pulmonary%20function%20test%20-%20Copy.pptx

PULMONARY FUNCTION TEST

1. Pulmonary Function Test

2. INDICATIONS

3. Clinical & bedside Wright’s respirometer, PEFR Spirometry Resistance/compliance/diffusing capacity ABGs, capnometry Staircase, 6-min walk, CPET

4. PRE PFT EVALUATION AND IDENTIFICATION

5. BED SIDE LUNG FUNCTION TESTS

6. SABRAZES'S BREATH HOLDING TEST By Sabrazes, in 1902 (Bordeaux): also called Voluntary Apnoeic Pause Time for which a person can hold his breath, after a deep inspiration "Cardio-respiratory Reserve of the Patient“ >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 (normal-3100-4800ml) 20 – 25 SEC - 3000 ml VC 15 - 20 SEC - 2500 ml VC 10 - 15 SEC - 2000 ml VC 5 - 10 SEC - 1500 ml VC

7. SCHNEIDER'S MATCH BLOWING TEST A lighted candle at the level of patient's mouth (sitting) Minimum Distance, ability to blow it off: 25 cm. <15 cm -" Reduced Peak Expiratory Flow " 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 (N-150-175 L/min) 9”inch >150 L/MIN. 6”inch >60 L/MIN. 3”inch > 40 L/MIN.

8. DE BONO' S (DEBONO' S) WHISTLE Measures P E F by threshold activation Plastic tube with kettle type whistle at one end and leak hole at other side 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

9. COUGH TEST : DEEP BREATH F/BY COUGH ABILITY TO COUGH STRENGTH EFFECTIVENESS - VC ~ 3 TIMES TV FOR EFFECTIVE COUGH. A wet productive cough / self propagated paroxysms of coughing – patient susceptible for pulmonary Complication. AUSCULATION (WHEEZE TEST) Patient asked to take 5 deep breaths, then auscultated to check presence or absence of wheeze.

10. WRIGHT RESPIROMETER measures TV, MV Simple and rapid Can be connected to endotracheal tube or face mask Prior explanation to patients needed. Ideally done in sitting position MV- instrument records for 1 min and reads directly . TV-calculated by dividing MV by counting Respiratory Rate .

11. SPIROMETER AND SPIROMETRY Static : 4 Volumes 4 Derived Capacities (Sum of 2 or more lung volumes) Dynamic : FEV1,PEFR, MBC, etc., (timed-rated) Four Lung volumes : Tidal volume Inspiratory reserve volume Expiratory reserve volume Residual volume Five capacities : Inspiratory capacity Expiratory capacity Vital capacity Functional residual capacity Total lung capacity Addition of 2 or more Volumes comprises a Capacity

12. TIDAL VOLUME (TV) AND MINUTE VENTILATION "Vol of air inspired expired during normal quiet breathing“ N : 500 ml (6-8ml /kg) Minute Ventilation TV X RR = Min. Ventilation = 3.7 – 20 L/min (TV-VD) x RR = Alv.Ventilation = 2- 3.5 L/min/cm2

13. ALVEOLAR VENTILATION (VA) That part of MV that takes part in gas exchange Affected by TV, RR, Vd and controls the excretion of CO2 VD : VD Anatomical / VD Physiological / VD Aparatures Deep anesthesia, respiratory dep. drugs decrease VA Hence, among other factors, this mandates an FiO2 of atleast 0.33

14. INSPIRATORY RESERVE VOLUME (IRV) Maximum amount of air that can be inhaled after a normal tidal volume inspiration (N: 1900-3300 ml) EXPIRATORY RESERVE VOLUME (ERV) Maximum amount of air that can be exhaled from the resting expiratory level (N : 700- 1100 ml) INSPIRATORY CAPACITY (IC) Maximum amount of air that can be inhaled from the end of a tidal volume (IRV+ TV) ( N: 2400-3500 ml)

15. RESIDUAL VOLUME (RV) Volume of air remaining in the lungs at the end of maximum expiration N- 20-25ml/kg (1200-1500) (Air not removed even by forceful expiration) FUNCTIONAL RESIDUAL CAPACITY (FRC) Volume of air remaining in the lungs at the end of a TV expiration FRC =ERV+ RV= 1100+1200 N: 2300 ml

16. RV AND FRC: NOT MEASURABLE BY SPIROMETRY Measured by indirect methods : 1. N2 washout 2.He wash-in 3.Body Plethysmography RV, TLC & FRC all contain a fraction, the R V which cant be detected by simple spirometry : If one is measured, others are easily derived Increase FRC : means inadequate lung emptying Increase RV : may be ass. with increase work of breathing

17. FRC Increase Temporary increase : Br. Asthma or overinflation of lungs after thoracotomy Emphysema with air trapping, chronic bronchitis, & due to PEEP application Decrease Induction of anesthesia, Post op., esp. after abd . Surgeries 1.Reservoir of 02 increase by pre-oxygenation &, prevents hypoxemia during apnoea -- Pregnancy, neonates (Low FRC) 2.Determines speed of induction with inhalational agents

18. TOTAL LUNG CAPACITY (TLC) Volume of air in the lungs after a maximum inspiration TLC = IRV + TV + ERV + RV 3000 + 500 + 1100 + 1200 = 5800 ml (80-100 ml/kg)

19. VITAL CAPACITY VC Maximal volume of gas that can be expelled from the lungs by a forceful effort following a maximal inspiration VC =TV+IRV+ERV= 500 + 3000 + 1100= 4600 ml (60-70 ml/kg) Preoxygenation : 2-3 VC breaths = 2-3 minutes of Tidal breathing

20. VC IS AFFECTED BY Physical dimensions- directly proportional to height SEX – More in males : large chest size, more muscle power. 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) PuL Disease and Pul . Congestion Space occupying lesions in the chest Abdominal Tumours / abd pain ( aff . Diaphr.movement )

21. CLINICAL SIGNIFICANCE OF VC VC correlates with capability for deep breathing and effective cough. So in Post Operative period if VC falls below 3 times TV– Artificial Respiration is needed to maintain airway clear of secretions.

22. CONTRAINDICATIONS TO PERFORMING PFTS Myocardial infarction within the last month unstable angina Recent thoraco-abdominal surgery Recent ophthalmic surgery Thoracic or abdominal aneurysm Current pneumothorax

23. FORCED EXPIRATORY VOLUME IN ONE SECOND (FEV1) percentage of FVC which can be forcibly expired as rapidly as possible in one second after maximal inspiration" N : 80% of FVC & Dependent on Voluntary Effort 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 Decrease in chronic bronchitis -- Indirect measure of MBC -- Easier to obtain in ill patients, unlike MBC FEV 1 /FVC (FEV 1%) - percentage of total FVC expelled from lung during 1st second of forced exhalation

24. PEAK EXPIRATORY FLOW RATE (PEFR) Max flow rate achieved during FVC maneuver after full inspiration wih maximal expiration PEFR = 4-5xMB N: 450-700 It/min (M) 300-500 lt /min (F) Tangent to steepest part of FVC curve Clinical significance - values of <200L/min- impaired coughing & hence likelihood of post-op complication

25. FEF - Forced Expiratory Flow Measures how much air can be expired from the lungs FVC curve - split into 4 quartiles; FEF 25%, FEF 50%, FEF 75% of FVC FEF 25% - amount of air forcibly expelled in first 25% of FVC test FEF 50% - during first half (50%) of FVC test FEF 25%-75% - during middle half of FVC test (MMFR) Reduved in obstructive disease pt. independent Indicator for small airways disease

26. MVV - MAXIMAL VOLUNTARY VENTILATION Total volume of air moved out of lungs over one min 100-120 L/min Dynamic test as opposed to the VC (static test) Patient breathes in & out as rapidly & fully as possible for 12-15 seconds X 3-4 Difficult for ill or post operative patients Reflects status of respiratory muscle, compliance of thorax­, lung complex, airway resistance

27. Poor performance; predicts post-op. pulmonary problems due to muscle weakness Effort dependent, poor predictor of true pulmonary strength & compliance Reduced in old age, emphysema, bronchospasm/ bronchiolar obstn . MVV= 35 x FEV1 PEFR : 4-5 times MBC

28. FLOW-VOLUME LOOPS Graphic Analysis is of flow at various lung volumes 1. subject inhale fully to TLC then perform an FVC maneuver, 2. Maximal exhalation as fast as possible Flow & Volume traced on an X-Y axis simultaneously Effort dependent & independent areas Mid VC flow ratio: Expiratory FIow to Inspiratory Flow at 50% of VC = 1.0

29. OBSTRUCTIVE Limitation of expiratory airflow as airways cannot empty as rapidly compared to normal (e.g., narrowed airways from bronchospasm, inflammation, etc.) Examples: Asthma/ Emphysema/ Cystic Fibrosis RESTRICTIVE Characterized by reduced lung volumes/decreased lung compliance Examples: Interstitial Fibrosis/ Scoliosis/ Obesity/ Lung Resection/ Neuromuscular diseases/ Cystic Fibrosis

30. CLOSING CAPACITY Lung vol at which airways in dependent area of lung begin to close/ stop contributing to expired gas⇒ Air Trapping occurs Airway narrowing due to gravitational forces, tested by Single breath N2 washout technique Relationship of CC to FRC: If CC rises > FRC during part or later perhaps the whole of normal range of ventilation, blood passing through the closed areas of lung will not be fully oxygenated, and PaO2 will fall

31. CV+RV=CC Increase CC is seen in Smokers Rapid IV transfusion LVF and foll . M I Obesity Early ch. bronchitis After surgery may contribute to post op. hypoxemia (PEEP may help by increasing FRC above CC )

32. RESISTANCE, COMPLIANCE, DIFFUSING CAPACITY Respiratory Muscle Strength Resistance Compliance Diffusing Capacity A-a P02 Difference Pa02

33. RESPIRATORY MUSCLE STRENGTH Affects PFTs requiring patient effort FVC, FEV1, peak flow, MVV Max. static inspiratory pressure ( Plmax ) Max static expiratory pressure ( PEmax )

34. Not measured routinely Particularly useful in evaluation of patients with NM disorders Can readily identify patients in whom respiratory muscle weakness is prime Cause of hypercapnic respiratory failure Extubation Criteria after GA & Weaning From MV : PImax at least -20 to - 30 cm H2O

35. RESISTANCE "Difference between atmospheric pressure & alveolar pressure“ Balance between intrapleural pressures & elastic recoil of lung Dynamic compression of small airways occurs when intra­pleural pressures increase (compared to intraluminal pressures) to about 40 cm H20 during forced expiration Severe - narrowing or closure of bronchioles occurs If airway closure is premature, CV will encroach on FRC

36. Airway resistance (Raw) determined by size of the airways Raw is greatest at RV & least at TLC because, airways are Smallest at RV Largest at high lung volumes Airway conductance ( Gaw ) Reciprocal of Raw - linearly related to lung volume Used to identify bronchoconstriction or bronchodilation

37. COMPLIANCE Describes elastic properties of various parts of respiratory system ‘”Volume change per unit change in pressure" (200 ml/cm H2O in normal lung) Total respiratory compliance = lung + chest wall compliance N 70-80 ml/ cm H20 Two components Static compliance (alveolar stretchability) - measured when there is no flow activity at end of inspiration Dynamic compliance - measures change in volume as pressure changes during actual gas flow through the respiratory cycle

38. Static compliance curve can be used to select the ideal level of PEEP for a patient in the ICU Ideal PEEP: Corresponds to a point on favorable part of pressure volume curve for alveoli, maximizing oxygenation & minimizing over-distension

39. DIFFUSING CAPACITY OF LUNG (DL- DLCO) Diffusion from alveoli to capillaries: rate at which a gas enters blood divided by its driving pressure Driving Pressure: gradient between alveolar & end-capillary tensions N: 'Diffusion factor' for DLCO : 20-30 mL/min/mm Hg Determined by : Patient inhales nontoxic low concentrations of CO with He (single­-breath test) holds breath for 10 seconds

40. Decreases in DLCO: Emphysema, lung resection pulmonary emboli anemia, decrease surface area by reducing capillary blood volume Pulmonary fibrosis, sarcoidosis, alveolar proteinosis, increase alveolar wall thickness Increased DLCO rarely of much clinical concern when there is increase pulmonary blood volume E.g. the supine position, exercise, obesity, L-to-R shunts

41. Tests of Gas Exchange Function Alveolar-arterial oxygen tension difference N: 8 - 25 mm Hg & and increase with age Not widely used because of difficulty in measuring PAO2 which must be estimated from alveolar air equation Arterial 02 tension (Pa02) in room air Useful estimate of lung function Value <60 mm hg indicates significant if not advanced lung disease Decrease in drug induced hypoventilation

42. Why PF studies are required during preoperative evaluation? To detect : decrease Lung volumes, rapid & shallow breathing, impaired gas exchange Anesthetic procedure Surgical procedure Body position Drugs More in patients with compromised pulmonary function Which tests to Do? No single test appears to be best predictor of risk, probably because none assesses all of the factors that are important regardless of whether complications may occur or not

43. Which patients are candidates for pre op PFT? TISI Guidelines Age> 70 Morbid obesity Thoracic surgery Upper abdominal surgery History of smoking, cough Any pulmonary disease What will be the best scheme of PFTs ? FEV1, FVC, FEV1 /FVC, peak flow, FEF 25%-75% (single spirometric study) along with arterial blood gas analysis The American college of chest physicians Lung resection Smoking history, dyspnea Cardiac surgery Upper abdominal surgery Lower abdominal surgery Uncharacterized pulmonary symptoms

44. P F CRITERIA INDICATING INCREASED RISK FOR POST OP COMPLICATIONS FROM RESPIRATORY FAILURE