What is exhalation primarily characterized as?

Exhalation is primarily characterized as a passive process of relaxation due to the mechanics of the respiratory system. During normal exhalation, the diaphragm and intercostal muscles, which are responsible for inhalation, relax. This relaxation allows for the elastic recoil of the lungs and thoracic cavity, which pushes air out of the lungs without the direct use of energy or muscular effort. As the diaphragm rises and the rib cage lowers, the pressure within the thoracic cavity increases, facilitating the movement of air out of the lungs.

While there are circumstances where exhalation can become an active process, such as during intense physical exertion or forced breathing (which involves accessory muscles), the default mechanism under resting conditions is largely passive. This contrasts with inhalation, which actively requires energy through the contraction of respiratory muscles. Understanding this distinction is crucial for comprehending basic respiratory physiology in a combat medic context.