Pulmonary Function Tests - An Introduction

Question 1

Purpose of pulmonary function tests

Answer 1

Diagnosis of symptomatic disease
Screening for early, asymptomatic disease
Prognostication of known disease
Monitor response to treatment
Help classify diffuse lung disease into - obstructive, restrictive or pulmonary

Question 2

Functions of the pulmonary system tested by PFTs

Answer 2

Provide information of every component of respiration
Latency of airways
Parenchyma
Pulmonary vasculature
Bellows/pump mechanism
Neural control of ventilation

Question 3

Standard PFTs

Answer 3

Spirometry
Lung volumes
Diffusing capacity of carbon monoxide

Question 4

Specialized PFTs

Answer 4

Arterial blood gas
Exercise oximetry
6 minute walk test
Peak flow
Maximum inspiratory and expiratory pressure

Question 5

What is spirometry used for?

Answer 5

Measuring airflow and some lung volumes

Question 6

Major values measured by spirometry

Answer 6

FEV1
FVC
FEV1/FVC ratio
Flow volume loop

Question 7

Minor values measured by spirometry

Answer 7

Peak expiratory flow rate (PEFR)
FEF 25-75%
Maximal voluntary ventilation (MVV)
Response to bronchodilators

Question 8

What does the FEV1/FVC ratio distinguish?

Answer 8

Obstructive from restrictive lung disease

Question 9

What is diffusing capacity of carbon monoxide (DLCO) a measure of?

Answer 9

How much volume of carbon monoxide diffuses per minute per unit of pressure across the alveolar capillary membrane

Question 10

What will decrease DCLO?

Answer 10

Anything that decreases membrane surface area
Anything that increases membrane thickness
Pulmonary hypertension of any cause
Anemia

Question 11

What will increase DLCO?

Answer 11

Exercise immediately prior to the test increases cardiac output
Supine position change
Asthma
Pulmonary hemorrhage
Polycythemia
Mild left heart failure
Obesity - occasionally

Question 12

What is the greatest diagnostic benefit for DLCO?

Answer 12

Differentiating the etiologies of restrictive lung disease

Question 13

Primary indications for measuring DLCO?

Answer 13

To categorize patient with restrictive lung disease as either probable ILD vs extra thoracic restriction
Identify early ILD in high-risk patients
To quantify anatomic emphysema in patients with COPD
To document disability for legal purposes

Question 14

ABCDEFG

Answer 14

Assessment
Bone
Cardiac silhouette and side
Diaphragms
Equipment
Lung fields
Great vessels

Question 15

Assessment

Answer 15

Assess patient and exam data
Assess image quality

Question 16

Bone

Answer 16

Body wall - soft tissue outside chest, checked for swelling or massess

Question 17

Cardiac silhouette and size

Answer 17

Right strum, atrial appendage, left ventricle
Measuring across a normal heart is < 50% of the greatest diameter of the rib cage measured from the inner portion of each rib - any large could indicate cardiac pathology

Question 18

Diaphragms

Answer 18

Shouldn’t be too flat but appear fairly symmetric

Question 19

Equipment

Answer 19

Lines, tubes, wires - note where they’re located
Functional position

Question 20

Lung fields

Answer 20

Should look symmetric
No haziness, white dots or blotches
Frontal and lateral X-ray allow us to determine in which lobe and lung an abnormality is located

Question 21

Great vessels

Answer 21

Superior and inferior vena cava
Ascending and descending aorta
Aortic arch - should be highest up (L side of heart), followed by the pulmonary artery
Pulmonary artery