Pulmonary function tests provide objective measurements of lung function to assess respiratory dysfunction. They can predict and characterize pulmonary disease as obstructive or restrictive. Key tests measure vital capacity, forced expiratory volume in one second, and other lung volumes and capacities. Abnormal values help determine disease severity and perioperative risk. Spirometry is the cornerstone test, using flow-volume curves and spirograms to distinguish obstructive from restrictive patterns. Bedside tests also evaluate cough strength, wheezing, and breathing capacity.

1. BY
DR VISHAL KR.
KANDHWAY
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 wean patient from Ventilator in ICU
 To identify patients at Peri-operative risk of
Pulmonary complications

4. INDICATIONS FOR PREOPERATIVE
SPIROMETRY
 ACCP 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. 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.

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

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

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

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

10. INSPIRATORY CAPACITY (IC)
 Maximum volume of air
which can be inspired
after a normal tidal
expiration.
 IC = TV + IRV
 Normal-2400 ml – 3800 ml
 Detects extra-thoracic
airway obstruction

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

12. 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)

13. FACTORS DECREASING VC
1. Alteration in muscle power- 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.

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

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

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

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

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

19. FUNCTIONS OF FRC
Oxygen store
Buffer for maintaining a steady arterial po2
Partial inflation helps prevent atelectasis
Minimize the work of breathing
Minimize pulmonary vascular resistance
Minimize V/Q mismatch
Keeps airway resistance low

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

21. DEFINITIONS
1. 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
 Normal- FEV1 (1 SEC)- 75-85% OF FVC

22. 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

23.  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

24. 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)= 500 L/min
 Clinical significance - values of <200/L- impaired
coughing & hence likelihood of post-op complication

25. 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 &
INITIAL INDICATOR OF OBSTRUCTION OF
SMALL DISTAL AIRWAYS

26. MAXIMUM BREATHING CAPACITY:
(MBC/MVV)
 Largest volume that can be breathed per minute by
voluntary effort , as hard & as fast as possible.
 Normal – 150-175 l/min.
 Measured for 12 sec
MVV(max voluntary ventilation) = FEV1 X 35
 MBC/MVV altered by- Airway resistance
- Elastic property
-Muscle strength

27. BED SIDE PFTS
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 (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

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

29. 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

30.  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

31. 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

32. 6) FORCED EXPIRATORY TIME:
After deep breath, exhale maximally and forcefully & keep
stethoscope over trachea & listen.
Normal – 3-5 SECS.
OBS.LUNG DIS. - > 6 SEC
RES. LUNG DIS.- < 3 SEC
7) DEBONO’s 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

33. DEBONO’S WHISTLE

34. 8) Wright Respirometer : measures TV, MV
 Simple and rapid
 Can be connected to ETT
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.

35. 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

36. 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

38. OBSTRUCTIVE DISORDERS RESTRICTIVE DISORDERS
 Limitation of expiratory
airflow as airways cannot
empty as rapidly compared
to normal (eg 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

39.  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 ↓

40. Normal vs. Obstructive vs. Restrictive

41. 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

42. 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?

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

44. 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 calculation of
the intrathoracic volume, usually the FRC

45. 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

46. 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.

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

48.  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.
1) FVC- increase of 10% or more
2) FEV1- increase of 200ml or 15% of baseline
3) FEF25%-75%- increase of 20% or more
Spirometry Pre and Post Bronchodilator

49. 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.

51. 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.
 AbN high values at room air is seen in asymptomatic
smokers & chr. Bronchitis.

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

53.  Pt inspires a dilute mixture of CO and hold the
breath for 10 secs.
 CO taken up is determined by infrared analysis
 N range 20- 30 ml/min./mmhg
SINGLE BREATH TEST USING CO

54. 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

55. TESTS FOR CARDIOPULMONARY INTERACTIONS
 Reflects gas exchange, ventilation, tissue O2, CO2.
 QUALITATIVE-
History, examination, ABG, Stair climbing test
 QUANTITATIVE- 6 minute walk test

56.  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

57. 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

58.  3) Based on Patient criteria and type of surgery-
a. Patient dependent factors- Current Smoker, age> 70yrs,
reduced health status- ASA grade > 2, known COPD patients.
b. Surgery dependent factors- Abdominal surgery (open >minimal
invasive), thoracic surgery, long duration of
anaesthesia(>4hours), general anaesthesia (vs regional
anaesthesia)

59. REFERENCES
 Millers Anaesthesia
 Clinical Barash