### Introduction

Oxygen plays a key role in aerobic cellular metabolism, facilitating the conversion of glucose, protein, and lipids into usable energy. For every 6 molecules of oxygen used in the breakdown of glucose, 6 molecules of carbon dioxide are produced, along with water and adenosine triphosphate (ATP), according to the following equation:

${{\text{C}}_{\text{6}}}{{\text{H}}_{{\text{12}}}}{{\text{O}}_{\text{6}}}{\text{ + 6 }}{{\text{O}}_{\text{2}}} \to {\text{6 C}}{{\text{O}}_{\text{2}}}{\text{ + 6 }}{{\text{H}}_{\text{2}}}{\text{O + energy (heat or ATP)}}$

The average person uses 200–250 mL of O2 per minute at rest. This may increase to 2–3 L per minute during heavy exercise and to twice that amount in highly trained athletes. The increase of oxygen consumption is proportional to the amount of work performed up to a maximum level which is dependent on conditioning. At the start of exercise, anaerobic metabolism is used briefly, but this quickly changes to aerobic metabolism as blood flow to muscles increases.

### Objectives

In this experiment, you will

• Obtain graphical representation of tidal volume and change in O2 concentration with breathing at rest and after exercise.
• Calculate oxygen consumption at rest and after exercise.
• Correlate your findings with clinical situations.