Respiratory Mechanics III

Question 1

What is obstructive pulmonary disease?

Answer 1

Characterized by high airway resistance

Emphysema, Asthma, Bronchitis, Cystic Fibrosis, COPD

Question 2

What is restrictive pulmonary disease?

Answer 2

Characterized by low lung compliance or increased stiffness of the lung and increased lung recoil

Pulmonary Fibrosis, Sarcoidosis, Silicosis, Asbestosis, Wegener’s Granulomatosis

Question 3

What is a relatively easy way to evaluate airway resistance?

Answer 3

FEV1 - should be 80%

Slope between 75% and 25% on the FEV1 graph (FEF 25-75%) is lower in patients with obstructive disease

Question 4

What is the FEV1/FVC ratio in obstructive and restrictive lung disease?

Answer 4

Obstructive - lower than 70%

Restrictive - normal to higher

*Important to consider in addition to other pulmonary factors

Question 5

What happens to the Flow-Volume loop in emphysema?

Answer 5

The loop shifts to the left towards larger volumes - due to high compliance of lung tissue

Smaller Expiratory flow rates - lower/scooping slope

RV much larger than normal

Question 6

What happens to the Flow-Volume loop in Restrictive lung disease?

Answer 6

Loop shifts to the right towards smaller volumes - due to low compliance

Graph is the same shape because there are no particular effects on the rates of inhalation or exhalation

Question 7

What does a reduced area on a Peak Expiratory Flow graph indicate?

Answer 7

Some ventilatory limitation, depending on shape, could be restrictive or obstructive

Question 8

What are variable obstructions?

Answer 8

Those in which the cross-sectional area of the obstruction is dependent on inspiratory or expiratory effort

Question 9

What is the effect of a variable intrathoracic legion on the flow volume loop?

Answer 9

Causes dynamic compression and therefore, has a significant effect on expiration rather than inspiration

Question 10

What is the effect of a variable extrathoracic legion on the flow volume loop?

Answer 10

Has a larger negative impact on inspiration rather than expiration

Question 11

What are fixed obstructions?

Answer 11

Obstructions that are not affected by inspiratory or expiratory effort

Caused by foreign bodies, or by scarring

Affect both forced inspiration and forced expiration

Question 12

What is the Methacholine Challenge test?

Answer 12

Used to detect hyperreactive airways by exposing the patient to increasing concentrations of methacholine

The test is considered positive when there is a 20% reduction in the FEV1

A PC20 of less than 8 mg/mL suggests clinically important airway hyperractivity