In the resting adult, what percentage of total body O2 consumption is due to the work of breathing?

In the resting adult, what percentage of total body O2 consumption is due to the work of breathing?

• A. 2%
• B. 5%
• C. 10%
• D. 20%

Answer: (A)

The amount of oxygen the body uses to power the act of breathing at rest is a small portion of total oxygen consumption. In a healthy resting adult, the work of the respiratory muscles (mainly the diaphragm and intercostals) accounts for about 2% of total O2 use. This reflects that ventilating the lungs at rest requires relatively little energy compared to the extensive metabolic activity occurring in other organs and tissues (brain, heart, liver, kidneys, muscles during daily activity). When breathing work increases—such as with airway obstruction, lung disease, fever, or exercise—the oxygen cost of breathing rises and the breathing muscles can consume a larger fraction of VO2, but at rest the typical figure is around 2%.

The amount of oxygen the body uses to power the act of breathing at rest is a small portion of total oxygen consumption. In a healthy resting adult, the work of the respiratory muscles (mainly the diaphragm and intercostals) accounts for about 2% of total O2 use. This reflects that ventilating the lungs at rest requires relatively little energy compared to the extensive metabolic activity occurring in other organs and tissues (brain, heart, liver, kidneys, muscles during daily activity). When breathing work increases—such as with airway obstruction, lung disease, fever, or exercise—the oxygen cost of breathing rises and the breathing muscles can consume a larger fraction of VO2, but at rest the typical figure is around 2%.