Spirometry (CP 17)

Question 1

State what tidal volume is, its units, and, using a spirometer graph, show how it is calculated

Answer 1

Tidal volume is the volume of air that is exhaled or inhaled with each respiratory cycle. Usually measured in ml or dm^3 it is calculated by finding how much air is inhaled or exhaled from one breath.

Question 2

State what breathing rate is, its units, and, using a spirometer graph, how it is calculated

Answer 2

This is the number of breaths per minute and is found by counting the number of breaths (individual tidal volumes) that can be seen on the spirometer in a minute

Question 3

State what minute volume is, its units, and, using a spirometer, show how it is calculated

Answer 3

This is the volume of gas exhaled or inhaled from the lungs within a minute. To calculate this multiply the tidal volume and breathing rate values calculated from the spirometer trace

Question 4

State what oxygen consumption is, its units, and using a spirometer graph, how to calculated

Answer 4

The volume of oxygen inhaled and used by the body within a minute. Measured in ml or dm^3 a minute or second.

To calculate this find the volume of oxygen inhaled divided by the time period it occurs in.

Question 5

A person has a breathing rate of 5 breaths in 30 seconds and a tidal volume of 0.6dm3. Calculate the minute ventilation of this person

Answer 5

Minute ventilation = 10 x 0.6dm3
= 60dm3/min

Question 6

A person uses 1.2dm3 of oxygen over 3 minutes. Calculate their oxygen consumption

Answer 6

Oxygen consumption = volume of O2 consumed / time

1.2dm3 / 3 minutes =0.4 dm³/minute