How can breathing be measured? Take a moment to write a list of variables relevant to breathing.

Respiration rate (number of breaths per unit time), lung capacity, depth of respiration, and rate of airflow are all ways to measure breathing.

A spirometer measures the rate of flow of air from breathing. Consider the graphs of spirometer readings below, excerpted from a book series by Schottenbauer Publishing.

__Discussion Questions__

- In each graph above, what are the maximum and minimum flow rates?
- In each graph above, what is the period of breath cycle?
- In each graph above, what is the frequency of breath cycle?
- Why is the first graph not a perfect sine wave?
- Why is the second graph not showing the same shape as the first graph?

**Additional Information**