Interpretation of Pulmonary Function Tests

Question 1

What is tidal volume?

Answer 1

• Volume of air inspired and expired with each normal breath

Question 2

What is forced vital capacity (FVC)?

Answer 2

• Amount of air that can be forcefully expelled beginning with the lungs completely full and blowing maximally until the lungs are as empty as possible

Question 3

What is forced expiratory volume in first second (FEV1)?

Answer 3

• Amount of air expelled during the first second of the FVC maneuver

Question 4

What is the residual volume?

Answer 4

• Volume of air remaining in lungs after most forceful expiration

Question 5

What is the total lung capacity?

Answer 5

• Maximum volume to which the lungs can be expanded with inspiration

Question 6

What does the spirometry with flow volume curves or loops measure?

Answer 6

• FVC
• FEV1
• FEV1/FVC ratio

Question 7

What does the FEV1/FVC ratio tell?

Answer 7

• Restrictive vs obstructive lung disease

Question 8

What measures lung volumes and capacities?

Answer 8

• Most commonly plethysmography

- Looks at TLC and RV

Question 9

What is the DLCO?

Answer 9

• Test to measure the gas exchange through alveolar wall

Question 10

How is a DLCO test done?

Answer 10

• Patient inhales a small amount of CO for 10 seconds then exhales quickly
• The concentration of CO is measured and the DLCO is calculated

Question 11

What is bronchodilator therapy?

Answer 11

• Used only in obstructive lung disease to determine if airway obstruction is reversible

Question 12

What is a positive bronchodilator therapy?

Answer 12

• If there is a >12% increase in FEV1 or FVC and an absolute volume increase of >200ml
• Positive means asthma

Question 13

What happens if the bronchodilator test is negative but asthma is still suspeced?

Answer 13

• Use a bronchoprovocation, specifically, give methacholine to close up airways

Question 14

What is a positive methacholine challenge?

Answer 14

• If there is a >20% reduction in FEV1 at or before administration of inhaled methacholine

Question 15

What does obstruction lung disease look like on flow volume curves?

Answer 15

• Concave or scooping pattern

Question 16

What does restrictive lung disease look like on flow volume curves?

Answer 16

• Peaked, steeple, or witch’s hat pattern

Question 17

What are some causes of obstructive lung disease?

Answer 17

• COPD
• Asthma
• Bronchiectasis
• Bronchiolitis

Question 18

What are some causes of restrictive lung disease?

Answer 18

• Abnormalities of chest wall or pleura
• Drugs
• Interstitial lung disease
• Neuromuscular disease

Question 19

What are the spirometry results of obstructive lund disease?

Answer 19

• FEV1 <80% predicted
• FVC can be normal or reduced
• FEV1/FVC is <0.70
• Flow volume curve with scooped or concave pattern

Question 20

What are the lung volumes and capacities of obstructive lund disease?

Answer 20

• Increased total lung capacity due to air trapping

- Increased residual volume from air trapping

Question 21

What are the DLCO results of obstructive lung disease?

Answer 21

• Could be normal or low
• In emphysema, DLCO will be low
• In asthma or bronchitis, DLCO will be normal

Question 22

What are the spirometry results for restrictive lung disease?

Answer 22

• FEV1 is normal or mildly reduced
• FVC <80% predicted
• FEV1/FVC ratio is >0.70
• Flow volume curve is peaked, steeple, or witch’s hat pattern

Question 23

What are the lung volumes and capacities of restrictive lund disease?

Answer 23

• Decreased total lung capacity

- Decreased residual volume

Question 24

What are the DLCO results in restrictive lungdisease?

Answer 24

• Could be low or normal
• In ILD, tends to be low
• In neuromuscular or chest wall abnormalities, tends to be normal

Question 25

What shows a mixed PFT?

Answer 25

• If the FEV1/FVC ratio is low and the TLC is low <5 percentile of predicted