What defines airway resistance (Raw)?

Airway resistance (Raw) is defined as the pressure difference that is required to drive a specific flow of gas through the airways. This relationship is captured by the formula for resistance in which airway resistance is calculated by dividing the change in pressure by the airflow rate. This means that if there is a larger pressure difference needed to achieve a certain flow rate, the airway resistance is considered to be higher.

This concept is central to understanding respiratory mechanics, especially in conditions such as asthma or chronic obstructive pulmonary disease (COPD), where airway resistance may significantly increase due to narrowed air passages. The other choices are related to pulmonary function but do not precisely define airway resistance: the volume of air in the lungs and total lung capacity pertain to lung volumes, while the speed of airflow refers to the velocity of gas movement, which is influenced by resistance but does not define it.