1. Pulmonary Function Tests
Presenter: Dr. Sofia Patial
Moderator: Dr. Gian Chauhan

2. GOALS To predict presence of pulmonary dysfunction
To know the functional nature of disease.
To assess the severity of disease
To assess the progression of disease
To assess the response to treatment
Medicolegal- to assess lung impairment as a result of occupational hazard.
To identify patients at perioperative risk of pulmonary complications

3. 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

4. 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)

5. Contraindications: Hemoptysis of unknown origin Pneumothorax
Unstable cardiovascular status, recent MI, pulmonary embolism
Thoracic, abdominal or cerebral aneurysms
Recent eye surgery (cataract)
Nausea, vomiting
Recent surgery on thorax or abdomen

6. Components of PFT’s:
Spirometry for measuring airway mechanics (dynamic flow rates of gases)
Measuring lung volumes and capacities
Measuring diffusion capacity of lung

7. Spirometry

8. PREREQUISITIES Prior explanation to the patient
Not to smoke /inhale short acting bronchodilators 4 hrs prior or oral aminophylline and long acting bronchodilator 12hrs prior.
Remove any tight clothings/ waist belt/ dentures
Pt. Seated comfortably
If obese, child < 12 yrs- standing
Nose clip to close nostrils.
3 acceptable tracings taken & largest value is used.

9. FVC Forced vital capacity (FVC):
Total volume of air that can be exhaled forcefully from TLC
Exhalation time at least 6sec for adults & children> 10 yrs
3 sec for children< 10 years
Interpretation of % predicted:
80-120% Normal
70-79% Mild reduction
50%-69% Moderate reduction
<50% Severe reduction

10. FEV1 FEV1/FVC ratio Volume of air forcefully
expired in 1st second of FVC
N- FEV1 (1 SEC) % OF FVC
FEV2 (2 SEC)- 94% OF FVC
FEV3 (3 SEC)- 97% OF FVC
FEV1/FVC ratio
Reduced in obstructive lung diseases
<70%: mild obst,
<60% mod obst,
<50%: severe obst

12. FEF25-75
Mean forced expiratory flow in middle half of FVC
Reflect status of small airways
Effort independent expiration
N value – l/sec Or 300 l/min.
Upto 2l/sec- acceptable.
CLINICAL SIGNIFICANCE: SENSITIVE & 1st INDICATOR of obstruction of small distal airways
Interpretation of % predicted:
>79% Normal
60-79% Mild obstruction
40-59% Moderate obstruction
<40% Severe obstruction

13. PEFR max. Flow rate during initial 0.1 sec of FVC . DETERMINED BY :
Function of caliber of airways
Expiratory muscle strength
Pt’s coordination & effort
Normal value in young adults (<40 yrs) > 500L/min
Clinical significance - values of <200 L/m- impaired coughing & hence likelihood of post-op complication

14. MAXIMUM BREATHING CAPACITY: (MBC/MVV)
Largest volume that can be breathed per minute by voluntary effort , as hard & as fast as possible.
N – l/min.
Estimate of max. ventilation available to meet increased physiological demand.
Measured for 12 secs – extrapolated for 1 min.
MVV = FEV1 X 35
MVV altered by- airway resistance
- Elastic property
-Muscle strength
- Learning, Coordination, Motivation

15. RESPIRATORY MUSCLE STRENGTH
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.
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

16. Flow-Volume Loop
Illustrates maximum expiratory and inspiratory flow-volume curves
Useful to help characterize disease states (e.g. obstructive vs. restrictive)

20. Reversibility: Indicate effective therapy
Spirometry before & after bronchodilator
12% or greater improvement in FEV1 and at least 200 ml increase in FEV1 .
post FEV1-pre FEV1
% improvement= x100
Pre FEV1

21. Bronchial Challenge: Detects hyperreactive airway
Indication- patients of seasonal or exercise induced wheezing with normal spirometry results
use of agents like histamine, methacholine, cold air, exercise etc.
Start with NS aerosol- positive response: 10% or more decrease in FEV1

22. Methacholine aerosol (0.03,0.06,16mg/ml)
Positive response- 20% or more decrease in FEV1
e.g; PD22FEV1 = 4mg/ml

24. FEMALES NORMAL VALUES MALES IRV 3.3 L TV 0.5 L ERV 1.0 L RV 1-2 L
TLC L
FEMALES
1.9 L
0.5 L
0.7 L
1.1 L
4.2 L

25. 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)
PATHOLOGICAL:
disease of respiratory muscles
Abdominal condition : pain, dis. and splinting

26. DIFFERENT POSTURES AFFECTING VC
POSITION
TRENDELENBERG
LITHOTOMY
PRONE
RT. LATERAL
LT. LATERAL
DECREASE IN VC
14.5%
18%
10%
12%
in post operative period if VC falls below 3 times VC– artificial respiration is needed to maintain airway clear of secretions.

27. 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.

28. 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 - only if closing capacity is less than FRC
Keep airway resistance low (but not minimal)

30. MEASUREMENTS OF VOLUMES
TLC, RV, FRC – MEASURED USING
Nitrogen washout method
Inert gas (helium) dilution method
Total body plethysmography

31. 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
As no helium is lost; (as He is insoluble in blood)
C1 X V1 = C2 ( V1 +V2)

32. 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

33. DIFFERENCE BETWEEN THE TWO METHODS:
In healthy people there is very little difference.
Gas dilution technique measures only communicating gas volume.
Thus,
Gas trapped behind closed airways
Gas in pneumothorax
=> are not measured by gas dilution technique, but measured by body plethysmograph

34. 3) N2 WASH OUT METHOD:
Following a 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 calculated.

35. PROBLEMS WITH N2 WASH OUT METHOD
Atelectasis may result from washout of nitrogen from poorly ventilated lung zones (obstructed areas)
Elimination of hypoxic drive in CO2 retainers is possible
Underestimates FRC due to underventilation of areas with trapped gas

36. 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

37. 2) DYSPNEA DIFFENRENTIATION INDEX (DDI):
To differentiate dyspnea due to resp/ cardiac disease
DDI = PEFR x PaCO2
1000
DDI- Lower in resp. pathology

38. 3) DIFFUSING CAPACITY OF LUNG:
depends upon gradient and thickness of alveolo-capillary membrane.
defined as the rate at which gas enters into blood divided by its driving pressure.
DRIVING PRESSURE: gradient b/w alveoli & end capillary tensions.
DL CO = Vco /(P A CO–P c CO)

39. 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
N range ml/min./mmhg.
NORMAL % of predicted
DL IS MEASURED BY USING CO, coz:
High affinity for Hb which is approx. 210 times that of O2 , so does not rapidly build up in plasma
Therefore, pulm capillary partial pressure of CO ≈ 0

40. 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

41. TESTS FOR CARDIOPLULMONARY INTERACTIONS
Reflects gas exchange, ventilation, tissue O2.
QUALITATIVE- history, exam, ABG, stair climbing test
QUANTITATIVE- 6 minute walk test

42. 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
Quantitative assessment by measuring the max O2 uptake during exercise(VO2max).
A 2-flight stair climb (20 steps/min) without dyspnea is approx VO2max of 16ml/kg/min.
VO2max≥20ml/kg/min: minimal risk
VO2max≤15ml/kg/min: inc cardiopulmonary risk
VO2max≤10ml/kg/min: high risk with 30% mortality

43. 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 6min( 180 feet in 1 min): VO2 of 12ml/kg/min
Simultaneously oximetry is done & if Spo2 falls >4%- high risk

44. BED SIDE PFT 1).Sabrasez breath holding test: 15-25 sec- limited CPR
>25 sec.-normal
15-25 sec- limited CPR
<15 sec- very poor CPR (Contraindication for elective surgery)
SEC ml VC
20 – 25 SEC ml VC
SEC ml VC
SEC ml VC
SEC ml VC

45. 3). FET (WATCH AND STETHOSCOPE TEST ):
2). SINGLE BREATH COUNT:
It is a measure of the FRC.
> : normal
< : dec reserve
: mild impairment
: mod impaired
< : severe impairment
3). FET (WATCH AND STETHOSCOPE TEST ):
After deep breath, exhale maximally and forcefully & keep stethoscope over trachea & listen.
N. – 3-5 SECS.
OBS.LUNG DIS. - > 6 SEC
RES. LUNG DIS.- < 3 SEC

46. 4) SCHNEIDER’S MATCH BLOWING TEST: Measures MBC
Ask to blow a match stick from a distance of 6” (15 cms) with-
Mouth wide open, Chin rested, No purse lipping
No head movement, No air movement in the room
Mouth and match at the same level
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.

47. 5) GREENE & BEROWITZ 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.
wet productive cough / self propagated paraoxysms of coughing – patient susceptible for pulmonary Complication.

48. 6) WRIGHT PEAK FLOW METER: Measures PEFR N – MALES- 450-700 L/MIN
6) WRIGHT PEAK FLOW METER: Measures PEFR N – MALES L/MIN. FEMALES L/MIN. <200 L/min.–inadequate cough efficiency.

49. 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 intensity of whistle disappears.
At the last position at which the whistle can be blown , the PEFR can be read off the scale.

50. 8)Wright respirometer : measures TV, MV (15 secs times 4)
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 position.
MV- instrument record for 1 min. And read directly
TV-calculated and dividing MV by counting Respiratory Rate.
Accurate measurement in the range of l/min.(±10%)
USES: 1)bed side PFT
2) ICU – weanig pts. from ventilation.
9) BED SIDE PULSE OXIMETRY
10) ABG.

57. THANK YOU