5.7.9 – How to investigate the effects of exercise on tidal volume and breathing rate

A spirometer is used to plot breathing patterns


Vital Capacity: The maximum amount of air a person can exhale   after inhaling the maximum possible volume of air

Tidal Volume: The volume of air inhaled & exhaled in one breath

Basal Metabolic Rate: The rate of respiration

The spirometer can be used to plot VC and TV directly. BMR can be worked out if a CO2 scrubber is used. The spirometer has fixed volume and is filled with 100% O2 before the experiment begins. As the person respires, O2 is replaced proportionally with CO2. The total volume should stay constant. However, if CO2 is removed, the total volume will slowly fall as O2 is used. The rate at which the volume decreases is proportionaly to BMR.

You are not expected to know how the spirometer works… although its not very difficult to understand.