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pulmonaryPFTfunc Tests.pdf
- 2. What exactly are PFTs? â«The term encompasses a wide variety of objective methods to assess lung function. (the primary function is gas exchange). â«Examples include: â«Spirometry â«Lung volumes by helium dilution or body plethysmography â«Blood gases â«Exercise tests â«Diffusing capacity â«Bronchial challenge testing â«Pulse oximetry
- 3. ADVANTAGES OF PFT - â«Add to diagnosis of disease (pulmonary and cardiac). â«May help guide management of a disease process. â«Can help monitor progression of disease and effectiveness of treatment. â«Aids in pre-operative assessment of patients.
- 4. INDICATIONS- â«Diagnostic â«To evaluate symptoms, signs, or abnormal laboratory tests â«Symptoms: dyspnea, wheezing, orthopnea, cough, phlegm production, â«chest pain â«Signs: diminished breath sounds, overinflation, expiratory slowing, â«cyanosis, chest deformity, unexplained crackles â«Abnormal laboratory tests: hypoxemia, hypercapnia, polycythemia, â«abnormal chest radiographs â«To measure the effect of disease on pulmonary function â«To screen individuals at risk of having pulmonary diseases â«Smokers â«Individuals in occupations with exposures to injurious substances â«Some routine physical examinations â«To assess preoperative risk â«To assess prognosis (lung transplant, etc.) â«To assess health status before enrollment in strenuous physical activity programs
- 5. â«Monitoring â«To assess therapeutic interventions â« -bronchodilator therapy â« -Steroid treatment for asthma, interstitial lung disease, etc. â« -Management of congestive heart failure â« -Other (antibiotics in cystic fibrosis, etc.) â«To describe the course of diseases affecting lung function â«-Pulmonary diseases â« Obstructive airways diseases â« Interstitial lung diseases â«-Cardiac diseases â« Congestive heart failure â«-Neuromuscular diseases â« Guillain-Barre Syndrome â«To monitor persons in occupations with exposure to injurious agents â«To monitor for adverse reactions to drugs with known pulmonary toxicity
- 6. INDICATIONS (contd-) â«Disability/Impairment Evaluations â« To assess patients as part of a rehabilitation program â« -Medical â« -Industrial â« -Vocational â«To assess risks as part of an insurance evaluation â«Public Health â« Epidemiologic surveys â« -Comparison of health status of populations living in different â« environments â« -Validation of subjective complaints in occupational/environmental â« settings â«Derivation of reference equations (From ATS, 1994)
- 7. Spirometry â«âSpirometry is a medical test that measures the volume of air an individual inhales or exhales as a function of time. (ATS, 1994)â
- 8. Brief History â«John Hutchinson (1811-1861)âinventor of the spirometer and originator of the term vital capacity (VC). â«Original spirometer consisted of a calibrated bell turned upside down in water. â«Observed that VC was directly related to height and inversely related to age. â«Observations based on living and deceased subjects.
- 9. Silhouette of Hutchinson Performing Spirometry
- 10. Lung Volumes and Capacities
- 11. Lung Volumes â«Tidal Volume (TV): volume of air inhaled or exhaled with each breath during quiet breathing â«Inspiratory Reserve Volume (IRV): maximum volume of air inhaled from the end- inspiratory tidal position â«Expiratory Reserve Volume (ERV): maximum volume of air that can be exhaled from resting end-expiratory tidal position
- 12. Lung Volumes â«Residual Volume (RV): â«Volume of air remaining in lungs after maximium exhalation â«Indirectly measured (FRC-ERV) not by spirometry
- 13. Lung Capacities â«Total Lung Capacity (TLC): Sum of all volume compartments or volume of air in lungs after maximum inspiration â«Vital Capacity (VC): TLC minus RV or maximum volume of air exhaled from maximal inspiratory level â«Inspiratory Capacity (IC): Sum of IRV and TV or the maximum volume of air that can be inhaled from the end-expiratory tidal position
- 14. Lung Capacities (cont.) â«Functional Residual Capacity (FRC): â«Sum of RV and ERV or the volume of air in the lungs at end-expiratory tidal position â«Measured with multiple- breath closed-circuit helium dilution, multiple-breath open-circuit nitrogen washout, or body plethysmography (not by spirometry)
- 15. What information does a spirometer yield? â«A spirometer can be used to measure the following: â«FVC and its derivatives (such as FEV1, FEF 25-75%) â«Forced inspiratory vital capacity (FIVC) â«Peak expiratory flow rate â«Maximum voluntary ventilation (MVV) â«Slow VC â«IC, IRV, and ERV â«Pre and post bronchodilator studies
- 16. Lung Factors Affecting Spirometry â«Mechanical properties â«Resistive elements
- 17. Mechanical Properties â«Compliance â«Describes the stiffness of the lungs â«Change in volume over the change in pressure â«Elastic recoil â«The tendency of the lung to return to itâs resting state â«A lung that is fully stretched has more elastic recoil and thus larger maximal flows
- 18. Resistive Properties â«Determined by airway caliber â«Affected by â«Lung volume â«Bronchial smooth muscles â«Airway collapsibility
- 19. Factors That Affect Lung Volumes â«Age â«Sex â«Height â«Weight â«Race â«Disease
- 20. Technique â«Have patient seated comfortably â«Closed-circuit technique â«Place nose clip on â«Have patient breathe on mouthpiece â«Have patient take a deep breath as fast as possible â«Blow out as hard as they can until you tell them to stop
- 22. Terminology â«Forced vital capacity (FVC): â«Total volume of air that can be exhaled forcefully from TLC â«The majority of FVC can be exhaled in <3 seconds in normal people, but often is much more prolonged in obstructive diseases â«Measured in liters (L)
- 23. FVC â«Interpretation of % predicted: â«> 80% Normal â«70-79% Mild reduction â«50%-69% Moderate reduction â«<50% Severe reduction FVC
- 24. Terminology â«Forced expiratory volume in 1 second: (FEV1) â«Volume of air forcefully expired from full inflation (TLC) in the first second â«Measured in liters (L) â«Normal people can exhale more than 75-80% of their FVC in the first second; thus the FEV1/FVC can be utilized to characterize lung disease
- 25. FEV1 â«Interpretation of % predicted: â«>80% Normal â«60%-80% Mild obstruction â«40-60% Moderate obstruction â«<40% Severe obstruction FEV1 FVC
- 26. CLINICAL RANGE FOR FEV1 â«CLINICAL RANGE PATIENT GROUP 3 to 4.5L normal adult 1.5 to 2.5L mild to moderate obstruction <1L handicaped 0.8 disability 0.5 severe emphysema
- 27. FVC AND FEV1 IN DISEASED STATE â«DISEASED STATE FVC FEV1 FEV1/FVC â«Airway obstruction normal decreased decreased Asthma, bronchitis â«Stiff lung Pneumonia,pulmonary decreased decreased normal Oedema, pulmonary Fibrosis â«Respiratory muscle decreased decreased normal Weakness MG, myopathies
- 28. Terminology â«Forced expiratory flow 25- 75% (FEF25-75) â«Mean forced expiratory flow during middle half of FVC â«Measured in L/sec â«May reflect effort independent expiration and the status of the small airways â«Highly variable â«Depends heavily on FVC
- 29. FEF25-75 â«Interpretation of % predicted: â«>79% Normal â«60-79% Mild obstruction â«40-59% Moderate obstruction â«<40% Severe obstruction
- 30. PEAK EXPIRATORY FLOW RATE â«It is the maximum flow generated in the first fraction of second during a forced expiratory manoeuvre â«The major contribution to the peak flow is from large central airways â«Peak flows is useful for monitoring than diagnosing airflow obstruction
- 31. MAXIMUM VOLUNTARY VENTILATION â«Is the largest volume of gas that can be breathed in one minute by voluntary effort for 10 to 15 seconds and the results are extraplotted to 1 minute â«Healthy adults â 170l/min â«Is decreased in obstructive lung disease â«A poor performance suggests that patient may have pulmonary problems postoperatively due to muscle weakness
- 32. Acceptability Criteria â«Good start of test â«No coughing â«No variable flow â«No early termination â«Reproducibility
- 33. PHYSIOLOGICAL DETERMINANTS OF MAXIMUM FLOW RATE â«Degree of effort of driving pressure generated by muscle contraction â«Elastic recoil pressure of lung â«Airway resistance
- 34. DEGREE OF EFFORT â«The expiratory effort is maximum at high lung volumes near TLC and decreases as the lung vulume decreases â«Whereas the inspiratory effort is maximum at low lung volume near RV and diminishes at higher lung volume
- 35. ELASTIC RECOIL PRESSURE OF LUNG â«At all lung volumes from RV to TLC the lung has tendancy to recoil inward â«The lung pressure is greatest at TLC(25 to 30 cm of H2O) and lowest at RV â«The PL is opposed by outward recoil pressure of chest wall(PCW) â«The recoil pressure of the respiratory system is algebric sum of PL + PCW â«PL and PCW are equal and opposite at some point, ie FRC and it is respiratory normal resting volume
- 36. â«Is determined by size of airways â«Because airways are largest at high lung volumes and smallest at RV ,so airway resistance is greatest at RV and least at TLC AIRWAY RESISTANCE
- 37. AIRWAY RESISTANCE Relationship between lung volume and airways resistance. Total lung capacity is at right; residual volume is at left. Solid line = normal lung; dashed line = abnormal (emphysematous) lung. R V FR C TLC
- 38. EQUAL PRESSURE POINT CONCEPTOF EXPIRATORY FLOW LIMITATIONS Schematic diagram illustrating dynamic compression of airways and the equal pressure point hypothesis during a forced expiration. Left: Passive (eupneic) expiration. Intrapleural pressure is â8 cm H2O, alveolar elastic recoil pressure is +10 cm H2O, and alveolar pressure is +2 cm H2O. Right: Forced expiration at the same lung volume. Intrapleural pressure is +25 cm H2O, alveolar elastic recoil pressure is +10 cm H2O, and alveolar pressure is +35 cm H2O.
- 39. Flow-Volume Loop â«Illustrates maximum expiratory and inspiratory flow- volume curves â«Useful to help characterize disease states (e.g. obstructive vs. restrictive) Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003
- 41. Obstructive Disorders â«Characterized by a limitation of expiratory airflow â«Examples: asthma, COPD â«Decreased: FEV1, FEF25- 75, FEV1/FVC ratio (<0.8) â«Increased or Normal: TLC
- 42. Spirometry in Obstructive Disease â«Slow rise in upstroke â«May not reach plateau
- 43. Restrictive Lung Disease â«Characterized by diminished lung volume due to: â«change in alteration in lung parenchyma (interstitial lung disease) â«disease of pleura, chest wall (e.g. scoliosis), or neuromuscular apparatus (e.g. muscular dystrophy) â«Decreased TLC, FVC â«Normal or increased: FEV1/FVC ratio
- 44. Restrictive Disease â«Rapid upstroke as in normal spirometry â«Plateau volume is low
- 45. Large Airway Obstruction â«Characterized by a truncated inspiratory or expiratory loop
- 46. FLOW-VOLUME LOOPS IN DIFFERENT TYPES OF AIRWAY OBSTRUCTION Inspiratory and expiratory flow-volume curves representing the patterns in: A: Fixed intra- or extrathoracic obstruction. B: Variable extrathoracic obstruction. C: Variable intrathoracic obstruction. TLC = total lung capacity; RV = residual volume; Paw = airway pressure; Patm = atmospheric pressure; Ppl = intrapleural pressure.
- 47. FIXED OBSTRUCTION â«As in benigin strictures resulting from trachostomy or tracheal intubation, a tumor or mass like goitre â«The air flow is limited to similar extent in both inspiration and expiration as breathing occurs through fixed external resistance â«Both inspiratory and expiratory phases on the loop show plateaus
- 48. VARIABLE EXTRATHORACIC OBSTRUCTION â«As in vocal cord paralysis, pharangeal weakness, neuromuscular disorder â«The obstruction worsens during inspiration because the negative pressure narrows the trachea and inspiratory flow is reduced to greater extent than expiratory flow
- 49. VARIABLE INTRATHORACIC OBSTRUCTION â«As occurs in tumors of trachea and major bronchi â«The obstruction is maximal during expiration because of increase intrathoracic pressure compressing airway â«The narrowing is minimal in inspiration because intrathoracic pressure is lower than airway pressure â«The flow-volume loop shows a greater decrease in the expiratory loop
- 50. Bronchodilator Test Indications: â«Establish reversibility of airway obstruction. â«Evaluation of effect of bronchodilator for patients with obstructive disease. â«Help plan long-term bronchodilator therapy.
- 51. Bronchodilator Test Avoidance before test â«Inhaled sympathomimetics 6 hours â«Short-acting oral methylxanthines 12 hours â«Long-acting oral methylxanthines 24 hours
- 52. Bronchodilator Test â«Positive bronchodilator response: Increase of FVC or FEV1 â„ 12% or Increase of FVC or FEV1 â„ 0.2 L from baseline â«Significant bronchodilator response: Increase of FVC or FEV1 12-24% â«Marked bronchodilator response: Increase of FVC or FEV1 â„ 25%
- 53. Bronchial Provocative Test Indications: 1. History of wheezing with normal pulmonary function tests 2. Chronic cough 3. Exercise tolerance 4. Unexplained dyspnea 5. Identifying specific provocative factors 6. Study the pathophysiology of acute reversible bronchospasm
- 54. Bronchial Provocative Test Avoidance before test â«Sympathomimetic drugs â„6 hours â«Methylxanthines â„12 hours â«Sustained-release methylxanthines â„48 hours â«Cromolym sodium 48 hours â«Corticosteroids 12 hours â«Significant exercise â„2 hours â«Exposure to cold air â„2 hours â«Smoking â„6 hours â«Ingestion of coffee, cola, or chocolate drinks â„6 hours
- 55. Bronchial Provocative Test% f SGAW â«Bronchial challenge with methacholine, exercise, allergic materials, SO2, cigarette smoke. â«Positive bronchoprovocative response: Decrease of FEV1 â„ 20% Decrease of PEFR â„ 20%
- 56. Distribution of Ventilation Single-breath nitrogen test: â«A full inhalation of 100% O2 form RV. â«Phase I: Air in trachea and upper airway. â«Phase II: Alveolar gas begins washing out the dead space O2. â«Phase III: Alveolar gas. â«Phase IV: Expired air from the apical region with higher percentage of N2.
- 57. Distribution of Ventilation Single-breath nitrogen test: â«Normal slope of phase III: 1.0-2.5%N2/L. â«Phase IV: The onset of airway closure in the dependent regions, called âclosing volumeâ. It expressed as a fraction of vital capacity in percent(CV/VC%), showed final 15% vital capacity in normal individual
- 60. Gas exchange in the lungs
- 62. Diffusing Capacity â«A single-breath(SB) method(SBDLCO). â«A He-CO-O2 mixed gas(0.3% CO, 10% He, 20% O2, 69.7% N2). â«A 10 seconds breath-holding, and should be a minimum of 5 seconds. â«The vital capacity should exceed 1.5 L for results to be acceptable.
- 64. Pulmonary Function Test Interpretation of gas transfer DLCO(Diffusing capacity) Severity Normal 81-140% Mild 61-80% Moderate 41-60% Severe <41%
- 65. Diffusing Capacity â«It estimates the patientâs ability to absorb alveolar gases. â«Reduced DLCO: Disorders of the pulmonary parenchyma, vascular abnormalities, reductions in effective alveolar units, and anemia. â«Elevated DLCO: Left-to-right intracardiac shunt, polycythemia, and post-exercise physiology.
- 66. Diffusing Capacity Causes of a decreased diffusing capacity
- 67. ABG â«Results: pH / PCO2 / PO2 / bicarbonate / base excess â«Usually obtained from radial, brachial, femoral, axillary, or dorsalis pedis artery â«Drawn in heparinized syringe â«Must be measured within 15 minutes or glycolysis will occur with lactic acid production, decreased pH, and increased PCO2 â«Sample can be stored on ice for 1 to 2 hours â«Heparin may significantly lower PCO2 by dilution, esp. in children when small samples taken
- 68. ABG normal values â«pH: 7.35 â 7.45 â«PCO2: 35 â 45 mmHg â«PO2: 75 â 105 mmHg â«Bicarbonate: 20 â 26 mmoles/L â«Base excess: -3 to +3 mmoles/L
- 69. pH â«Acidemia = blood pH < 7.35 â«Alkalemia = blood pH > 7.45 â«Acidosis = a process which causes acid to accumulate â«Alkalosis = a process which causes alkali accumulation â«Altered pH đĄȘ next determine if respiratory (CO2) or metabolic (HCO3 -) â«Buffers: substance that can absorb or donate H+ â«Bicarb(HCO3 -), Hb, serum proteins, phosphate(HPO4 -)
- 70. PaCO2 â«Hypercapnia â increased CO2 â«Hypocapnia â decreased CO2 â«*Rule: an increase of PCO2 by 10 mmHg causes a decrease in pH by 0.08, likewise, a decrease of PCO2 by 10 mmHg will increase pH by 0.08 â«So an acute increase in CO2 to 60 should cause a drop in pH to 7.24
- 71. Bicarbonate â«A calculated value from: [H+] = 24 * (PaCO2/[HCO3 -]) â«Values alter due to acidosis/alkalosis â«Base excess is calculated directly using PaCO2, pH, and bicarbonate values â«Rule: a decrease in bicarb. by 10 mmoles decreases the pH by 0.15, likewise, an increase in bicarb. By 10 mmoles increases pH by 0.15 â«A bicarb. of 13 would result in a pH of 7.25 â«Total body bicarb. deficit = (base deficit * wt in Kg * 0.4), in mEq/L, usually replace Âœ of deficit
- 72. Respiratory Acidosis â«Low pH & High PaCO2 â«Acute and chronic causes: â«Hypoventilation with hypercarbia â«CNS depression â trauma, drugs â«Decreased FRC â obesity â«Upper or lower airway obstruction â«COPD, asthma, pulmonary fibrosis â«After 1-2 days renal compensation occurs â«H+ excreted by kidney and HCO3 - reabsorbed into blood to partially correct pH
- 73. Respiratory Alkalosis â«High pH & Low PaCO2 â«Hyperventilation with hypocarbia â«Causes: hypoxic respiration, CNS Dz, encephalitis, anxiety, narcotic withdrawl, pregnancy, early septic shock, hypermetabolic states, artificial ventilation â«Renal compensation will occur causing increased excretion of HCO3 - and decreased secretion of H+ which partially corrects pH
- 74. LUNG FUNCTION OBSTRUCTIVE DISORDER RSTRICTIVE DISORDER FEV1 ââ â FVC ââ ââ FEV1/FVC â Normal or â FRC â â TLC â â PEFR â â MBC â ââ FEF25-75 â â AIRWAY RESISTANCE â â RV/TLC â â COMPLIANCE Dynamic â Static â
- 75. BED SIDE PFTs â«Breathing holding tests of sabrasez : vital capacity is checked â«Sniders test â«Auscultation over trachea
- 76. REFERENCES â«MILLER 6TH â«McGRAW-HILLS-POCKET GUIDE TO LUNG FUNCTION TESTS
- 77. Thank you