Inbreath

Inbreath is a term for the inward phase of breathing, generally synonymous with inhalation and inspiration in anatomical terms. It describes the process by which air is drawn into the lungs, as part of the respiratory cycle. While the common everyday term is inhalation, inbreath appears in some texts as a more archaic or stylistic variant.

During quiet inhalation, the diaphragm contracts and flattens, and the external intercostal muscles lift the rib cage, expanding the thoracic cavity. This expansion lowers intrapulmonary pressure below atmospheric pressure, allowing air to flow into the airways until the pressures equalize. Inhalation is typically an active process; exhalation is often passive at rest. In forced inhalation, accessory muscles such as the sternocleidomastoid and scalene muscles may assist.

In speech, singing, and some athletic activities, controlled inbreaths are important for timing and volume. In medical and physiological contexts, the modern terms inhalation or inspiration are preferred, with measurements such as tidal volume and inspiratory reserve volume used to describe capacity and airflow. Disorders affecting inhalation include restrictive lung diseases that limit chest expansion or neuromuscular diseases that weaken respiratory muscles, which can impair the ability to take deep or adequate breaths. Overall, inbreath is chiefly of historical or stylistic relevance in contemporary clinical language, where inhalation remains the standard term.