Pulmonary function tests

important discussion and anaesthesia related stuff

1. Dr YOGESH RATHOD DEPT OF ANESTHESIA KEM HOSPITAL MUMBAI PULMONARY FUNCTION TESTS

2. PULMONARY FUNCTION TESTS Includes a wide variety of Objective tests to assess lung function. Provides Standardized measurements for assessing the presence and severity of Respiratory dysfunction.

3. GOALS To predict the presence of pulmonary dysfunction To know the functional nature of disease (Obstructive or Restrictive) To assess the severity and progression of disease To identify patients at Perioperative risk of Pulmonary complications

4. INDICATIONS OF PFT IN PAC TISI GUIDELINES FOR PREOPERATIVE SPIROMETRY Age > 70 yrs. Morbid obesity Thoracic surgery Upper abdominal surgery Smoking history and cough Any pulmonary disease

5. INDICATIONS FOR PREOPERATIVE SPIROMETRY ACP GUIDELINES FOR PREOPERATIVE SPIROMETRY Lung resection H/o smoking, dyspnoea Cardiac surgery Upper abdominal surgery Lower abdominal surgery Uncharacterized pulmonary disease (defined as history of pulmonary Disease or symptoms and no PFT in last 60 days)

6. Lung Volumes and Capacities 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 .

7. TIDAL VOLUME (TV) Volume of air inhaled/ exhaled in each breath during quite respiration. N – ~6-8 ml/kg. TV FALLS WITH- 1. Decrease in compliance 2. Decreased ventilatory muscle strength

8. INSPIRATORY RESERVE VOLUME (IRV) Maximum volume of air which can be Inspired after a Normal Tidal inspiration i.e. from end inspiration point. N- 1900 ml- 3300 ml.

9. EXPIRATORY RESERVE VOLUME (ERV) Maximum Volume of air which can be expired after a normal tidal expiration i.e. from end expiration point N- 700 ml – 1000 ml

10. RESIDUAL VOLUME (RV) Volume of air remaining in the lungs after a maximum expiration. N- 20-25ml/kg (1700- 2100 ml) Indirectly measured- FRC-ERV Cannot be measured by Spirometry

11. INSPIRATORY CAPACITY (IC) Maximum volume of air which can be inspired after a normal tidal expiration. IC = TV + IRV N-2400 ml – 3800 ml Detects extrathoracic airway obstruction Changes parallel changes in VC

12. VITAL CAPACITY (VC) Maximum volume of air expired after a maximum Inspiration VC= TV+ERV+IRV N- 3100ml-4800ml (60-70 ml/kg)

13. VITAL CAPACITY- CONTD Coined by John Hutchinson VC is considered abnormal if ≤ 80% of predicted value Factors Influencing VC PHYSIOLOGICAL : 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)

14. FACTORS DECREASING VC 1. Alteration in muscle power- d/t drugs, n-m diseases. 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 .

15. 5. Depression of respiration : Opioids / Volatile agents 6. Abdominal Splinting – Abdominal binders, tight bandages, hip spica . 7.Abdominal pain – decreases by 50% & 75% in lower & upper abdominal Surgeries respectively. 8. Posture

16. DIFFERENT POSTURES AFFECTING VC POSITION DECREASE IN VC TREDELENBERG 14.5% LITHOTOMY 18% PRONE 10% RT LATERAL 12% LT LATERAL 10%

17. 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.

18. FUNCTIONAL RESIDUAL CAPACITY (FRC) Volume of air remaining in the lungs after normal tidal expiration. N- 2300ml -3300ml or 30-35 ml/kg FRC = RV + ERV Decreases under anaesthesia - -With Spontaneous Respiration – decreases by 20% -With paralysis – decreases by 16%

19. FACTORS AFFECTING FRC FRC increases with- Increased height Erect position (30% more than in supine) Decreased lung recoil ( e.G. Emphysema)- Gas Trapping FRC decreases with- Obesity Muscle paralysis (especially in supine) Supine position Pleural Effusion Restrictive lung disease ( e.G. Fibrosis, pregnancy) Anaesthesia FRC does NOT change with age.

20. 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

21. TOTAL LUNG CAPACITY (TLC) Maximum volume of air attained in lungs after maximal inspiration. N- 4000ml-6000ml or 80-100 ml/kg TLC= VC + RV

22. DEFINITIONS Forced Vital Capacity(FVC)- Max vol. of air which can be expired out as forcefully and rapidly as possible, following a maximal inspiration. Normal healthy subjects have VC = FVC. 2. FORCED VITAL CAPACITY IN 1 SEC. (FEV1)- Forced expired volume 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

23. CLINICAL RANGE(FEV1) PATIENT GROUP 3 - 4.5 L 1.5 – 2.5 L <1 L 0.8 L 0.5 L NORMAL ADULT MILD.OBSTRUCTION MOD.OBSTRUCTION HANDICAPPED DISABILITY SEVERE EMPHYSEMA

24. FEV1 – Decreased in both obstructive & restrictive lung disorders. FEV1/FVC – Reduced in obstructive disorders. NORMAL VALUE (FEV1/FVC) 75 – 85 % < 70% of predicted value – Mild obstruction < 60% of predicted value – Moderate obstruction < 50% of predicted value – Severe obstruction

25. DISEASE STATES FVC FEV1 FEV1/FVC OBSTRUCTIVE NORMAL ↓ ↓ 2) STIFF LUNGS ↓ ↓ NORMAL 3 ) RESP. MUSCLE WEAKNESS ↓ ↓ NORMAL

26. PEAK EXPIRATORY FLOW RATE (PEFR) It is the maximum flow rate during FVC maneuver in the initial 0.1 sec. Normal value in young adults (<40 yrs)= 500l/min Clinical significance - values of < 200 l/min - impaired coughing & hence likelihood of post-op complication

27. FORCED MID-EXPIRATORY FLOW RATE (FEF25%-75%): Maximum flow rate during the mid-expiratory part of FVC maneuver. value – 4.5-5 l/sec. Or 300 l/min. CLINICAL SIGNIFICANCE: SENSITIVE & IST INDICATOR OF OBSTRUCTION OF SMALL DISTAL AIRWAYS

28. MAXIMUM BREATHING CAPACITY: (MBC/MVV) Largest volume that can be breathed per minute by voluntary effort , as hard & as fast as possible. N – 150-175 l/min. Measured for 12 secs – extrapolated for 1 min. MVV(max voluntary ventilation) = FEV1 X 35 Discrepancy b/w FEV1 and MVV means inconsistent / submaximal inspiratory effort MBC/MVV altered by- airway resistance - Elastic property -Muscle strength - Learning - Coordination - Motivation

29. BED SIDE PFTS 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 (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

30. 2) Single breath count: After deep breath, hold it and start counting till the next breath. Indicates vital capacity N- 30-40 COUNT BED SIDE PFTS

31. 3) SCHNEIDER’S MATCH BLOWING TEST: (MEASURES Maximum Breathing Capacity) Ask the patient 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 BED SIDE PFTS

32. 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” >150 L/MIN. 6” >60 L/MIN. 3” > 40 L/MIN. BED SIDE PFTS

33. 4) 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. 5) WHEEZE TEST : Patient asked to take 5 deep breaths, then auscultated between shoulder blades to check presence or absence of wheeze. BED SIDE PFTS

34. 6) 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 7) DEBONOs 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 . BED SIDE PFTS

35. DEBONO’S WHISTLE

36. 8) 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. 9) BED SIDE PULSE OXIMETRY 10) ABG.

37. CATEGORIZATION OF PFTs 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.

38. 2) GAS- EXCHANGE TESTS: A) Alveolar-arterial pO2 gradient B) Diffusion capacity C) Gas distribution tests -Single breath N 2 test. - Multiple Breath N 2 test - Helium dilution method. D) Ventilation – Perfusion tests A) ABG B) single breath CO elimination test CATEGORIZATION OF PFTs

39. 3) CARDIOPULMONARY INTERACTION: A) Qualitative tests: - History , Examination - ABG - Stair Climbing Test B) Quantitative tests - 6 min Walk test (Gold standard) CATEGORIZATION OF PFTs

40. 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

41. 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

42. Measurements Obtained from the FVC Curve FEV 1 ---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 FEV 1 /FVC---the ratio of FEV1 to FVC X 100 (expressed as a percent); a n important value because a reduction of this ratio from expected values is specific for obstructive rather than restrictive diseases

43. OBSTRUCTIVE DISORDERS RESTRICTIVE DISORDERS 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 Characterized by reduced lung volumes/decreased lung compliance Examples : Interstitial Fibrosis Scoliosis Obesity Lung Resection Neuromuscular diseases Cystic Fibrosis Spirometry Interpretation: Obstructive vs. Restrictive Defect

44. Obstructive Disorders FVC normal or ↓ FEV1 ↓ FEF25-75% ↓ FEV1/FVC ↓ TLC normal or ↑ Restrictive Disorders FVC ↓ FEV1 ↓ FEF 25-75% normal to ↓ FEV1/FVC normal to ↑ TLC ↓

45. Normal vs. Obstructive vs. Restrictive

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. 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 Spirometry Interpretation: What do the numbers mean?

48. 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. 1) N2 WASH OUT METHOD Patient breathes in 100% oxygen and on expiration all nitrogen is washed out. The exhaled volume and nitrogen conc. in it is measured. The difference in nitrogen volume at the initial concentration and at the final exhaled concentration allows a calcul;ation of the intrathoracic volume, usually the FRC

51. 2) 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 He 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

52. 3) 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

53. MEASUREMENT OF AIRWAY RESISTANCE 1) Body Plethysmography 2) Forced expiratory maneuvers: Peak expiratory flow (PEFR) FEV1 3) Response to bronchodilators (FEV1)

54. Patients with small airway obstruction tested twice- before and after administration of bronchodilators to evaluate responsiveness. If 2 out of 3 measurements improve, patient has a reversible airway obstruction that is responsive to medication. FVC- increase of 10% or more FEV1- increase of 200ml or 15% of baseline FEF25%-75%- increase of 20% or more Spirometry Pre and Post Bronchodilator

55. FLOW VOLUME LOOPS Do FVC maneuver and then inhale as rapidly and as much as possible This makes an Inspiratory curve. The Expiratory and Inspiratory Flow Volume Curves put together make a Flow Volume Loop.

56. TESTS FOR GAS EXCHANGE FUNCTION 1) ALVEOLAR-ARTERIAL O2 TENSION GRADIENT : Sensitive indicator of detecting regional V/Q inequality Normal value in young adult at room air = 8-25 mm Hg. Abnormal high values at room air is seen in asymptomatic smokers & chr . Bronchitis.

57. 2)DIFFUSING CAPACITY OF LUNG : - defined as the rate at which gas enters into blood. DL IS MEASURED BY USING CO: High affinity for Hb which is approx. 200 times that of O2 , so does not rapidly build up in plasma Under N condition it has low blood conc ≈ 0 Therefore, pulm conc.≈0

58. 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 – PaCO N range 20- 30 ml/min./ mmhg SINGLE BREATH TEST USING CO

59. DLCO decreases in- Emphysema, lung resection, Pul . Embolism, Anaemia Pulmonary fibrosis, sarcoidosis - increased thickness DLCO increases in: (Cond. Which increase pulmonary blood flow) Supine position Exercise Obesity L-R shunt

60. TESTS FOR CARDIOPLULMONARY INTERACTIONS Reflect gas exchange, ventilation, tissue O2, CO2. QUALITATIVE- History, examination, ABG, Stair climbing test QUANTITATIVE- 6 minute walk test

61. 1) STAIR CLIMBING TEST : If able to climb 3 flights of stairs without stopping/ dyspnoea - ↓ 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 VO2 max > 15 ml/kg/min If 1080 feet in 6 mins : VO2 of 12ml/kg/min Simultaneously oximetry is done & if Spo2 falls >4%- high risk

62. PREDICTION OF POSTOPERATIVE PULMONARY COMPLICATIONS 1) Nunn and Miledge criteria: a. FEV1<1L, N PaO2, PaCO2- Low risk of POPC b. FEV1<1L, Low PaO2, N PaCO2- patient will need prolonged O2 supplementation c. FEV1<1L, Low PaO2, High PaCO2- patient may need postop ventilation 2) Based on Spirometry : a. Predicted FVC< 50% b. Predicted FEV1 < 50% or <2 L c. Predicted MVV <50% or < 50L/min

63. PATIENT WITHOUT CHEST OPTIMIZATION FOR GENERAL ANESTHESIA IS AN EXTRA BURDON ON ANESTHETIST…….!

64. Thanks! Any Questions?