaw effective • sRaw at .5Ls-1
Total specific resistance resistance. • The sRtot is determined by a straight line between maximal inspiratory and maximal expiratory shift volume points • The outstanding characteristic of sRtot is its sensitivity to partial obstruction of peripheral airways. • The potential disadvantage of sRtot would appear to be a greater variability from test to test, as a consequence of using only two points at the extremes of inspiratory and expiratory shift volume.
• If airflow rate is plotted on the vertical axis and shift volume on the horizontal axis, closed loops are obtained. • The reciprocal slope of the breathing loop represents the sRAW. • Normally the curves are straight lines • A more flat curve indicates an elevated shift volume relative to airflow and therby an increase of sRaw. • Various respiratory diseases provide different patterns.
Normal • Normal subjects manifest a steep ,closed and linear loop during tidal breathing without hysteresis, ie no “openness” • Flattening= increased Ὠ, Openness = localised resistance ! • During tidal breathing the upper and lower extremities of the loop become slightly curvilinear- ‘s’ shape
Large airway obstruction  There is uniformly increased airway resistance and not localised, there is little hysteresis or “openness”  Obstructive loop – flat and opened  Linear sRaw loop that is tilted clockwise, manifesting a slope less steep than normal reflects increased Raw  The tangent has changed which show that airflow is taking time to go through airway
Small airway obstruction • In patients with non-homogenous airway obstruction(in term of trapped air (emphysema )), there is – “opening” / hysteresis in the loop – Alinerierity • This represents the expiratory flow limitation due to trapped air or the dynamic compression which occurs in expiration. • Open loop with shift to right • Denotes the large changes in shift volume that occurs at mid-expiration without comparable increases in flow.
Fixed localised central upper airway obstruction • Seen in fixed or functional stenosis of the airways like laryngeal abnormality or VC palsy • Flow limitation during inspiration, in that at sufficiently high flows further increases in driving pressure does not increase in airflow.
Restrictive lung diseases • Can be suspected when FVC is reduced and FEV1/FVC is normal or elevated. • However can be confirmed only by demonstration of a reduced TLC by plethysmography. • TLC below 5th percentile of normal value is considered as restrictive lung disease.
Obstructive diseases • Characterized by a normal or elevated FRC, TLC, and RV, and elevated Raw and sRaw. • Additionally determination of RV and RV%TLC allows to determine the degree of hyperinflation. • In the presence of severe defect, plethysmographic volumes tends to overestimated, as pressure changes are not properly transmitted to the mouth. Mild Moderate Severe RV/TLC >95th percentile - < 140% 140 -170 % >170 %
• Body plethysmography can also demonstrate the effects of Rx on hyperinflation – Decrease in FRC following bronchodilator Rx – Decrease following successful Rx of AE-COPD • These determination’s are not influenced by the patient effort, which may be substantially decreased in the presence of hyperinflation. • Body plethysmography directly measures the FRC.
Pseudorestriction • An increase in RV or RV/TLC above the 95th percentile may indicate hyperinflation or air trapping due to the presence of airway obstruction • Increase in RV or RV/TLC: one of the earliest manifestations of small airway disease • With progression, lung hyperinflation and air trapping are reflected by increases in FRC or FRC/TLC and often in TLC. • An increased FRC/TLC indicates a reduced inspiratory capacity (IC), which is a hallmark of COPD
Thank You

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(Spirometry + dlco+ body plethysmography).pptx

  • 1.
    Pulmonary Function Test Dr.Abhishek Shukla Junior Resident II Department Of Respiratory Medicine King George Medical University
  • 2.
    Pulmonary Function Testing •Spirometry • Static lung volumes • Diffusion capacity
  • 3.
    SPIROMETRY  Spirometry, derivedfrom the Latin words SPIRO (to breathe) and METER (to measure).  The spirometer was originally invented in the 1840’s by John Hutchinson an English surgeon  Spirometry represents the foundation of pulmonary function testing  Spirometry is a method of assessing lung function by measuring the total volume of air the patient can expel from the lungs after a maximal inhalation.  Physiological test to measure the ventilatory function of the lungs
  • 4.
    REQUIREMENTS FOR SPIROMETRY • FLOWSPIROMETRES • MOUTH PIECE • NASAL CLIPS • CALIBRATION SYRINGE • FILTERS • STADIOMETERS( HEIGHT MEASURING) • WEIGHING SCALES • THERMOMETER( ROOM TEMPERATURE)
  • 5.
  • 6.
    Contraindications Increase in myocardial demand or changes in BP • Acute MIwithin 1 wk • ↓BP or severe HTN • Significant arrhythmia • Non-compensated heart failure • Uncontrolled PH • Acute cor pulmonale • Clinically unstable Pulmonary embolism • History of syncope related to forced expiration/cough Increased intracranial/intraocular/sinus pressure • Cerebral aneurysm • Brain surgery within 4 wk • Recent concussion with continuing symptoms • Eye surgery within 1 wk • Sinus surgery or middle ear surgery or infection within 1 wk Increased Intrathoracic or intraabdominal pressure • Presence of pneumothorax • Thoracic surgery within 4 wk • Abdominal surgery within 4 wk • Late-term pregnancy Infection Control Issues • Active or suspected transmissible infection, including TB • Conditions predisposing to transmission of infections, eg. hemoptysis, significant secretions, or oral lesions or oral bleeding Standardization of Spirometry 2019 Update An Official American Thoracic Society and European Respiratory Society Technical Statement
  • 7.
    Activities to beAvoided before PFT Activity Reason Time Smoking/ Vaping To avoid acute bronchoconstriction due to smoke inhalation 1 hour Consuming intoxicants To avoid problems in coordination, comprehension, and physical ability 8 hours Vigorous exercise To avoid potential exercise-induced bronchoconstriction 1 hour Tight/Restrictive clothing To avoid external restrictions on lung function) Standardization of Spirometry 2019 Update An Official American Thoracic Society and European Respiratory Society Technical Statement
  • 8.
    Lung volumes andcapacities Normal respiration Forced respiration
  • 9.
    FVC maneuver Maximal Inspiration Blast of expiration Continued complete expiration Inspirationat maximal flow back to max lung volume. Four distinct phases of the FVC maneuver Standardization of Spirometry 2019 Update An Official American Thoracic Society and European Respiratory Society Technical Statement
  • 10.
  • 11.
    Indices measured byspirometry • FVC and FEV1 • From a maximal inspiration, • Maximal volume of air exhaled with maximally forced effort: FVC • Maximal volume exhaled in 1st second of a forced expiration: FEV1 • FEV1/FVC ratio: Ratio of FEV1 to FVC X 100 (expressed as a percent)
  • 12.
    FEV1/FVC RATIO • Thisratio is used to differentiate an obstructive from a restrictive pattern. In Obstructive disorders, FEV1 decreases more significantly ; while in Restrictive disorders, the ratio is either normal or increased • Normally, the FEV1/FVC ratio is greater than 0.7, but it decreases (to values <0.7) with normal aging . In children, however, it is higher and can reach as high as 0.9 . The decline in this ratio as we age reflects the decrease in elastic recoil of the lungs that occurs with aging.
  • 13.
    Other Measurements: FEF25-75% • F.E.F. 25-75%: Forced expiratory flow 25-75% • Mean forced expiratory flow between 25% and 75% of the FVC • Also called maximal mid expiratory flow rate (MMEFR) • Represents the average of all instantaneous flow rates measured from the time when 25 % of the vital capacity has been exhaled to the point when 75% vital capacity has been exhaled • Used to be considered as a measure of small airways function BUT Highly dependent on the validity of the FVC measurement and the level of expiratory effort
  • 14.
    • Peak expiratoryflow rate: • The highest flow achieved from a maximum forced expiratory manoeuvre started without hesitation from a position of maximal inspiration  Normally, it takes place immediately after the start of the exhalation and it is effort-dependent.  PEF drops with a submaximal effort in obstructive and, to a lesser extent, restrictive disorders. PEF measured in the laboratory is similar to the peak expiratory flow rate (in liters/minute) Other Measurements: PEFR, PIFR PEFR • Peak inspiratory flow rate: • Highest inspiratory flow achieved from a maximum forced inspiration, starting without hesitation from the point of maximal lung deflation, expressed in L*s-1 PIFR
  • 15.
    Other Flows andVolumes • FIF50: Flow at 50% inhaled vital capacity • The ratio of FEF at 50% VC to forced inspiratory flow at 50% VC (FEF50/FIF50) is sometimes used as an indicator of upper airway obstruction • SVC: Slow vital capacity also called the Vital Capacity (VC) is similar to the FVC, but the exhalation is intentionally slow. In a normal subject, the SVC is equivalent to the FVC while in patients with an obstructive lung disorder, the SVC is usually larger than the FVC. • Timed VCs -FEV6 – Forced expiratory volume in six seconds: FEV6 is defined as the volume of air exhaled in the first 6 seconds of the FVC and its only significance is that it can sometimes substitute for the FVC in patients who fail to exhale completely or to be substituted for FVC for “office” spirometry
  • 16.
    • The spirometeris calibrated every morning to ensure that it records accurate values. Technique of spirometry • The technician instructs him/her to inhale maximally to TLC, then exhale as fast and as completely as possible to record the FVC. • The point at which no more air can be exhaled is the RV. • The patient is then instructed to inhale fully to TLC again in order to record the IVC
  • 17.
    P SPIROMETRY – POSSIBLESIDE EFFECT - Possible Side Effects Feeling light-headed Headache Facial redness Fainting: reduced venous return or vasovagal attack (reflex) Transient urinary incontinence
  • 18.
    Spirometry - UsualPatterns • Normal Pattern • Obstructive Pattern • Restrictive Pattern • Mixed Pattern
  • 19.
    NORMAL SPIROGRAM The idealVT curve should either have a plateau for 1 s or show an effort of at least 6 s
  • 20.
  • 21.
    NORMAL FLOW-VOLUME CURVE ITTELLS MORE…… (1) TLC is represented by the leftmost end of the curve (cannot be measured by spirometry); (2) RV is represented by the rightmost end of the curve (cannot be measured by spirometry); (3) FVC is represented by the width of the curve; (4) PEF is represented by the height of the curve; (5) FEV1 is the distance from TLC to the 1st second mark (normally located at ~ 80% of the FVC )
  • 22.
    MAXIMAL FLOW VOLUMELOOP The expiratory curve forming the upper and having a peak (maximum flow = PEFR) Ascending limb – effort dependent Desending limb – effort independent the inspiratory curve is saddle shaped forming the lower parts of that loop Curve starts at residual volume And ends at TLC
  • 23.
    Acceptability of test syncope) •Inspiration and expiration give the same VC Unacceptable Maneuvers • Hesitating start (BEV> 150ml or 5% of VC) • Submaximal blast • Coughing • Early Termination • Leak around the mouthpiece • Obstruction by tongue ATS/ERS TASK FORCE: STANDARDISATION OF LUNG FUNCTION TESTING 2005 Acceptable maneuver • Satisfactory start-of-test (SOT) without hesitation • Back extrapolation value (BEV): <5% of FVC or 150ml whichever is greater 100ml • Quick rise and sharp peak reached almost immediately • A “smooth” Flow-Volume curve • Satisfactory end-of-test (EOT): • exhalation 6s smooth continuous exhalation (3-4 s in children < EOFE >15s 10 years) and/or • a plateau (change < 25 ml) atleast 1 s • When the subject cannot or should not exhale (signs of distress, Within repeatability tolerance or greater than largest prior FVC
  • 24.
    Back-extrapolated volume (BEV).Time 0 is found by drawing a line with a slope equal to peak flow through the point of peak flow (red line) on the volume–time curve and setting Time 0 to thepoint where this line intersects the time axis. The BEV is equal to the volume of gas exhaled beforeTime 0 (inset), which, in these two examples from the same patient, is 0.136 L for the left panel(acceptable) and 0.248 L for the right panel (unacceptable). For this patient, the BEV limit is 5%FVC=0.225 L .
  • 25.
    Repeatabilit y Criteria Required for Usability Requiredfor acceptability Required for both FEV₁ and FVC acceptability and usability Acceptability, Usability, and Repeatability Criteria 1. BEV ≤5% of FVC or 100mL 2. No e/o faulty zero setting 3. No glottis closure in 1st second of expiration 1. No cough in 1st second 2. No e/o obstructed mouthpiece 3. No e/o leak 4. FIVC-FVC ≤ 100ml or 5% No cough in 1st second FEV₁ 1. No glottis closure after 1st second (also) 2. Must achieve 1 of 3 EOFE criteria a. Plateau (≤25ml in last s) b. Exp time ≥15s c. Within repeatability tolerance or greater than largest prior FVC) 3. No cough in 1st second 4. No e/o obstructed mouthpiece 5. No e/o leak 6. FIVC-FVC ≤ 100ml or 5% Nothing extra FVC The difference b/w the two largest FVC values must be ≤ 150 mL The difference b/w the two largest FEV₁ values ≤ 150 mL Standardization of Spirometry 2019 Update An Official American Thoracic Society and European Respiratory Society Technical Statement
  • 26.
    Errors Cough in 1stsecond Cough after 1st second Not acceptable Acceptable
  • 27.
    Errors Glottic closure Leak Standardizationof Spirometry 2019 Update An Official American Thoracic Society and European Respiratory Society Technical Statement • Sudden drop in flow in the F-V graph • Flat line in Vol-time graph
  • 28.
    Errors • FIVC >FVC, the subject did not reach total lung capacity before blowing out. • If the inspiratory volume > FVC by more than 0.100 L or 5% of FVC (whichever is greater), maneuver not acceptable
  • 29.
    Errors Tongue obstructing mouthpieceSubmaximal effort • Rounded flow-volume curve • Less steep slope at the start of the V-T curve. • Rise time >150 ms
  • 30.
  • 31.
    REPRODUCIBLE SPIROMETRY • Threeaccepted tests should be obtained. • The two largest FVC should be within 150 ML and 5% difference. • The two largest FEV1 should be within 150 ML and 5% difference. • If above not possible, continue to repeat effort until 8 attempts performed or patient cannot continue, then save the best three maneuvers.
  • 32.
    Is Test Reproducible? Reproducible Test
  • 33.
  • 34.
  • 35.
    Ventilatory impairments onspirometry Ventilatory impairment Obstructive FEV₁/FVC: <LLN FVC: >LLN FEV₁: <LLN Restrictive FEV₁/FVC: >LLN FVC: <LLN FEV₁: <LLN Mixed FEV₁/FVC: <LLN FVC: <LLN FEV₁: <LLN Possible restriction Possible mixed
  • 36.
  • 37.
  • 38.
    ABNORMAL FLOW –VOLUME PATTERNSATTERNS
  • 39.
    Obstructive disorders (FVcurve) : There are five features that make the diagnosis of a significant airway obstruction definite, based on this curve alone. 1 – Decreased PEF when compared to the predicted curve. 2 – Scooping of the curve after PEF, indicating airflow limitation. 3 – The 1st second mark is almost in the middle of the curve indicating that the FEV1 and FEV 1/FVC ratio are significantly decreased. 4 – FVC is decreased when compared to the predicted curve. 5 – The inspiratory component of the curve is normal, excluding a central airway obstruction
  • 41.
    Sequence of assessment `Step5: Assess lung volumes, if required Step 1: Check flow volume loop and volume time curve Step 2: Check FEV1/FVC Ratio (to assess presence of obstruction) Step 3: Check FVC (to assess for possible restriction) Step 3: Check FEV₁ to assess severity of ventilatory defect Step 4: Assess bronchodilator response, if done
  • 42.
    2005 Algorithm • Useof VC (i.e., the largest VC of the SVC and FVC) in place of FVC in the ratio (i.e., FEV1/VC) (2005 ATS/ERS document) But 2021 • Using VC more sensitive but not as specific compared to FEV1/FVC • So FVC to be used for the FEV1/FVC ratio as they both should come from forced expiratory manoeuvres • Robust reference equations for the FEV1/FVC ratio but not for FEV1/VC. ATS/ERS task force: standardisation of lung function testing. 2005 ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J 2021
  • 43.
    Obstructive defect FEV₁/FVC <LLN Different from GOLD cut off of 0.7 for COPD FEV₁/FVC: <LLN FVC: > LLN FEV₁: < LLN
  • 44.
    Diseases Associated WITHAIRFLOW OBSTRUCTION Airflow Obstruction COPD(Chronic bronchitis and emphysema) Asthma Bronchiectasis Cystic Fibrosis Post-tuberculosis Lung cancer (greater risk in COPD) Obliterative Bronchiolitis
  • 45.
    Severity assessment ATS/ERS 2005Recommendations ATS/ERS 2021 Recommendations Previous FEV1 severity grading: • >70%: mild • 60 – 69%: moderate • 50 – 59%: Moderate-to-severe • 35 – 49%: severe • <35%: very severe Previous DLCO severity grading: • >60%: mild • 40 – 60%: moderate • <40% severe For all measures use z score: • -1.65 to -2.5: mild • -2.51 to -4.0: moderate • <-4.0: severe -1.65 to -2.5 -2.5 to -4 <-4 Severe Mild Z - Score Moderate ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J 2021
  • 46.
    Bronchodilator Responsiveness • Determinationof the degree of improvement of airflow in response to bronchodilator administration • Measured by changes in FEV1 and FVC Drug to avoid Time SABA 4-6 hrs SAMA 12 hrs LABA 24 hrs uLABA 36 hrs LAMA 36-48 hrs Alternate bronchodilator: ipratropium bromide 160mcg MDI, wait time 30min MDI Jet nebulizer 1. Bronchodilator Salbutamol MDI Salbutamol 2. Bronchodilator dose 400 µg delivered as 4 MDI actuations of 100 µg 5mg 3. Method of bronchodilator administration Separate MDI actuations delivered at ~30 s intervals via a holding chamber Nebulization for 10 min, driving gas air at 6-10L/min 4. Wait time prior to post bronchodilator maneuvers 15 minutes after administration of the final MDI actuation 15 minutes after completion of the administration of the nebulized dose
  • 47.
    • the absoluteand relatives change in FEV1 and FVC • inversely proportional to baseline lung function, and are associated with height, age and sex in both health and disease ATS/ERS 2005 Recommendations ATS/ERS 2021 Recommendations ⩾12% and 200 mL in FEV1 or FVC from baseline >10% of predicted value in FEV1 or FVC Change in recommendations minimizes sex and height difference in assessing BDR
  • 48.
    Bronchodilator response FVC change: (2.37-2.1)/3.89 x 100 = 6.9%
  • 49.
    Restrictive ventilatory defect Pre-Bronchodilator(BD) Test Obs. Pred. % Pred. FVC (L) 1.57 4.46 35 FEV1 (L) 1.28 3.39 38 FEV1/FVC (%) 82 76 FRC 1.73 3.80 45 RV (L) 1.12 2.59 43 TLC (L) 2.70 6.45 42 RV/TLC (%) 41 42 98 DLCO corr 5.06 31.64 16 FEV₁/FVC: > LLN FVC: < LLN FEV₁: < LLN
  • 50.
    Diseases Associated witha Restrictive Defect PULMONARY Fibrosing lung diseases Pneumoconiosis Pulmonary edema Parenchymal lung tumors Lobectomy or pneumonectomy EXTRAPULMONARY Thoracic cage deformity Obesity Pregnancy Neuromuscular disorders
  • 51.
    FV curve featuresof different forms of restriction: (a)The PEF can be normal or high because of the increased elastic recoil that increases the initial flow of exhaled air (b)The width of the curve (FVC) is decreased and the 1st second mark (FEV1) on the descending limb of the curve is close to the residual volume indicating a normal or high FEV 1/FVC ratio. (c) The slope of the descending limb of the curve is steeper than usual due to high lung recoil or elastance (i.e., low MMEF). The reduction in MMEF, in this case, does not indicate airflow obstruction and is related to the reduced volumes. ILD FV curve features of different forms of restriction:
  • 52.
    Chest wall restriction (includingmusculoskeletal disorders, diaphragmatic distention, and obesity) (a) PEF is decreased as the elastic recoil of the lung is not increased here. (b) The slope of the curve is parallel to the predicted curve, making the whole curve looking like the predicted curve but smaller. The MMEF is similarly decreased.
  • 53.
    NMD (or pooreffort study) e.g. muscular dystrophy, amyotrophic lateral sclerosis (ALS), old poliomyelitis, paralyzed diaphragm etc. (a) The PEF is low and not sharp (the curve is convex in shape). (b) The MMEF is low
  • 54.
    Mixed defect onspirometry FEV₁/FVC: <LLN FVC: < LLN FEV₁: < LLN
  • 55.
    UUPPER AIRWAY OBSTRUCTION UpperAirway Obstruction The morphology of the flow–volume curve is very useful in identifying upper airway disorders. There are three types of upper airway obstruction recognizable in the FV curve .
  • 56.
    CAUSES OF UPPERAIRWAY OBSTRUCTIONAirway Obstruction 1. Variable extrathoracic lesions (lesions above the sternal notch) -Dynamic tumors of hypopharynx or upper trachea -Vocal cord paralysis -Dynamic subglottic stenosis -External compression of upper trachea (e.g., by goiter) 2. Variable intrathoracic lesions (lesions below the sternal notch) -Dynamic tumors of the lower trachea -Tracheomalacia -Dynamic tracheal strictures -Chronic inflammatory disorders of the upper airways (e.g., Wegener granulomatosis, relapsing polychondritis) -External compression of lower trachea (e.g., by retrosternal goiter) 3. Fixed lesions (lesions at any level in the major airways) -Non-dynamic tumors at any level of upper airways -Fibrotic stricture of upper airways
  • 59.
    DIFFUSION CAPACITY OFLUNG FOR CARBON MONOXIDE (DLCO) The DLCO measures the ability of the lungs to transfer gas from inhaled air to the red blood cells in pulmonary capillaries • Diffusing capacity is intended to provide an estimate of the rate at which test molecules move by diffusion from alveolar gas to pulmonary capillary blood flow. What's so special about CO? • CO is diffusion limited gas while oxygen is perfusion limited gas • Has a high Haldane constant • Binds with Hb 200-300 time more avidly than Oxygen • Reverse reaction being extremely slow. • Practically no back pressure/tension
  • 61.
    Alveolar Capillary Membrane Therespiratory membrane forms the diffusing barrier. It separates air within the alveoli from blood flowing in the pulmonary capillaries. It consists of the following layers: 1. Alveolar epithelium 2. Alveolar basement membrane 3. Interstitium 4. Capillary basement membrane 5. Capillary endothelium
  • 62.
    According to Fick'sequation for the diffusion of gas Vg=[k*(A)(ΔP)] / T V = volume of gas transferred per unit time K = diffusion coefficient of the gas A = surface area for gas exchange ΔP = partial pressure difference of gas T = membrane thickness Diffusion of gas across the alveolar membrane increases with: • Increased surface area of the membrane (A) • Increased alveolar pressure gradient(ΔP) • Increased solubility of the gas • Decreased membrane thickness (T)
  • 63.
  • 65.
    PROCEDURES DLCO is measuredusing the following techniques • Single breath method (Most commonly used) • Intrabreath method • Rebreathing technique(used in research purpose) • Steady state method The test gas contains: 0.3% CO 10 % tracer gas (10% helium, 0.3% methane, or 0.5 % neon) 21% oxygen Balance nitrogen
  • 67.
    sSTEPS 1.A few cyclesof tidal breathing 2. Subject exhales to RV 3. Inhales a mixture of predetermined tracer gas and CO upto vital capacity 4 . Patient is asked to hold breath for 10 seconds at TLC during which • CO mixes with RV • CO reaches alveolar membrane and diffuses across it • CO crosses RBC membrane • Binds with Hemoglobin 7. Subject exhales to RV 8. Exhaled sample is analyzed
  • 68.
    Rapid inhalation time< 4 seconds Initial portion of expirate(approx. 750 ml) containing dead space gas is discarded and remainder is collected for analysis Normal value of DLCO – 20-30 ml co /min /mmHg In DLCO four parameter are estimated • Alveolar CO concentration at the beginning • Alveolar CO end of breath holding • Duration of breath holding • Alveolar volume during the procedure
  • 72.
    INDICATIONS OF DLCO •OBSTRUCTIVE DISEASE • DIFFERENTIATING CHRONIC BRONCHITIS FROM EMPHYSEMA – SMOKERS WITH AIRWAY OBSTRUCTION BUT NORMAL DLCO USUALLY HAVE CHRONIC BRONCHITIS • DIFFERENTIATING ASTHMA FROM COPD – ASTHAMATICS HAVE NORMAL OR HIGH DLCO VALUES • RESTRICTIVE DISEASE • A LOW DLCO WITH REDUCED LUNG VOLUME SUGGEST ILD • EXTRAPULMONARY CAUSE OF RESTRICTION HAS NORMAL DLCO WITH REDUCED LUNG VOLUMES • PULMONARY VASCULAR DISEASES HAVE REDUCED DLCO • PRIOR TO LUNG CANCER SURGERY - A LOW DLCO INCREASE THE RISK OF POST OP MORBIDITY AND MORTALITY • DISABILITY EVALUATION A DLCO BELOW 30 PRECENT PREDICTED (<9ML/MIN/MMHG) MAY QUALIFY TOTAL DISABILITY
  • 73.
    CONTRAINDICATIONS CHEST PAIN ABDOMINAL PAIN ORALAND FACIAL PAIN DEMENTIA ACUTE CORONARY SYNDROME /MYOCARDIAL INFARCTION PNEUMOTHORAX HEMOPTYSIS THORACIC SURGERY ABDOMINAL SURGERY
  • 74.
    TERMINOLOGIESin • DLCO: Diffusingcapacity of the lungs for carbon monoxide • VA: The alveolar volume (VA) can be considered the number of contributing alveolar units measured by tracer gas (helium). • KCO: The carbon monoxide transfer coefficient is often written as DLCO/VA. Which indicate the efficiency of C0 transfer by alveoli Severity and classification of DLCO reduction Normal DLCO: >75% of predicted, up to 140% Mild: 60% to LLN (lower limit of normal Moderate: 40% to 60% Severe: <40%
  • 75.
    FACTOR AFFECTING DIFFUSIONCAPACITY 1. HEMOGLOBIN CONCENTRATION 2. ALVEOLAR PARTIAL PRESSURE OF OXYGEN 3. BODY POSITION 4. EXERCISE 5. ALVEOLAR VOLUME – ALVEOLAR DISTENTION DECREASE DLCO
  • 77.
    HEMOGLOBIN CONCENTRATION • Theadjusted value estimates the DLCO if the patient were to be having normal hemoglobin • DLCO predicted for Hb = (DCLO predicted x factor) where factor = (1.7 x Hb)/(10.22 + Hb) In children under 15 yrs of age and females is: corrected Dlco = Predicted Dlco * (1.7 x Hb)/(9.38 + Hb) Where Hb is expressed in gm/dl
  • 78.
    Carboxyhemoglobin and cigarettesmoking • The carboxyhemoglobin level may be elevated in the blood if the patient was smoking just prior to the DLCO measurement. • An increase of 1 percent in COHb results in a proportionate 1 percent decrease in the measured DLCO. • Smoking cessation results in a mean DLCO increase of 2 to 4 mL/min per mmHg within a few days High altitude
  • 79.
    High altitude andalveolar partial pressure of oxygen • If the laboratory is located at high altitude, the ambient, alveolar, and arterial oxygen concentrations are lower than at sea level. • The lower arterial oxygen concentration results in less competition for CO binding to hemoglobin, increased CO uptake and increased DLCO. • And higher measured DLCO compared to a test done at sea level. • DLCO is lowered in patients receiving supplemental oxygen during the test
  • 80.
    Body Position AndExercise DlCO is greater in supine position than in erect position as venous return increases in supine position During exercise , cardiac output increases  reduction of transit time of RBC in pulmonary capillary  increased DLCO
  • 81.
    Volume correction inalveolar volume • Alveolar distention causes significant decrease in DLCO due to thinning of alveolar wall • • DLCO/VA (KCO) reflects alveolar CO uptake efficiency at a given volume • • In the past, the term DLCO/VA (also known as KCO) was misinterpreted as a correction factor for low lung volume, leading to potential misinterpretation of DLCO results • •KCO is DLCO expressed per litres of alveolar volume
  • 82.
    RELATIONSHIP BETWEEN DLCOAND KCOCO & KCO (DLCO/VA & KCO (DLCO/VA DLCO = VA * KCO VA – No Of Contributing Alveolar Units Measures By Tracer Gas KCO – CO Transfer Factor Which Indicate The Efficiency Of CO Transfer By Alveoli A Decrease In DLCO Will Be Due To A Decrease In VA KCO, Or Both. • Incomplete lung expansion – In patients who have neuromuscular disorders, kyphoscoliosis, or inadequate inspiration due to poor test performance, the KCO (DLCO/VA) is elevated. • Pneumonectomy – For patients who have undergone pneumonectomy, but do not have lung disease, the VA is decreased due to discrete loss of alveolar units. Blood flow is diverted to the remaining lung and the KCO (DLCO/VA) is usually increased. A PATIENT OF EMPHYSEMA WILL HAVE REDUCED DLCO AND REDUCED KCO DUE TO LOSS OF GAS EXCHANGING SURFACE AND ALVEOLAR CAPILLARY DAMAGE
  • 85.
    Interpretation of DLCO ERS/ATStechnical standard on interpretive strategies for routine lung function tests. Eur Respir J 2021
  • 86.
    INTERPRETATION OF DLCO DLCO= VA * KCO VA – No Of Contributing Alveolar Units Measures By Tracer Gas KCO – CO Transfer Factor Which Indicate The Efficiency Of CO Transfer By Alveoli A Decrease In DlCO Will Be Due To A Decrease In VA KCO, Or Both. Low DLCO And Low KCO: Seen In COPD With Emphysema Due To Alveolar destruction (Usually Normal In Chronic Bronchitis With An Obstructive Pattern on PFT. Smoking Can Also Cause A Decrease In DLCO DLCO And KCO Are Also Reduced In Interstitial Lung Diseases, Pulmonary fibrosis Due To The Thickening Of The Alveolar-capillary Membrane With A restrictive Pattern On PFT. A Normal DLCO With A Restrictive Pattern On PFT Suggests Neuromuscular Or chest Wall Disorder.
  • 87.
    In Dyspnea CasesOf Unknown Etiology, The Pattern Of Normal Spirometry With low DLCO Increases The Likelihood Of Pulmonary Vascular Disease. However.This Pattern May Also Present In Other Disorders, Eg, Mild ILD. High DLCO Is Seen In Conditions Like Obesity , Asthma, Which Are Characterized by Large Lung Volumes. KCO May Be Raised In Conditions Involving Profuse pulmonary Hemorrhage (Eg, Goodpasture Syndrome, Systemic Lupus erythematosus, Granulomatosis With Polyangiitis). This Is Due To The Uptake Of CO By Free RBCs Lining The Alveoli
  • 88.
    • Emphysema -the DLCO is reduced by loss of gas exchanging surface due to alveolar capillary damage and the KCO is low • Interstitial lung disease (ILD) – In ILD, the DLCO is decreased by diffuse alveolar capillary damage. The KCO is often reduced. • Pulmonary vascular disease – In pulmonary hypertension, the DLCO is reduced. The VA is typically normal, and the KCO (DLCO/VA) is reduced.
  • 89.
    Increased DLCO • Altitude •Asthma • Polycythemia • Pulmonary hemorrhage • Left-to-right intracardiac shunting • Mild left heart failure - increased pulmonary capillary blood volume • Exercise just prior to the test - increased cardiac output • Mueller maneuver • Supine position
  • 90.
    Low DLCO withnormal spirometry • Anemia - mild decrease • Pulmonary vascular disease - mild to severe decrease • increased carboxyhemoglobin level • Valsalva maneuver Low DLCO with obstruction • Bronchiolitis • Combined pulmonary fibrosis and emphysema (CPFE) • Cystic fibrosis • Emphysema • Sarcoidosis • Alpha 1 anti trypsin
  • 91.
    Low DLCO withrestriction • Interstitial lung disease • Pneumonitis Low DLCO with both restriction & obstruction • Sarcoidosis (stage II through IV) • Asbestosis • Miliary tuberculosis
  • 92.
  • 94.
    RATIONALE OF BODYPLETHYSMOGRPHY • Spirometry is considered the gold standard in lung function. It can, however, not provide information on, e.g., lung residual volume (RV) and total lung capacity (TLC), while body plethysmography allows to determine these and other characteristics, such as airway resistance and intrathoracic gas volume (ITGV). • The determination of lung function by body plethysmography starts with breathing at rest, followed by the shutter maneuver continue this with spirometric measurements. • After opening of the shutter, an expiratory reserve volume (ERV) effort and an inspiratory vital capacity effort (IVC) are performed; this allows the computation of RV and TLC
  • 95.
    PRINCIPLES OF BODY PLETHYSMOGRAPHY APPARATUS •The volume-constant whole-body plethysmograph is a chamber resembling a glass-walled telephone box in shape and volume (about 700 TO 1000 L). • During measurement the box is closed with an airtight seal, • One pressure transducer serves to measure the pressure inside the box relative to ambient pressure, another one is placed close to the mouth for recording mouth pressure during a shutter maneuver. • Respiratory flow rate is recorded by conventional equipment, such as pneumotachograph, anemometer , all are calibarated via syringe to deliver a definite volume
  • 100.
    Principle of measurement •The principle of measurement of the commonly used plethysmographs relies on detecting changes in box pressure in combination with either changes of mouth pressure or with flow rate under defined breathing conditions. • These signals are evaluated in order to determine static lung volumes and airflow resistance • The basic physical principle exploited by body plethysmography is the law of Boyle-Mariotte
  • 101.
    BOYLE’S LAW • Theabsolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remain unchanged within a closed system. • that for a fixed amount of gas in a closed compartment the relative changes in the compartment’s volume are always equal in magnitude but opposite in sign to the relative changes in pressure. • Thus one can infer relative volume changes from pressure changes and, even more, absolute volumes if the absolute volume changes are known BLAW
  • 102.
  • 106.
    SHIFT VOLUMEVOLUME • ItIs The Change In Volume By Which The Lung Generates Positive 0r Negative Alveolar Pressure • That Is , Deviation From The Volume At Which Equillibrium Of Alveolar And Box Pressure Would Hold • Represent A Small Part Of Tidal volume During Free Breathing • Inspiration is initiated from end expiration by inspiratory muscles thoracicvolume increases. • Airflow does not start immediately → pressure gradient is required for mass movement. • Airflow lags behind the changes in lung volume due to airway resistance. • If the airway is occluded during inspiration, there is decrease in alv. Pressure but no flow → Closed compartment→ Boyle law
  • 107.
    • During inspirationthe thoracic volume excursion is slightly ahead of the equilibrating mass flow . • When thoracic & lung volume ceases to increase , alveolar and box pressure will reach equilibrium. • However as long as air is flowing, the increase in lung volume is slightly greater than volume of air that has passed through the airways into lung. • This small difference represent a lag in mass flow during a breathing cycle and is called “shift volume”
  • 108.
    • the shiftvolume corresponds to a deviation of volume relative to that which the same mass of air would occupy at equilibrium pressure • Shift volume is the tiny pressure generating fraction of the tidal volume, tiny→ ~ 1/100 • Volume defect in the lung is equal in magnitude but opposite in sign to the volume defect in the box. • Volume of box = Tot box vol-Body volume (est. from weight) • Why shift volume ? – Provides the link to box pressure – Allows determination of TGV & sRaw
  • 109.
    • Both measurementsrely on the fact that the volume defect within the lung represented by the shift volume is necessarily equal in magnitude but opposite in sign to a volume defect in the body box • As the free volume of the box is known (total box volume minus body volume as estimated from body weight), Boyle Mariotte’s law is applicable and allows to derive the shift volume from the pressure change. Specifically, the relative change in the free box volume is equal but opposite in sign to the relative change in box pressure.
  • 112.
    RV and TLCMEASUREMENT FROM FRC STEP 1 – FRC pleth Step 2 – ERV Step 3 – FRC – ERV = RV Step 4 – IC Step 5 –FRCpleth + IC = TLC
  • 114.
    • Pm plottedon y axis, shift volume on x axis. • Inspiratory efforts causes neg Pm & positive Shift.Volume • Little deviation in both inspiratory & expiratory efforts. • Expiratory efforts causes visa- versa • The slope Pm vs shift volume ∞ to FRCpleth.
  • 115.
    Alveolar ∆P ∞Shift volume ∆P is obtaining the mouth pressure when it is occluded- zero flow. Pmouth= Palv  How to achieve ‘zero flow’ or occlusion maneuver ? Shutter mechanism prevents entry or exit of air to lungs, therefore normal inspiratory or expiratory efforts cause compression and decompression of the lung volume. This movement is transmitted to box as in normal flow. ∆P mo
  • 116.
    Lung volume andshift volume • When moving a plunger a equivalent distance in a short vs. long syringe, the pressure change will be greater in the short cylinder . • Larger the lung volume for a given shift volume, the smaller the pressure change. • Greater the pressure change, the smaller lung volume. relative to shift volume. • In a large lung occlusion pressure curve will be more flat,and in a small lung more steep.
  • 117.
    • Specific airwayresistance(sRaw) • Airway resistance (Raw) • Conductance (Gaw) AIRWAY RESISTANCE BY BODY BOX PLETHYSMOGRAPHY
  • 120.
    AIRWAY RESISTANCE It IsFlow Resistance Of Airways , That Is Ratio Of Alveolar Driving Pressure Minus Mouth Pressure To Flow Rate . It Is Calculated From sRaw And FRC It Indicates The Alveolar Pressure Needed To Generate A Reference Flow Rate Of 1 L/S
  • 121.
    Specific airway resistance •Resistance is def. =driving pressure = • Flow sRaw= Palv – Pmo Flow rate • The more the driving pressure for a given flow, the greater the resistance. • Pmo- constant during unimpeded breathing • Palv- not available during free breathing. • Shift volume represents the thoracic excursions which is needed to establish the driving pressure to the lung. • Though not identical, closely related to driving pressure. • Ratio of shift volume to flow rate is called specific airway resistance or sRaw
  • 122.
    • sRaw total • sRaweffective • sRaw at .5Ls-1
  • 123.
    Total specific resistance resistance. •The sRtot is determined by a straight line between maximal inspiratory and maximal expiratory shift volume points • The outstanding characteristic of sRtot is its sensitivity to partial obstruction of peripheral airways. • The potential disadvantage of sRtot would appear to be a greater variability from test to test, as a consequence of using only two points at the extremes of inspiratory and expiratory shift volume.
  • 124.
    • If airflowrate is plotted on the vertical axis and shift volume on the horizontal axis, closed loops are obtained. • The reciprocal slope of the breathing loop represents the sRAW. • Normally the curves are straight lines • A more flat curve indicates an elevated shift volume relative to airflow and therby an increase of sRaw. • Various respiratory diseases provide different patterns.
  • 125.
    Normal • Normal subjectsmanifest a steep ,closed and linear loop during tidal breathing without hysteresis, ie no “openness” • Flattening= increased Ὠ, Openness = localised resistance ! • During tidal breathing the upper and lower extremities of the loop become slightly curvilinear- ‘s’ shape
  • 126.
    Large airway obstruction There is uniformly increased airway resistance and not localised, there is little hysteresis or “openness”  Obstructive loop – flat and opened  Linear sRaw loop that is tilted clockwise, manifesting a slope less steep than normal reflects increased Raw  The tangent has changed which show that airflow is taking time to go through airway
  • 127.
    Small airway obstruction •In patients with non-homogenous airway obstruction(in term of trapped air (emphysema )), there is – “opening” / hysteresis in the loop – Alinerierity • This represents the expiratory flow limitation due to trapped air or the dynamic compression which occurs in expiration. • Open loop with shift to right • Denotes the large changes in shift volume that occurs at mid-expiration without comparable increases in flow.
  • 128.
    Fixed localised centralupper airway obstruction • Seen in fixed or functional stenosis of the airways like laryngeal abnormality or VC palsy • Flow limitation during inspiration, in that at sufficiently high flows further increases in driving pressure does not increase in airflow.
  • 129.
    Restrictive lung diseases •Can be suspected when FVC is reduced and FEV1/FVC is normal or elevated. • However can be confirmed only by demonstration of a reduced TLC by plethysmography. • TLC below 5th percentile of normal value is considered as restrictive lung disease.
  • 130.
    Obstructive diseases • Characterizedby a normal or elevated FRC, TLC, and RV, and elevated Raw and sRaw. • Additionally determination of RV and RV%TLC allows to determine the degree of hyperinflation. • In the presence of severe defect, plethysmographic volumes tends to overestimated, as pressure changes are not properly transmitted to the mouth. Mild Moderate Severe RV/TLC >95th percentile - < 140% 140 -170 % >170 %
  • 131.
    • Body plethysmographycan also demonstrate the effects of Rx on hyperinflation – Decrease in FRC following bronchodilator Rx – Decrease following successful Rx of AE-COPD • These determination’s are not influenced by the patient effort, which may be substantially decreased in the presence of hyperinflation. • Body plethysmography directly measures the FRC.
  • 139.
    Pseudorestriction • An increasein RV or RV/TLC above the 95th percentile may indicate hyperinflation or air trapping due to the presence of airway obstruction • Increase in RV or RV/TLC: one of the earliest manifestations of small airway disease • With progression, lung hyperinflation and air trapping are reflected by increases in FRC or FRC/TLC and often in TLC. • An increased FRC/TLC indicates a reduced inspiratory capacity (IC), which is a hallmark of COPD
  • 141.

Editor's Notes

  • #3 Other pft-body plethysmography ,nitrogen washout method for static vol. Methacoline cha test. Single breath Dlco tech
  • #14 The Maximum Mid-Expiratory Flow (MMEF) or FEF25–75, however, is the average flow during the middle half of the FVC (25–75% of FVC).These variables still represent the effort-independent part of the FVC.
  • #16 The reason for this is that, in obstructive lung disorders,the airways tend to collapse and close prematurely because ofthe increased positive intra-thoracic pressure during a forcefulexpiration (dynamic compression). This leads to air trapping. Accordingly, a significantly higher SVC compared to FVC suggests air-trapping
  • #17 The patient must be clinically stable, should sit upright, head erect, nose clip in place and holding the mouth-piece tightly between the lips.
  • #46 HOW MANY SD A SUBJECT IS DEVIATED FROM ITS REFERENCE VALUE
  • #111 Lung volume at which shutter is closed . At the end of normal expiration
  • #140 ELEVATED RV DUE TO PROMINENT AIR TRAPPING WITH A NORMAL OR SLIGHTLY INCREASED TLC , THERBY REDUCING THE FVC