What does a manometer measure in the context of respirometry?

In the context of respirometry, a manometer measures the pressure of gases, including oxygen, in relation to the atmospheric (outside) air pressure. This measurement is crucial for understanding how well oxygen is being delivered to the lungs and, subsequently, into the bloodstream. Monitoring the pressure differences helps assess respiratory function and can indicate conditions such as hypoxemia (low blood oxygen levels) or hypercapnia (excessive carbon dioxide in the bloodstream).

In clinical settings, ensuring that the oxygen pressure is at an appropriate level compared to atmospheric pressure is vital for effective patient management, especially in those with respiratory conditions. A manometer provides the necessary data for this analysis.

The other options are not accurate in relation to what a manometer specifically measures. While temperature, volume of exhaled air, and gas exchange efficiency are all important aspects of respiratory health, they are measured by different instruments and methods not involving a manometer. Thus, option B accurately describes the primary function of a manometer in respirometry.