Pulmonary Function Testing 2023.pdf

Pulmonary Function Test
The Basics of Interpretation
Dr. Radhwan Hazem Alkhashab
Consultant anaesthesia & ICU
Assist prof.
2023
www.mosulitu.ahlamontada.net

Objectives of presentation
 Definition of PFT
 Identify the components of PFTs
 Describe the indications
 Develop a stepwise approach to interpretation.
 Evaluation of the patients for lung resection.

Definition
Measurement of a patient’s airflow (spirometry), lung
volumes, and diffusing capacity for inspired carbon
monoxide (DLCO).

Description
Spirometry
Flow Volume Loop
Bronchodilator response
Lung volumes
Diffusion capacity (DLCO)
Broncho provocation testing.

Indications — Diagnosis
Evaluation of signs and symptoms: SOB,
exertional dyspnea, chronic cough.
Screening at-risk populations
Abnormal study: CXR, ECG, ABG, hemoglobin
Preoperative assessment

Preoperative assessment
1. Patients with any evidence of chronic pulmonary disease
2. Heavy smokers with history of persistent cough
3. Patients with wheezing or dyspnea on exertion
4. Patients with chest wall and spinal deformities
5. Morbidly obese patients
6. Patients with thoracic surgery
7. Elderly patients (>70 years of age)
8 .Patients who are to undergo upper abdominal surgery

Indications — Prognostic
 Assess severity
 Follow response to therapy
 Determine further treatment goals
 Referral for surgery
 Disability.
(The 6min walk test is great to evaluate physical function and can be
used to assess therapeutic response in COPD patients. If oxygen sats
fall by >4% (ending below 93%), this indicates significant desaturation,
and need confirmatory ABGs.)

Contraindication
 Myocardial Infarction in the last month
 Unstable Angina.
 Recent thoracic and abdominal surgeries
 Recent Ophthalmic surgery
 Abdominal, thoracic and cerebral aneurysms.
 Active Hemoptysis.
 Pneumothorax.

Abbreviations in PFT
The functional residual capacity (FRC) is the volume in the
lungs at the end of passive expiration.
A normal FRC (1.7 to 3.5 L).
FRC is increased by:
 Body size (FRC increases with height).
 Age (FRC increases slightly with age).
 Certain lung diseases, including asthma and chronic
obstructive pulmonary disease (COPD).

FRC is decreased by:
 Sex (woman have a 10% decrease in FRC when
compared to men).
 Diaphragmatic muscle tone (individuals with paralyzed
diaphragms have less FRC when compared to normal
individuals).
 Posture (FRC greatest standing > sitting > prone >
lateral > supine).
 Certain lung diseases in which elastic recoil is
diminished (e.g., interstitial lung disease,kyphoscoliosis).
 Increased abdominal pressure (e.g., obesity, ascites

Forced expiratory
volume in 1
second (FEV1)
The maximum volume of
air that can be expired in
the first second of forced
expiration after
maximum inspiration
≥ 80% of the predicted
average value,
Or > 75% of vital
capacity
Forced expiratory flow
rate at 75%, 50%, and 2
5% of vital capacity
(FEF75%, FEF50%, FEF25
%)
Average airflow rates
observed during forced
expiration when 75%,
50% , and 25%
average value
FVC: force vital capacity
The amount of air that
can be forcibly exhaled
from your lungs after
taking the deepest
breath possible
3-4 L
FEV1/FVC ratio Ratio of FEV1 to FVC •≥ 0.7
Peak expiratory
flow (PEF)
The maximum airflow
rate attained during
forced expiration
(L/second)
average value

How The Test Is Performed
 The predicted PFT values are vary according to age,
height, gender, and ethnicity.
 In a spirometry test, you breath into a mouthpiece that is
connected to an instrument called a spirometer. The
spirometer records the amount and the rate of air that
you breath in and out over a period of time.
 For some of the test measurements, you can breath
normally and quietly. Other tests require forced
inhalation or exhalation after a deep breath.

Lung volume measurement can be done
by Body plethysmography
Plethysmography is the gold standard test for
measuring lung volumes and, unlike spirometry, it can also
measure TLC and RV.
The most accurate way is to sit in a sealed, clear box that
looks like a telephone booth (body plethysmograph) while
breathing in and out into a mouthpiece. Changes in
pressure inside the box help determine the lung volume.

Indications of Body plethysmography
Patients who cannot actively participate in spirometry:
1.Obstructive lung disease on spirometry: to evaluate
for air trapping (e.g., in emphysema).
2.Restrictive lung disease: to distinguish between extrinsic
vs. intrinsic causes.

Parameters of body plethysmography
Includes spirometry parameters plus:
1.Airway resistance (Raw): the resistance to airflow from the
mouth to the alveoli during inspiration and expiration.
2.Residual volume (RV).
3.Total lung capacity (TLC).
4.Lung compliance (measured using an esophageal probe).

Spirometry
 Simple, office-based
 Can determine:
- Forced expiratory volume in one second (FEV1)
- Forced vital capacity (FVC)
- FEV1/FVC
- Forced expiratory flow 25%-75% (FEF25-75)

VC & FVC
 FVC tends to be less than the standard VC because
airways reach flow limitation early, and air trapping
occurs. In healthy subjects, the two maneuvers usually
result in nearly equal measured volumes. Because the
FVC maneuver is an artificial one, patients must be
instructed carefully and often require practice attempts
before performing the test adequately.

Note :-
The exhalation should take at least 4 seconds and should
not be interrupted by coughing, glottic closure, or any
mechanical obstruction.

 The FEV1 provides an even better perspective on the
degree of airway obstruction when it is expressed as a
percentage of the FVC (FEV1 /FVC%).
 Normal healthy subjects can exhale 75 to 80 percent of
the FVC in the first second; the remaining volume is
exhaled in two or three additional seconds

Clinical ranges for FEV1 in liters
Clinical ranges Patients group

Obstructive Pattern
Obstructive airway diseases, including asthma, chronic
bronchitis, emphysema, cystic fibrosis, and bronchiolitis,
exhibit diminished expiratory airflow and involve airways
distal to the carina. The FEV1, FEV1/FVC ratio, and the
forced expiratory flow at 25% to 75% of FVC (FEF25-75)
are below predicted values. A decreased FEF25-75 reflects
collapse of the small airways and is a sensitive indicator of
early airway obstruction.

Restrictive lung disorders
Impaired ability of the lungs to expand (as a result of reduced lung
compliance).Includes
 Intrensic causes:
1.Interstitial lung diseases: sarcoidosis, ARDS, pulmonary fibrosis.
2.Alveolar (e.g., pneumonia, pulmonary edema, hemorrhage).
 Extrinsic causes : (i.e., extrapulmonary conditions that change the
mechanics of respiration)
Diseases of the pleura and pleural cavity(e.g., chronic pleural
effusion, pneumothorax
Deformities of the thorax / mechanical limitation
; (e.g., kyphoscoliosis, ankylosing spondylitis , obesity ,
ascites, pregnancy.

The decreased VC associated with restrictive disease may
result from lung pathology, such as pneumonia, atelectasis,
and pulmonary fibrosis. It may also occur with a loss of
distensible lung tissue, such as that following surgical
excision. Decreased VC is also seen in the absence of lung
disease. In this case, muscle weakness, abdominal
swelling, or pain may prevent the patient from obtaining
either a full inspiration or a maximum expiratory effort.

Abnormal PFT in RLD
 Decreased FEV1
 Decreased FVC
 FEV1/FVC normal or increased

Bronchodilator Response
 Degree to which FEV1 improves with inhaled
bronchodilator
 Documents reversible airflow obstruction
 Significant response if:
- FEV1 increases by 12% and >200ml
 Request if obstructive pattern on spirometry
 Note : patient should hold MDI the morning prior to test.

The response to bronchodilators is expressed as the
percentage change in FEV1 from a baseline value. Healthy
normal subjects and those with very mild obstruction
typically exhibit a minimal increase in FEV1 (<5%).
Likewise, patients with severe baseline obstruction respond
poorly because of accompanying secretions and airway
edema. The most dramatic improvement occurs in patients
with moderate obstruction such that response to
bronchodilators

Flow Volume Loop
Flow-volume loops assist in
identifying the anatomic
location of airway obstruction.
Forced expiratory and
inspiratory flow at 50% of FVC
(FEF50 and FIF50). Note that
expiratory flow is represented
above the x-axis, whereas
inspiratory flow is represented
below the axis. In a normal
flow-volume loop the
FEF50/FIF50 ratio is 1.

Abnormal Flow-Volume Loops
The finding of reduced peak flow
and FEV1 without additional
clinical evidence of chronic
obstructive lung disease may
indicate the presence of an
obstructing lesion of the upper
airway, larynx, or trachea. In
some cases, this obstruction
may be suspected by a careful
history and physical
examination.

Lung Volumes
Indications:
- Diagnose restrictive component
- Differentiate chronic bronchitis from
emphysema.
FVC is decreased in both obstructive and restrictive
disease, so usually need to obtain lung volumes to see if
restrictive component present (increased TLC).

Lung Volumes – Patterns
 Obstructive
- TLC > 120% predicted
- RV > 120% predicted
 Restrictive
- TLC < 80% predicted
- RV < 80% predicted

Diffusing Capacity
• The DLCO Measure of gas exchange at alveolar-capillary
membrane.
• Changes in DLCO are one of the earliest signs of
interstitial lung disease (ILD).
The DLCO measures the rate of uptake of the non
physiologic gas carbon monoxide (CO). CO is used because
of its affinity for hemoglobin and because it reflects the
diffusing capacity of the physiologic gases oxygen and
carbon dioxide. DLCO is dependent on membrane-diffusing
capacity and the pulmonary vasculature and thus is a
measure of functioning alveolar capillary units. This test has
been used as an indicator of suitability for pulmonary
resection and a predictor of postoperative pulmonary
morbidity.

Diffusing Capacity
 Decreased DLCO
(<80% predicted)
 Obstructive lung disease
 Parenchymal disease
 Pulmonary vascular disease
 Anemia.
Low DLCO is also a major
predictor of desaturation during
exercise.
 Increased DLCO
(>120-140% predicted)
 Asthma
 Polycythemia
 Left to right shunt
 Congestive heart failure

DLCO — Indications
 Differentiate asthma from emphysema
 Evaluation and severity of restrictive lung disease
 Early stages of pulmonary hypertension

Bronchoprovocation
Useful for diagnosis of asthma in the setting of normal
pulmonary function tests
 Common agents:
- Methacholine, Histamine, others
 Diagnostic if: ≥20% decrease in FEV1

Continued…
↓
SYMPTOMS
PFTs
OBSTRUCTION?
YES NO
TREAT
BRONCHOPROVOCATION
Obstruction?
TREAT
No Obstruction?
Other Diagnosis
↓
↓
↓ ↓
↓
↓ ↓

Obstructive Pattern — Evaluation
Spirometry
 FEV1, FVC: decreased
 FEV1/FVC: decreased (<70% predicted)
FV Loop “scooped”
Lung Volumes
 TLC, RV: increased
 Bronchodilator responsiveness
 Don’t need a DLCO, but if were decreased would make you think
emphysema, if normal then chronic bronchitis.

Restrictive Pattern – Evaluation
Spirometry
 FVC, FEV1: decreased
 FEV1/FVC: normal or increased
FV Loop: “witch’s hat”
DLCO decreased
Lung Volumes
 TLC, RV: decreased
• IF restrictive pattern, you’re going to want to get DLCO b/c it tells
you whether the restriction is due to parenchymal disease or NM,
pleural or CW disease

PFT Patterns
Emphysema
 FEV1/FVC <70%
 “Scooped” FV curve
 TLC increased
 Increased compliance
 DLCO decreased
Chronic Bronchitis
 FEV1/FVC <70%
 “Scooped” FV curve
 TLC normal
 Normal compliance
 DLCO usually normal.
why/?

PFT Patterns
Asthma:
 FEV1/FVC normal or decreased
 DLCO normal or increased
But PFTs may be normal  bronchoprovocation

Preoperative evaluation for lung resection
Resection of lung disease results in a greater impairment in
postoperative lung function .
Lung resection in patients with pulmonary dysfunction is
associated with a high risk of postoperative complications,
even the possibility of death. These patients require a more
extensive pulmonary evaluation, particularly if removal of
an entire lung is anticipated.

The long-term ability to withstand such lung resection
relates to the amount and the functional status of the lung
parenchyma removed and more importantly to the function
of the remaining lung tissue. Removal of lung from an
already compromised patient may be followed by
inadequate gas exchange, pulmonary hypertension, and
incapacitating dyspnea.

The pulmonary function studies must be viewed in light of
the patient's age, the status of the cardiovascular system,
and the patient's cooperation and motivation. Data in
pneumonectomy patients indicate that whole lung removal
is likely to be tolerated if the preoperative pulmonary
function meets the following criteria :
1. FEV1 greater than 2 L.
2. FEV1 /FVC ratio of at least 50 percent.

V/P scan
If any of these criteria are not met, more sophisticated
testing of split lung function is indicated in order to estimate
the relative functional contribution of each lung. Usually,
split function testing consists of xenon radiospirometry to
assess ventilation and macroaggregates of iodine or
technetium to scan perfusion. The relative contribution of
each lung to either total ventilation or perfusion can be
used to predict postoperative pulmonary function.

• It appears that resting pulmonary function testing does
not accurately predict exercise performance in patients
with more severe lung disease.
• Thus, cardiopulmonary exercise testing may be
necessary to evaluate the degree of impairment.
Exercise testing has become attractive because it
reflects gas exchange, ventilation, tissue oxygenation,
and cardiac output. When COP is increased, blood flow
to the pulmonary vascular bed increases, much like
occurs when flow is diverted to the lung tissue remaining
after resection.

Note :
No single PFT result absolutely contraindicates surgery.
Factors such as physical examination, arterial blood gases,
and coexisting medical problems also must be considered
in determining suitability for surgery.

Pulmonary Function Testing 2023.pdf

Pulmonary Function Testing 2023.pdf

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