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14. pulmonary-function-tests

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  • 1. PULMONARY FUNCTION TEST
  • 2. Lung Volumes and Capacities PFT tracings have:  Four Lung volumes: tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume  Five capacities:, inspiratory capacity, expiratory capacity, vital capacity, functional residual capacity, and total lung capacity Addition of 2 or more volumes comprise a capacity.
  • 3. Lung Volumes • Tidal Volume (TV): volume of air inhaled or exhaled with each breath during quiet breathing (6- 8 ml/kg) • Inspiratory Reserve Volume (IRV): maximum volume of air inhaled from the end-inspiratory tidal position.(1900-3300ml) • Expiratory Reserve Volume (ERV): maximum volume of air that can be exhaled from resting end-expiratory tidal position.( 700-1000ml).
  • 4. Lung Volumes • Residual Volume (RV): – Volume of air remaining in lungs after maximium exhalation (20-25 ml/kg) (1700-2100ml) – Indirectly measured (FRC-ERV) – It can not be measured by spirometry
  • 5. Lung Capacities • Total Lung Capacity (TLC): Sum of all volume compartments or volume of air in lungs after maximum inspiration (4-6 L) • Vital Capacity (VC): TLC minus RV or maximum volume of air exhaled from maximal inspiratory level. (60-70 ml/kg) (3100-4800ml) • Inspiratory Capacity (IC): Sum of IRV and TV or the maximum volume of air that can be inhaled from the end-expiratory tidal position. (2400-3800ml). • Expiratory Capacity (EC): TV+ ERV
  • 6. Lung Capacities (cont.) • Functional Residual Capacity (FRC): – Sum of RV and ERV or the volume of air in the lungs at end-expiratory tidal position.(30-35 ml/kg) (2300- 3300ml). – Measured with multiple- breath closed-circuit helium dilution, multiple-breath open-circuit nitrogen washout, or body plethysmography. – It can not be measured by spirometry)
  • 7. VOLUMES, CAPACITIES AND THEIR CLINICAL SIGNIFICANCE 1) TIDAL VOLUME (TV):  VOLUME OF AIR INHALED/EXHALED IN EACH BREATH DURING QUIET RESPIRATION.  N – 6-8 ml/kg.  TV FALLS WITH DECREASE IN COMPLIANCE, DECREASED VENTILATORY MUSCLE STRENGTH. 2) INSPIRATORY RESERVE VOLUME (IRV):  MAX. VOL. OF AIR WHICH CAN BE INSPIRED AFTER A NORMAL TIDAL INSPIRATION i.e. FROM END INSPIRATION PT.  N- 1900 ml- 3300 ml.
  • 8. CONTINUED……… 3) EXPIRATORY RESERVE VOLUME (ERV):  MAX. VOLUME OF AIR WHICH CAN BE EXPIRED AFTER A NORMAL TIDAL EXPIRATION i.e. FROM END EXPIRATION PT.  N- 700 ml – 1000 ml 4) INSPIRATORY CAPACITY (IC) :  MAX. VOL. OF AIR WHICH CAN BE INSPIRED AFTER A NORMAL TIDAL EXPIRATION.  IC = IRV + TV  N-2400 ml – 3800 ml.
  • 9. CONTINUED……….. 4) VITAL CAPACITY: COINED BY JOHN HUTCHINSON. MAX. VOL. OF AIR EXPIRED AFTER A MAX. INSPIRATION . MEASURED WITH VITALOGRAPH VC= TV+ERV+IRV N- 3.1-4.8L. OR 60-70 ml/kg VC IS COSIDERED ABNORMAL IF ≤ 80% OF PREDICTED VALUE
  • 10. FACTORS INFLUENCING VC • PHYSIOLOGICAL :  physical dimensions- directly proportional to ht.  SEX – more in males : large chest size, more muscle power, more BSA.  AGE – decreases with increasing age  STRENGTH OF RESPIRATORY MUSCLES  POSTURE – decreases in supine position  PREGNANCY- unchanged or increases by 10% ( increase in AP diameter In pregnancy)
  • 11. CONTINUED……… • PATHOLOGICAL:  DISEASE OF RESPIRATORY MUSCLES ABDOMINAL CONDITION : pain, dis.
  • 12. FACTORS DECREASING VITAL CAPACITY 1) Alteration in muscle power- d/t drugs, n-m dis., cerebral tumours. 2) Pulmonary diseases – pneumonia, chronic bronchitis, asthma, fibrosis, emphysema, pulmonary edema,. 3) Space occupying lesions in chest- tumours, pleural/pericardial effusion, kyphoscoliosis 4) Abdominal tumours, ascites.
  • 13. 5) Depression of respiration : opioids 6) Abdominal splinting – abdominal binders, tight bandages, hip spica. 7)Abdominal pain – decreases by 50% & 75% in lower & upper abdominal Surgeries respectively. 8) Posture – by altering pulmonary Blood volume.
  • 14. CONTINUED……. 6) TOTAL LUNG CAPACITY : Maximum volume of air attained in lungs after maximal inspiration. N- 4-6 l or 80-100 ml/kg TLC= VC + RV 7) RESIDUAL VOLUME (RV): Volume of air remaining in the lungs after maximal expiration. N- 1570 – 2100 ml OR 20 – 25 ml/kg.
  • 15. CONTINUED…… 8) FUNCTIONAL RESIDUAL CAPACITY (FRC):  Volume of air remaining in the lungs after normal tidal expiration, when there is no airflow. N- 2.3 -3.3 L OR 30-35 ml/kg. FRC = RV + ERV  Decreses under anaesthesia • with spontaneous Respiration – decreases by 20% • With paralysis – decreases by 16%
  • 16. FACTORS AFFECTING FRC • FRC INCREASES WITH • Increased height • Erect position (30% more than in supine) • Decreased lung recoil (e.g. emphysema) • FRC DECREASES WITH • Obesity • Muscle paralysis (especially in supine) • Supine position • Restrictive lung disease (e.g. fibrosis, Pregnancy) • Anaesthesia • FRC does NOT change with age.
  • 17. FUNCTIONS OF FRC • Oxygen store • Buffer for maintaining a steady arterial po2 • Partial inflation helps prevent atelectasis • Minimise the work of breathing • Minimise pulmonary vascular resistance • Minimised v/q mismatch • Keep airway resistance low
  • 18. Pulmonary Function Tests • The term encompasses a wide variety of objective tests to assess lung function • Provide objective and standardized measurements for assessing the presence and severity of respiratory dysfunction.
  • 19. GOALS  To predict the presence of pulmonary dysfunction To know the functional nature of disease (obstructive or restrictive. ) To assess the severity of disease To assess the progression of disease To assess the response to treatment To identify patients at increased risk of morbidity and mortality, undergoing pulmonary resection.
  • 20.  To wean patient from ventilator in icu. Medicolegal- to assess lung impairment as a result of occupational hazard. Epidemiological surveys- to assess the hazards to document incidence of disease To identify patients at perioperative risk of pulmonary complications GOALS, CONTINUED……..
  • 21. BED SIDE PFT 1) Sabrasez breath holding test: • Ask the patient to take a full but not too deep breath & hold it as long as possible. >25 SEC.-NORMAL Cardiopulmonary Reserve (CPR) 15-25 SEC- LIMITED CPR <15 SEC- VERY POOR CPR (Contraindication for elective surgery) 25- 30 SEC - 3500 ml VC 20 – 25 SEC - 3000 ml VC 15 - 20 SEC - 2500 ml VC 10 - 15 SEC - 2000 ml VC 5 - 10 SEC - 1500 ml VC
  • 22. BED SIDE PFT 2) Single breath count: After deep breath, hold it and start counting till the next breath.  N- 30-40 COUNT  Indicates vital capacity
  • 23. BED SIDE PFT 3) SCHNEIDER’S MATCH BLOWING TEST: MEASURES Maximum Breathing Capacity. Ask to blow a match stick from a distance of 6” (15 cms) with-  Mouth wide open  Chin rested/supported  No purse lipping  No head movement  No air movement in the room  Mouth and match at the same level
  • 24. BED SIDE PFT • Can not blow out a match – MBC < 60 L/min – FEV1 < 1.6L • Able to blow out a match – MBC > 60 L/min – FEV1 > 1.6L • MODIFIED MATCH TEST: DISTANCE MBC 9” >150 L/MIN. 6” >60 L/MIN. 3” > 40 L/MIN.
  • 25. BED SIDE TEST 4) COUGH TEST: DEEP BREATH F/BY COUGH  ABILITY TO COUGH  STRENGTH  EFFECTIVENESS INADEQUATE COUGH IF: FVC<20 ML/KG FEV1 < 15 ML/KG PEFR < 200 L/MIN. VC ~ 3 TIMES TV FOR EFFECTIVE COUGH. A wet productive cough / self propagated paraoxysms of coughing – patient susceptible for pulmonary Complication.
  • 26. BED SIDE TEST 5) FORCED EXPIRATORY TIME: After deep breath, exhale maximally and forcefully & keep stethoscope over trachea & listen. N FET – 3-5 SECS. OBS.LUNG DIS. - > 6 SEC RES. LUNG DIS.- < 3 SEC
  • 27. BED SIDE PFT 6) WRIGHT PEAK FLOW METER: Measures PEFR (Peak Expiratory Flow Rate) N – MALES- 450-700 L/MIN. FEMALES- 350-500 L/MIN. <200 L/ MIN. – INADEQUATE COUGH EFFICIENCY. 7) DEBONO WHISTLE BLOWING TEST: MEASURES PEFR. Patient blows down a wide bore tube at the end of which is a whistle, on the side is a hole with adjustable knob. As subject blows → whistle blows, leak hole is gradually increased till the intensity of whistle disappears. At the last position at which the whistle can be blown , the PEFR can be read off the scale.
  • 28. MEASUREMENT OF TV & MV 8)Wright respirometer : measures tv, mv • Simple and rapid • Instrument- compact, light and portable. • Disadvantage: It under- reads at low flow rates and over- reads at high flow rates. • Can be connected to endotracheal tube or face mask • Prior explanation to patients needed. • Ideally done in sitting pos. • MV- instrument record for 1 min. And read directly • TV-calculated and dividing MV by counting Respiratory Rate. • USES: 1)BED SIDE PFT • 2) ICU – WEANIG PTS. FROM Ventilation.
  • 29. DEBONO’S WHISTLE
  • 30. BED SIDE PFT 9) MICROSPIROMETERS – MEASURE VC. 10) BED SIDE PULSE OXIMETRY 11) ABG.
  • 31. CATEGORIZATION OF PFT 1) MECHANICAL VENTILATORY FUNCTIONS OF LUNG / CHEST WALL: A) STATIC LUNG VOLUMES & CAPACITIES – VC, IC, IRV, ERV, RV, FRC. B) DYNAMIC LUNG VOLUMES –FVC, FEV1, FEF 25-75%, PEFR, MVV, RESP. MUSCLE STRENGTH C) VENTILATION TESTS – TV, MV, RR.
  • 32. CATEGORIZATION OF PFT 2) GAS- EXCHANGE TESTS: A) Alveolar-arterial po2 gradient B) Diffusion capacity C) Gas distribution tests- single breath N2 test. - Multiple Breath N2 test - Helium dilution method. - Radio Xe scinitigram. D) ventilation – perfusion tests A) ABG B) single breath CO2 elimination test C) Shunt equation
  • 33. CATEGORIZATION OF PFT 3) CARDIOPULMONARY INTERACTION: A) Qualitative tests: - History , examination - Abg - Stair climbing test B) Quantitative tests - 6 min. Walk test (gold standard) www.anaesthesia.co.in
  • 34. STATIC LUNG VOLUMES AND CAPACITIES • SPIROMETRY : CORNERSTONE OF ALL PFTs. • John hutchinson – invented spirometer. • “Spirometry is a medical test that measures the volume of air an individual inhales or exhales as a function of time.” • Measures VC, FVC, FEV1, PEFR. • CAN’T MEASURE – FRC, RV, TLC.
  • 35. PREREQUISITIES • Prior explanation to the patient • Not to smoke /inhale bronchodilators 6 hrs prior or oral bronchodilators 12hrs prior. • Remove any tight clothings/ waist belt/ dentures • Pt. Seated comfortably If obese, child < 12 yrs- standing
  • 36. PREREQUISITES • Nose clip to close nostrils. • Exp. Effort shld last ≥ 4 secs. • Should not be interfered by coughing, glottic closure, mechanical obstruction. • 3 acceptable tracings taken & largest value is used.
  • 37. SPIROMETER • Double walled cylinder with water to maintain water tight seal • Inverted bell attached to pulley which carries a counterweight and pen – moves up and down as volume of bell changes • BREATHING ASSEMBLY i.E. Unidirectional breathing valves with mouth piece.
  • 38. Flow-Volume Curves and Spirograms • Two ways to record results of FVC maneuver: – Flow-volume curve---flow meter measures flow rate in L/s upon exhalation; flow plotted as function of volume – Classic spirogram---volume as a function of time
  • 39. Normal Flow-Volume Curve and Spirogram www.anaesthesia.co.in
  • 40. Spirometry Interpretation: So what constitutes normal? • Normal values vary and depend on: – Height – Age – Gender – Ethnicity
  • 41. Acceptable and Unacceptable Spirograms (from ATS, 1994) www.anaesthesia.co.in
  • 42. Measurements Obtained from the FVC Curve • FEV1---the volume exhaled during the first second of the FVC maneuver • FEF 25-75%---the mean expiratory flow during the middle half of the FVC maneuver; reflects flow through the small (<2 mm in diameter) airways • FEV1/FVC---the ratio of FEV1 to FVC X 100 (expressed as a percent); an important value because a reduction of this ratio from expected values is specific for obstructive rather than restrictive diseases
  • 43. Spirometry Interpretation: Obstructive vs. Restrictive Defect • Obstructive Disorders – Characterized by a limitation of expiratory airflow so that airways cannot empty as rapidly compared to normal (such as through narrowed airways from bronchospasm, inflammation, etc.) Examples: – Asthma – Emphysema – Cystic Fibrosis • Restrictive Disorders – Characterized by reduced lung volumes/decreased lung compliance Examples: – Interstitial Fibrosis – Scoliosis – Obesity – Lung Resection – Neuromuscular diseases – Cystic Fibrosis
  • 44. Normal vs. Obstructive vs. Restrictive (Hyatt, 2003)
  • 45. Spirometry Interpretation: Obstructive vs. Restrictive Defect • Obstructive Disorders – FVC nl or↓ – FEV1 ↓ – FEF25-75% ↓ – FEV1/FVC ↓ – TLC nl or ↑ • Restrictive Disorders – FVC ↓ – FEV1 ↓ – FEF 25-75% nl to ↓ – FEV1/FVC nl to ↑ – TLC ↓
  • 46. Spirometry Interpretation: What do the numbers mean? • FVC • Interpretation of % predicted: – 80-120% Normal – 70-79% Mild reduction – 50%-69% Moderate reduction – <50% Severe reduction FEV1 Interpretation of % predicted: – >75% Normal – 60%-75% Mild obstruction – 50-59% Moderate obstruction – <49% Severe obstruction
  • 47. Spirometry Interpretation: What do the numbers mean? • FEF 25-75% • Interpretation of % predicted: – >79% Normal – 60-79% Mild obstruction – 40-59% Moderate obstruction – <40% Severe obstruction • FEV1/FVC • Interpretation of absolute value: – 80 or higher Normal – 79 or lower Abnormal
  • 48. What about lung volumes and obstructive and restrictive disease?
  • 49. MEASUREMENTS OF VOLUMES • TLC, RV, FRC – MEASURED USING Nitrogen washout method Inert gas (helium) dilution method Total body plethysmography
  • 50. CONTINUED……….. 1) HELIUM DILUTION METHOD: Patient breathes in and out of a spirometer filled with 10% helium and 90% o2, till conc. In spirometer and lung becomes same (equilibirium). As no helium is lost; (as it is insoluble in blood) C1 X V1 = C2 ( V1 + V2) V2 = V1 ( C1 – C2) C2 V1= VOL. OF SPIROMETER V2= FRC C1= Conc.of He in the spirometer before equilibrium C2 = Conc, of He in the spirometer after equilibrium
  • 51. CONTINUED……… 2) TOTAL BODY PLETHYSMOGRAPHY: Subject sits in an air tight box. At the end of normal exhalation – shuttle of mouthpiece closed and pt. is asked to make resp. efforts. As subject inhales – expands gas volume in the lung so lung vol. increases and box pressure rises and box vol. decreases. BOYLE’S LAW: PV = CONSTANT (at constant temp.) For Box – p1v1 = p2 (v1- ∆v) For Subject – p3 x v2 =p4 (v2 - ∆v) P1- initial box pr. P2- final box pr. V1- initial box vol. ∆ v- change in box vol. P3- initial mouth pr., p4- final mouth pr. V2- FRC
  • 52. CONTINUED……… DIFFERENCE BETWEEN THE TWO METHODS: • In healthy people there is very little difference. • Gas dilution technique measures only the communicating gas volume. • Thus, • Gas trapped behind closed airways • Gas in pneumothorax • => are not measured by gas dilution technique, but measured by body plethysmograph
  • 53. CONTINUED……… 3) N2 WASH OUT METHOD: • Following a maximal expiration (RV) or normal expiration (FRC), Pt. inspires 100% O2 and then expires it into spirometer ( free of N2) → over next few minutes (usually 6-7 min.), till all the N2 is washed out of the lungs. N2 conc. of spirometer is calculated followed by total vol.of AIR exhaled. As air has 80% N2 → so actual FRC/RV is calculated.
  • 54. MEASUREMENT OF DYNAMIC LUNG VOLUMES • TIMED EXPIRED SPIROGRAMS FEF25–75% = forced expiratory flow during expiration of 25 to 75% of the FVC; FEV1 = forced expiratory volume in the first second of forced vital capacity maneuver; FVC = forced vital capacity (the maximum amount of air forcibly expired after maximum inspiration).
  • 55. FORCED VITAL CAPACITY (FVC) Max vol. Of air which can be expired out as forcefully and rapidly as possible, following a maximal inspiration to TLC.  Exhaled volume is recorded with respect to time.  Indirectly reflects flow resistance property of airways.  Normal healthy subjects have VC = FVC.  Prior instruction to patients, practice attempts as it needs patient cooperation and effect.  Exhalation should take at least 4 sec and should not be interrupted by cough, glottic closure or mechanical obstruction.
  • 56. FORCED VITAL CAPACITY IN 1 SEC. (FEV1) Forced expired vol. In 1 sec during fvc maneuver. Expressed as an absolute value or % of fvc. N- FEV1 (1 SEC)- 75-85% OF FVC  FEV2 (2 SEC)- 94% OF FVC  FEV3 (3 SEC)- 97% OF FVC
  • 57. CONTINUED…… CLINICAL RANGE (FEV1) • 3 - 4.5 L • 1.5 – 2.5 L • <1 L • 0.8 L • 0.5 L PATIENT GROUP • NORMAL ADULT • MILD – MOD.OBSTRUCTION • HANDICAPPED • DISABILITY • SEVERE EMPHYSEMA
  • 58. CONTINUED…… FEV1 – Decreased in both obstructive & restrictive lung disorders. FEV1/FVC – Reduced in obstructive disorders. NORMAL VALUE IS 75 – 85 % (FEV1/FVC) < 70% OF PREDICTED VALUE – MILD OBST. < 60% OF PREDICTED VALUE – MODERATE OBST. < 50% OF PREDICTED VALUE – SEVERE OBST.
  • 59. CONTINUED…… DISEASE STATES FVC FEV1 FEV1/FVC 1) OBSTRUCTIVE NORMAL ↓ ↓ 2) STIFF LUNGS ↓ ↓ NORMAL 3 ) RESP. MUSCLE WEAKNESS ↓ ↓ NORMAL
  • 60. PEAK EXPIRATORY FLOW RATE (PEFR) - It is the max. Flow rate during fvc maneuver in the initial 0.1 sec. -PEFR DETERMINED BY : 1) Function of caliber of airways 2) Expiratory muscle strength 3) Pt’s coordination & effort - Estimated by 1) drawing a tangent to steepest part of FVC spirogram (error prone) 2) average flow during the litre of gas expired after initial 200 ml during fvc maneuver. - .
  • 61. FORCED MID-EXPIRATORY FLOW RATE (FEF25%-75%): • Maximum Mid expiratory Flow rate • Max. Flow rate during the mid-expiratory part of FVC maneuver. • Effort independent • Misnomer, as FEF25-75% decreased by 1) marked reduction in exp. Effort 2)submaximal inspiration b4 maneuver → ↓FVC → ↓ FEF25- 75% • It may decrease with truly max. Effort as compared to slightly submaximal effort as dynamic airway compression occurs with maximal effort. • N value – 4.5-5 l/sec. Or 300 l/min. • Upto 2l/sec- acceptable. • CLINICAL SIGNIFICANCE: SENSITIVE & IST INDICATOR OF OBSTRUCTION OF SMALL DISTAL AIRWAYS
  • 62. MAXIMUM BREATHING CAPACITY: (MBC/MVV) • MAX. VOLUNTARY VENTILATION  Largest volume that can be breathed per minute by voluntary effort , as hard & as fast as possible.  N – 150-175 l/min.  Estimate of max. Ventilation available to meet increased physiological demand.  Measured for 12 secs – extrapolated for 1 min.  MVV = FEV1 X 35
  • 63. CONTINUED……. • Discrepancy b/w FEV1 and MVV means inconsistent / submaximal inspiratory effort • MBC/MVV altered by- airway resistance - Elastic property -Muscle strength - Learning - Coordination - Motivation
  • 64. RESPIRATORY MUSCLE STRENGTH Evaluated by measuring max. Static resp. Pressure with anaeroid gauge • Pressures are generated against occluded airway during a max. Forced insp/exp. Effort MAX STATIC INSP. PRESSURE: (PIMAX)- • Measured when inspiratory muscles are at their optimal length i.e. at RV • PI MAX = -125 CM H2O • CLINICAL SIGNIFICANCE:  IF PI MAX< 25 CM H2O – Inability to take deep breath.
  • 65. CONTINUED……. • MAX. STATIC EXPIRATORY PRESSURE (PEMAX):  Measured after full inspiration to TLC  N VALUE OF PEMAX IS =200 CM H20  PEMAX < +40 CM H20 – Impaired cough ability  Particularly useful in pts with NM Disorders during weaning
  • 66. MEASUREMENT OF AIRWAY RESISTANCE 1) Raw- Body plethysmography 2) Forced expiratory maneuvers:  Peak expiratory flow (PEF) FEV1 3) Response to bronchodialtors (FEV1)
  • 67. Spirometry Pre and Post Bronchodilator • Obtain a flow-volume loop. • Administer a bronchodilator. • Obtain the flow-volume loop again a minimum of 15 minutes after administration of the bronchodilator. • Calculate percent change (FEV1 most commonly used---so % change FEV 1= [(FEV1 Post-FEV1 Pre)/FEV1 Pre] X 100). • Reversibility is with 12% or greater change.
  • 68. FLOW VOLUME LOOPS • Do FVC maneuver and then inhale as rapidly and as much as able. • This makes an inspiratory curve. • The expiratory and inspiratory flow volume curves put together make a flow volume loop.
  • 69. Flow-Volume Loops (Rudolph and Rudolph, 2003)
  • 70. How is a flow-volume loop helpful? • Helpful in evaluation of air flow limitation on inspiration and expiration • In addition to obstructive and restrictive patterns, flow- volume loops can show provide information on upper airway obstruction: – Fixed obstruction: constant airflow limitation on inspiration and expiration—such as in tumor, tracheal stenosis – Variable extrathoracic obstruction: limitation of inspiratory flow, flattened inspiratory loop—such as in vocal cord dysfunction – Variable intrathoracic obstruction: flattening of expiratory limb; as in malignancy or tracheomalacia
  • 71. TESTS FOR GAS EXCHANGE FUNCTION 1) ALVEOLAR-ARTERIAL O2 TENSION GRADIENT:  Sensitive indicator of detecting regional V/Q inequality  N value in young adult at room air = 8 mmhg to upto 25 mmhg in 8th decade (d/t decrease in PaO2)  AbN high values at room air is seen in asymptomatic smokers & chr. Bronchitis (min. symptoms) PAO2 = PIO2 – PaCo2 R
  • 72. CONTINUED…….. 2) DYSPNEA DIFFENRENTIATION INDEX (DDI): - To d/f dyspnea due to resp/ cardiac d’s DDI = PEFR x PaCO2 1000 - DDI- Lower in resp. pathology
  • 73. CONTINUED…… 3) DIFFUSING CAPACITY OF LUNG: defined as the rate at which gas enters into bld. divided by its driving pr. DRIVING PR: gradient b/w alveoli & end capillary tensions. Fick’s law of diffusion : Vgas = A x D x (P1-P2) T D= diffusion coeff= solubility √MW
  • 74. CONTINUED……. • DL IS MEASURED BY USING CO, COZ: A) High affinity for Hb which is approx. 200 times that of O2 , so does not rapidly build up in plasma B) Under N condition it has low bld conc ≈ 0 C) Therefore, pulm conc.≈0
  • 75. SINGLE BREATH TEST USING CO • Pt inspires a dilute mixture of CO and hold the breath for 10 secs. • CO taken up is determined by infrared analysis: • DlCO = CO ml/min/mmhg • PACO – PcCO • N range 20- 30 ml/min./mmhg. • DLO2 = DLCO x 1.23
  • 76. DLCO decreases in- • Emphysema, lung resection, pul. Embolism, anaemia • Pulmonary fibrosis, sarcoidosis- increased thickness • DLCO increases in: (Cond. Which increase pulm, bld flow)  Supine position  Exercise  Obesity  L-R shunt
  • 77. TESTS FOR CARDIOPLULMONARY INTERACTIONS • Reflects gas exchange, ventilation, tissue O2, CO. • QUALITATIVE- history, exam, ABG, stair climbing test • QUANTITATIVE- 6 minute walk test
  • 78. CONTINUED……. • 1) STAIR CLIMBING TEST: • If able to climb 3 flights of stairs without stopping/dypnoea at his/her own pace- ↓ed morbidity & mortality • If not able to climb 2 flights – high risk • 2) 6 MINUTE WALK TEST: - Gold standard - C.P. reserve is measured by estimating max. O2 uptake during exercise - Modified if pt. can’t walk – bicycle/ arm exercises - If pt. is able to walk for >2000 feet during 6 min pd, - VO2 max > 15 ml/kg/min - If 1080 feet in 1 min : VO2 of 12ml/kg/min - Simultaneously oximetry is done & if Spo2 falls >4%- high risk
  • 79. THANKYOU