Eupnée

Eupnée, or eupnée, is a term used in physiology and clinical medicine to describe normal, quiet breathing at rest. It denotes a regular, unlabored breathing pattern with adequate tidal volume and stable rhythm, without respiratory distress. Eupnea is distinguished from conditions such as dyspnea (shortness of breath), apnea (cessation of breathing), tachypnea (rapid breathing), and bradypnea (slow breathing).

Physiology and control of eupnea involve the brainstem respiratory centers. The dorsal and ventral respiratory groups in the medulla, assisted by the pontine respiratory group, generate and modulate the basic rhythm of breathing. Chemoreceptors in the carotid bodies and the brainstem sense carbon dioxide, oxygen, and pH levels and adjust respiratory drive accordingly. Mechanoreceptors in the lungs provide feedback on lung stretch and airway resistance, helping to stabilize breathing. Voluntary control from the cerebral cortex can briefly override reflexive patterns, but eupnea typically relies on automatic, autonomic regulation.

Characteristics and typical values in healthy adults include a resting tidal volume of about 0.5 liters per breath and a breathing rate of roughly 12–20 breaths per minute, yielding a minute ventilation of about 6–8 liters per minute. Eupneic breathing is generally regular in rhythm, with minimal use of accessory muscles and limited variation in depth or rate between breaths. Sleep and quiet activity can influence pattern slightly, but eupnea is maintained unless underlying pathology imposes respiratory burden.

Clinical relevance and variation: eupnea serves as the baseline respiratory pattern against which abnormalities are judged. Variations can occur with age, fitness, altitude, and chronic diseases; deteriorations may progress to dyspnea or abnormal ventilation. Etymology traces to Greek eu- (“well, good”) and pnéa (“breath”).