Pulmonary Function Tests - An Introduction Flashcards
Purpose of pulmonary function tests
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
Functions of the pulmonary system tested by PFTs
Provide information of every component of respiration
Latency of airways
Parenchyma
Pulmonary vasculature
Bellows/pump mechanism
Neural control of ventilation
Standard PFTs
Spirometry
Lung volumes
Diffusing capacity of carbon monoxide
Specialized PFTs
Arterial blood gas
Exercise oximetry
6 minute walk test
Peak flow
Maximum inspiratory and expiratory pressure
What is spirometry used for?
Measuring airflow and some lung volumes
Major values measured by spirometry
FEV1
FVC
FEV1/FVC ratio
Flow volume loop
Minor values measured by spirometry
Peak expiratory flow rate (PEFR)
FEF 25-75%
Maximal voluntary ventilation (MVV)
Response to bronchodilators
What does the FEV1/FVC ratio distinguish?
Obstructive from restrictive lung disease
What is diffusing capacity of carbon monoxide (DLCO) a measure of?
How much volume of carbon monoxide diffuses per minute per unit of pressure across the alveolar capillary membrane
What will decrease DCLO?
Anything that decreases membrane surface area
Anything that increases membrane thickness
Pulmonary hypertension of any cause
Anemia
What will increase DLCO?
Exercise immediately prior to the test increases cardiac output
Supine position change
Asthma
Pulmonary hemorrhage
Polycythemia
Mild left heart failure
Obesity - occasionally
What is the greatest diagnostic benefit for DLCO?
Differentiating the etiologies of restrictive lung disease
Primary indications for measuring DLCO?
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
ABCDEFG
Assessment
Bone
Cardiac silhouette and side
Diaphragms
Equipment
Lung fields
Great vessels
Assessment
Assess patient and exam data
Assess image quality
Bone
Body wall - soft tissue outside chest, checked for swelling or massess
Cardiac silhouette and size
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
Diaphragms
Shouldn’t be too flat but appear fairly symmetric
Equipment
Lines, tubes, wires - note where they’re located
Functional position
Lung fields
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
Great vessels
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
