Pulmonary Function Tests
J.B. Handler, M.D.
Physician Assistant Program
University of New England
1
Abbreviations









ARDS- adult respiratory
distress syndrome
DLCO- diffusion capacity for
carbon monoxide
Ht- height
Wt- weight
SOB- short of breath
Pred- predicted
Meas- measured
PFT- pulmonary function test
ABG- arterial blood gas
2
PFT’s: Indications

Detect abnormalities and severity of lung function
in presence of disease.
– Monitor course of disease.




Baseline pulmonary function prior to surgical,
medical or radiation therapy.
Differentiation of obstructive vs restrictive
disease.
Evaluate response to therapy, reversibility.
Determine the preoperative risk of thoracic
surgery.
3
Lung Volumes
Images.google.com
Lung Volumes

IC

Images.google.com
Tidal Volume (TV):
amount of air inhaled
and exhaled at rest;
normal= 500-750 ml.
Inspiratory Capacity
(IC): beginning of
normal inhalation to
maximum inspiration.
Lung Volumes


Images.google.com
Inpiratory Reserve
Volume (IRV): Volume
measured from “top” of
the TV (point of normal
exhalation) to maximum
inspiration.
Expiratory Reserve
Volume (ERV): Volume
measured from the
“bottom” of the TV (point
of normal inhalation) to
maximum expiration.
Lung Volumes


Images.google.com
Residual Volume (RV):
The amount of air left in
the lungs following full
exhalation to the ERV..
Functional Residual
Capacity (FRC) = ERV +
RV: amount of gas
remaining in the lungs at
the end of the tidal
volume.
Lung Volumes


Images.google.com
Vital Capacity (VC):
volume of air
measured from full
inhalation to
maximum exhalation
Total Lung Capacity
(TLC): summation of
the RV + vital
capacity.
Spirometer
Spirometry


Forced Vital Capacity (FVC)- Following full
inspiration, patient exhales as rapidly as possible,
forcibly and completely- volume of air exhaled is
measured; takes 5-6 seconds with majority in 1
second. Wide range of normal (see below).
Volume obtained is expressed as a % of predicted
normal. Normals are based on volumes obtained
from thousands of healthy individuals of similar
age, sex, ht and wt and race. Normal 80% of
predicted.
10
Spirometry


FEV1 :Amount of air forcibly exhaled in the 1st
second of the FVC maneuver (80% of FVC
volume). Normal 80% predicted; wide range of
normal (see below).
Volume obtained is expressed as a % of predicted
normal. Normals are based on volumes obtained
from thousands of healthy individuals of similar
age, sex, ht and wt and race. Normal  80% of
predicted.
11
Spirometry



FEV1/FVC: Very important ratio; when reduced,
helps identify presence of obstructive disease.
Percentage reduction correlates with severity of
obstruction; normal is 75-80+%. Normal (or )
in patients with restrictive disease.
Obstructive airway disease: Asthma, COPD.
Restrictive disease: Interstitial lung disease,
kyphoscoliosis, pleural disease & others).
12
Peak Expiratory Flow Rate





Measured using simple hand held device.
Occurs within the first milliseconds of forced
expiration and is a measure of maximum airflow
rate.
Wide variation in normal ranges (age, ht and sex)
adult males: 400-700L/minute.
adult females: 300-600L/minute.
Effort dependent.
When abnormal- indicator of large airways
obstruction.
13
Peak Expiratory Flow Rate
Clinical use: Assessment of patients with
asthma.
 Patient determines “personal best” PEFR
when most healthy, between asthma attacks.
 PEFR often precedes symptoms.
 Guide for responsiveness to meds,
worsening of episodes, when to get help,
etc.

14
Diffusion Capacity





Tests gas exchange across the alveolar-capillary
membrane.
Per minute transfer of gas- Carbon Monoxide
measured from alveoli to blood; DLCO.
Decreased if thickened alveolar capillary
membrane (pulmonary fibrosis, ARDS), or
following loss of surface area of the alveoli.
Most useful and decreased in interstitial lung
disease (lecture to follow).
Normal mean is 25-30 mL/min/mmHg.
15
Application of PFT’s
Obstructive disease: asthma, COPD,
bronchiectasis.
 Pattern: FVC normal or decreased mildly.
FEV1 decreased; reduction reflects
severity.
 FEV1/FVC decreased- reflects severity.
 Response to bronchodilator indicates
reversible component.

16
Application of PFT’s
Restrictive disease: pulmonary fibrosis,
sarcoidosis, kyphoscoliosis, neuromuscular
disease, others.
 Pattern: FVC decreased, often markedly.
FEV1 decreased, often markedly.
 FEV1/FVC normal or increased.
 No response to bronchodilator.

17
Problem Solving
22 y.o male with cough, SOB, and wheezing.
 FVC – 3.63L (pred), 3.23L (meas), 89% pred
 FEV1- 3.24L (pred), 2.24L (meas), 69% pred
 FEV1/FVC 69% (meas)
Post bronchodilator:
 FVC- 3.23L
 FEV1- 2.70L (meas) 83% pred
 FEV1/FVC 84% (meas)
 Interpretation: mild obstructive airways disease with post
bronchodilator reversibility.
 Diagnosis: Asthma
18
Problem Solving







45 y.o black man with progressive shortness of
breath.
FVC- 3.05L (pred), 0.81L (meas), 22% predicted
FEV1- 2.9L (pred) 0.69L (meas), 24% predicted
FEV1/FVC 97% (meas)
No change post bronchodilator
Interpretation: Severe restrictive disease; no
evidence of airway obstruction.
Diagnosis: Sarcoidosis
19
Pulse Oximetry
Measures per cent oxygenation of
hemoglobin (oxyhemoglobin).
 Non-invasive; measures absorption of light
passing through tissue, then calculates O2
saturation of arterial blood.
 Measured via electrodes placed on skinfingertips, ear lobes.
 Normal = 97%

20
Arterial Blood Gas Measurement





Requires arterial puncture
pH of arterial blood
PO2: partial pressure of oxygen (mmHg)
PCO2: partial pressure of carbon dioxide (mmHg)
HCO3: calculated- bicarbonate; proportional to
dissolved CO2 in blood.
21
O2-Hemoglobin Dissociation
Images.google.com