What state is described as the Resting Expiratory Level (REL)?

Resting Expiratory Level (REL) refers to the state of equilibrium in the respiratory system where the elastic forces of the lungs and the thoracic cage are balanced. At this point, the air pressure within the lungs equals the atmospheric pressure, and no air movement occurs as a result. This is a critical concept in speech science, as it represents a baseline state from which both inhalation and exhalation are measured.

At REL, the respiratory muscles are in a relaxed position, allowing for efficient air exchange and facilitating phonation or speech when combined with other respiratory functions. Understanding this equilibrium is essential for speech-language pathology and respiratory physiology, as it highlights the natural state that supports optimal functioning of the respiratory system without additional muscular effort.