Pulmonary function tests (PFTs) objectively assess lung function using tests such as spirometry, lung volume measurements, and diffusing capacity measurements. PFTs can predict, diagnose, and monitor pulmonary dysfunction. They can distinguish between obstructive and restrictive lung diseases and determine disease severity and treatment responses. PFTs also assess surgical risk and postoperative pulmonary complications. Simple bedside tests include breath counts, cough strength tests, and peak flow measurements. Laboratory PFTs precisely measure volumes, flows, gas exchange, and generate flow-volume loops. Proper interpretation of PFTs involves comparing values to predicted normals.

1. PULMONARY FUNCTION
TESTS
Dr. M HELMI AFIFIDr. M HELMI AFIFI
(MBBCh,MS,MD,MHA)(MBBCh,MS,MD,MHA)
Prof. of Anaesthesia & Intensive CareProf. of Anaesthesia & Intensive Care
Menoufiya University, EgyptMenoufiya University, Egypt

2. Pulmonary Function Tests
• A wide variety of objective tests to assess
lung function
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3. 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.

4.  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……..

5. INDICATIONS FOR PREOPERATIVE
SPIROMETRY
• ACP GUIDELINES
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. BED SIDE PFT
Single breath count:
After deep breath, hold it and start counting till the
next breath.
 N- 30-40 COUNT
 Indicates vital capacity

7. BED SIDE PFT
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

8. • 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.

9. BED SIDE TEST
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.

10. BED SIDE PFT
WRIGHT PEAK FLOW
METER:
Measures PEFR
N: M- 450-700 L/min
F- 350-500 L/min

11. Wright respirometer
measures TV, MV (15 secs times 4)
• Simple and rapid
• Instrument- compact, light and portable.
• Disadvantage: under- reads at low flow rates
and over- reads at high flow rates.
• Can be connected to endotracheal tube or
face mask
• MV- instrument record for 1 min and read
directly
• TV-calculated and dividing MV by counting
Respiratory Rate.
• Accurate measurement in the range of 3.7-
20l/min.(±10%)
• USES: 1)BED SIDE PFT
• 2) ICU – WEANIG PTS. FROM
Ventilation.

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27. INTERPRETATION
General rule:
When flow is ↓→ lesion is obstructive.
When volume is↓→ lesion is restrictive.

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31. Flow-Volume Loops
Two ways to
record results of
FVC:
•Flow-volume
curve
•Classic spirogram:
volume as a
function of time

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35. Normal vs. Obstructive vs. Restrictive
(Hyatt,
2003)

36. Flow Volume Loops
• Inspiratory loops can also be obtained to
evaluate for the presence of large airway
obstruction
• Theory changes in pressure outside and
inside the thoracic cage will cause changes in
airway diameter
• These airway changes can cause a limitation
to airflow if large enough

37. Extrathoracic Obstruction

38. Intrathoracic Obstruction

39. Fixed Obstruction

40. Large Airway Obstruction

42. MEASUREMENTS OF VOLUMES
• TLC, RV, FRC – MEASURED USING
Nitrogen washout method
Inert gas (helium) dilution method
Total body plethysmography
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43. Helium Dilution Technique
• Uses an inert gas, helium and by a closed
circuit technique, allow it to come to
equilibrium and FRC is measured
• May underestimate lung volumes in bullous
lung disease

46. Nitrogen Washout
• Determine FRC by multiple breath open circuit
nitrogen washout
• Involves having nitrogen in patients lung being
washed out by inhaling 100% O2 for several
minutes.
• Widely used, easy to perform but may
underestimate bullous lung disease

47. Nitrogen Washout
• Performed by having the patient breath
comfortably for several minutes and then
turn in to 100% O2 at FRC.
• Monitor N2 concentrations and test ends
when falls below 1%
• Easy to see leaks

48. Nitrogen Washout
• Concept is C1V1= C2V2
– C1 = Nitrogen concentration at the start of the
test
– V1 = FRC volume
– C2 =N2 concentration in exhaled volume
– V2 = Total exhaled volume during O2 breathing
period
– Nitrogen is measured by photoelectric principle

49. Body Plethsymography
• Is a sealed box with a fixed volume
• Uses Boyle’s Law that changes in pressure are
brought about by changes in volume for the
person seated in the box
• P1V1= P2V2

51. Body Plethysmograph

52. Interpretation
• RLD
– TLC is reduced in all
– Predicted values and
interpret same as FVC
and FEV1
• OLD
– TLC can be increased
and is then called
hyperinflation (120%)
– RV can be increased in
asthma and COPD
indicating air trapping

53. Diffusing Capacity
• Provides information about the transfer of gas
between the alveoli and the pulmonary
capillary bed
• It is the only noninvasive test of gas exchange
• Performed by a single breath technique and
uses CO as the inert gas

55. Diffusing Capacity
• Diffusion of a gas is dependent of the area,
the concentrations, the thickness of the
membrane and the diffusing properties of the
gas
• Diffusion is the rate at which a gas is
transferred across the alveolar capillary
membrane, the plasma, the RBC and
ultimately combined with Hgb

56. Diffusing Capacity
• CO is typically used because it is freely
diffusable
• It usually is not present in significant amounts
in the blood except in some heavy smokers
• Helium or methane is also used to measure
volume
• A single maximal inspiration is taken and held
for 10 sec

58. Diffusing Capacity
• Normal result is >80%
• Can be reduced in interstitial diseases such as
sarcoid or asbestosis
• Can be reduced also in emphysema or
pulmonary vascular diseases
• False low measurements in anemia or lung
resection

59. 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
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60. 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
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61. Predicted
Values
Measured
Values
% Predicted
FVC 6.00 liters 4.00 liters 67 %
FEV1 5.00 liters 2.00 liters 40 %
FEV1/FVC 38 % 50 % 60 %
Decision : This person is obstructed

62. Predicted
Values
Measured
Values
%
Predicted
FVC 5.68 liters 4.43 liters 78 %
FEV1 4.90 liters 3.52 liters 72 %
FEV1/FVC 84 % 79 % 94 %
Decision : This person is restricted

63. Decision: normal
Predicted
Values
Measured
Values
%
Predicted
FVC 5.04 liters 5.98 liters 119 %
FEV1 4.11 liters 4.58 liters 111 %
FEV1/FVC 82 % 77 % 94 %

64. Decision: mild restrictive lung disease
Predicted
Values
Measured
Values
%
Predicted
FVC 3.20 liters 2.48 liters 77 %
FEV1 2.51 liters 2.19 liters 87 %
FEV1/FVC 78 % 88 % 115 %

65. Decision: moderate obstruction
Predicted
Values
Measured
Values
%
Predicted
FVC 3.20 liters 3.01 liters 94 %
FEV1 2.51 liters 1.19 liters 47 %
FEV1/FVC 78 % 39 % 50 %

66. www.anaesthesia.co.in“Dr Helmi, may I be excused? My brain is full”