Clinical evaluation of respiratory function

Question 1

What is Spirometry?

Answer 1

Method of quantifying vital capacity, airflow, and the level of airway obstruction present during breathing.
Spirometry is used to measure airway function.

Question 2

What does spirometry involve?

Answer 2

Involves the patient producing a maximum forced expiration into a spirometer, which measures the volume of air passing through over time. This can then be plotted on a graph

Question 3

What does a spirometry trace deomstrate?

Answer 3

FVC - Forced Vital Capacity

FEV1 - Forced Expiratory Volume in 1 second

Question 4

What is FEV1?

Answer 4

Forced expiratory volume in 1 second.
It is the maximum volume that can be expired during the first second of a maximum forced expiration.
Reflects airway function and health

Question 5

What is FVC?

Answer 5

Maximum volume an individual can exhale in one breath after inspiring as much air as possible.
Reflects the volume of the lungs that the individual can utilise when breathing.

Question 6

How are FEV1 values normally expressed?

Answer 6

As FEV1/FVC ratio to take in to account that different individuals have varying rates of healthy airflow depending on their vital capacity.
E.g. larger lungs and airways will always naturally expire air faster.

Question 7

What can spirometry be used for?

Answer 7

To identify and differentiate between obstructive and restrictive respiratory disease (and quantify disease severity).

Question 8

FEV1/FVC for obstructive respiratory disease

Answer 8

FEV1/FVC <70%

FVC = Normal

Question 9

FEV1/FVC for Restrictive respiratory disease

Answer 9

FEV1/FVC = Normal

FVC <80% of predicted volume

Question 10

FEV1/FVC for Mixed Obstructive and Restrictive respiratory disease

Answer 10

FEV1/FVC <70% and FVC<80%

Question 11

Examples of obstructive airway disease

Answer 11

Asthma

Chronic bronchitis

Question 12

Examples of Restrictive respiratory diseases

Answer 12

Pulmonary fibrosis

Question 13

Examples of mixed Obstructive and Restrictive respiratory diseases

Answer 13

COPD

Question 14

What are pressure-volume loops used for?

Answer 14

Used to quantify dynamic lung compliance, as well as potential airway obstruction.
Greater V/P gradient the greater the compliance.
Greater the area of the loop the greater the airway obstruction

Question 15

What are arterial blood gas readings used for?

Answer 15

Can be used to identify acid-base disorders and when compensation is occurring

Question 16

What is the Alveolar Gas Equation used for?

Answer 16

Used to interpret arterial blood gas readings and determine if hypoventilation and/or blood oxygenation are contributing to hypoxaemia.
Excessive PaCO2 = hypoventilation
Excessive A-a (>2kPa) = impaired oxygenation

Question 17

Causes for acidosis

Answer 17

CO2 is high = Respiratory acidosis

HCO3- is low = Metabolic acidosis

Question 18

Causes for alkalosis

Answer 18

CO2 is low = Respiratory alkalosis

HCO3- is high = Metabolic alkalosis