breaths

A breath is the act of taking air into the lungs and then expelling it. It enables gas exchange, delivering oxygen to body tissues while removing carbon dioxide produced by metabolism.

During inhalation the diaphragm and intercostal muscles contract, expanding the chest and drawing air through the nose or mouth to the alveoli. Exhalation is typically passive, as the chest recoils, pushing air out. The brainstem regulates breathing by sensing blood levels of carbon dioxide and oxygen, adjusting rate and depth to maintain the body’s pH and gas balance.

Typical resting breathing in adults is about 12 to 20 breaths per minute, with a tidal volume around 500 milliliters per breath. Minute ventilation equals rate times tidal volume, roughly 6 liters per minute, adjusted for dead space in the airways that does not participate in gas exchange. Alveolar ventilation accounts for this and more directly reflects gas exchange efficiency.

Breathing patterns vary with activity, emotions, and health. Shallow or rapid breathing, deep slow breathing, and breath-holding (apnea) occur in different contexts, including exercise, stress, meditation, or medical conditions. Breath control techniques are used in medicine, singing, and athletics to optimize ventilation and calm the body.

Knowledge of breathing is central to pulmonology and critical care. Disorders such as asthma, chronic obstructive pulmonary disease, or restrictive conditions affect airflow and gas exchange. Understanding respiration also informs everyday practices, from posture and exercise to relaxation and speech.