Activity 1 - Tidal volume and ventilation in quiet breathing

In this activity, we will explore the respiratory cycle and measure changes in flow and volume.

The spirometer trace shown below was obtained when the subject was breathing quietly for several minutes and then performed a vital capacity manoeuvre by taking the biggest breath in and then breathing out as much as possible.

Interpreting the spirometer traces

On the volume traces in the following activities, an upwards deflection indicates inspiratory volume (breathing in), whilst a downwards deflection indicates expiratory volume (breathing out).


  • Press Start to begin quiet breathing.
  • After a few moments, press Perform VCM to simulate a vital capacity manoeuvre.
  • Use the trace and reference marker to answer the questions below.

Note: The simulation runs at × normal speed

Timer: 0:00.00

Use the spirometer trace to estimate the tidal volume, vital capacity, the breathing frequency and the minute ventilation.