Respiratory measurements

Question 1

Name an obstructive airway disease

Answer 1

COPD

Question 2

Name a restrictive airway disease

Answer 2

Asthma

Question 3

What is the difference between a restrictive and obstructive airway disease

Answer 3

restrictive = limits amount of air getting to lungs
Obstructive = reduces ventilation capcity by reducing surface area for gas exchange

Question 4

What is lung compliance

Answer 4

strechibility/expandibility

Question 5

Describe the difference in lung compliance at low and high pressures

Answer 5

High = lung is stiffer, so compliance is lower
Low = lung more collapsed, compliance is higher

Question 6

Which is more compliant the base or apex of lung?

Answer 6

Base = better ventilation

Question 7

What is the reason for lung compliance?

Answer 7

elastic recoil

Question 8

What diseases when lung compliance is increased or decreased?

Answer 8

Decreased = pulmonary fibrosis, alveolar oedema
Increased = normal ageing lung

Question 9

For efficient ventilation, what do healthy people tend to have?

Answer 9

High lung compliance
Low alveolar surface tension due to surfactant secreted by alveoli

Question 10

What is pulmonary fibrosis?

Answer 10

Scarring of the lungs = reduces capacity of lung to perform function

Question 11

What do lung tests need to assess and what do they need to diagnose?

Answer 11

Mechanical condition of the lungs- pulmonary fibrosis
Resitance of the airways- asthma
Diffusion across the alveolar membrane- pulmonary fibrosis

Question 12

What is used to measure lung volumes?

Answer 12

spirometer

Question 13

Name 4 measurements of lung volumes

Answer 13

1. Tidal volume
2. Inspiratory reserve volume
3. Expiratory reserve volume
4. Vital capacity

Question 14

How does a spirometer work?

Answer 14

1. Must be closed system = clip on nose with mouth piece attached- told to breath in and out
2. Connected to apparatus that measures the movement
3. Everytime there is a movement, a needle moves on chart

Question 15

Define: Tidal volume

Answer 15

the amount of air that passes in and out of lungs during normal breathing

Question 16

Define: inspiratory reserve volume

Answer 16

= extra volume of air inspired above the normal tidal volume with full force

Question 17

Define: Expiratory tidal volume

Answer 17

extra volume of air expired by forceful expiration at the end of normal tidal expiration

Question 18

Define: vital capacity

Answer 18

maximum amount of air expelled from the lungs after first filling the lungs to a maximum then expiring to a maximum

Question 19

How do you work out the vital capacity?

Answer 19

Tidal volume + inspiratory reserve volume + expiratory reserve volume

Question 20

How do you work out the vital capacity?

Answer 20

Tidal volume + inspiratory reserve volume + expiratory reserve volume

Question 21

Name + define 3 measurements not using spirometry?

Answer 21

Residual volume = volume of air remaining in the lungs after the most forceful expiration

Functional residual capacity = amount of air that remains in the lungs at the end of normal expiration

Total lung capacity = maximum volume of air the lungs can hold

Question 22

What can be used to measure forced vital capacity?

Answer 22

Vitalograph

Question 23

What is the forced vital capacity?

Answer 23

= total volume of air that is exhaled

Question 24

What happens to air when we force a breath out?

Answer 24

90% of air will move out in 1st second- takes 3-5 seconds to complete forced exhalation

Question 25

What does FEV1 refer to?

Answer 25

= volume expired in the first second of a breath- typically above 70%

Question 26

what is used to determine the relationship between FEV1 and the FVC?

Answer 26

defined as a ratio- FEV1/FVC

Question 27

Apart from disease, what are the physiological/environmental factors affecting lung volumes?

Answer 27

Age
Height
Gender

Question 28

How do you measure functional residual capacity?

Answer 28

Using helium dilution or nitrogen washout

Question 29

Why are inert gases used in helium diluation or nitrogen washout?

Answer 29

They diffuse in and out of lung without any gas exchange

Question 30

Describe the process of nitrogen washout

Answer 30

Patient inspires 100% O2

Expires into the spirometer system

Procedure repeated until N2 in lungs is replaced with O2

FRC calculated from exhaled N2 and estimated alveolar N2