6. Spirometry

Question 1

Describe the 2 types of vital capacity deficit seen in spirometry

Answer 1

1. RESTRICTIVE
   - decreased max. filling of lungs due to decreased lung expansion (e.g. decreased compliance) causing decreased lung volume, increased work of breathing and inadequate ventilation
2. OBSTRUCTIVE
   - decreased max. emptying of lungs due to airway narrowing causing compromised expiratory flow

Question 2

name examples of obstructive and restrictive resp. diseases

Answer 2

1. OBSTRUCTIVE: COPD, asthma, bronchiectasis

2. RESTRICTIVE: fibrosis, NRDS, pneumonia

Question 3

what are FVC and FEV1 and how are these measured

Answer 3

• FVC (forced vital capacity) = volume of air breathed out from maximal effort expiration
• FEV1 = volume of air exhaled after 1sec forced expiration

Measured using time-flow curve.

Question 4

what is the normal FEV1/FVC

Answer 4

> 70%

Question 5

describe the changes in FVC, FEV1 and FEV1/FVC ratio in obstructive and restrictive deficits

Answer 5

Obstructive:

• sig. reduced FEV1
• sig. reduced FEV1/FVC (<70%)
• near normal FVC

Restrictive:

• sig. reduced FVC
• proportionally reduced FEV1
• normal FEV1/FVC

Question 6

what do flow-volume loops measure

Answer 6

Peak expiratory flow rate - plots flow (L/sec) against volume expired

Question 7

describe the changes seen in obstructive and restrictive deficits in flow-volume loops

Answer 7

Obstructive:

• decreased PEFR
• scalloping of curve

Restrictive:
- decreased lung volume die to decreased inspiratory volume