Inspiratory

Inspiratory is an adjective describing anything related to inspiration, the process of drawing air into the lungs. In physiology, inspiration is the first phase of the respiratory cycle, followed by expiration, the exhalation of air.

During quiet breathing, inspiration is largely an active process driven by the diaphragm and external intercostal muscles. The diaphragm contracts and moves downward, while the ribs are lifted to expand the thoracic cavity, creating negative pressure that draws air in. In more intense breathing, accessory muscles such as the sternocleidomastoid and scalene muscles may assist.

In respiratory measurements, several terms use inspiratory. Inspiratory reserve volume (IRV) is the extra amount of air that can be inhaled after a normal inspiration. Inspiratory capacity (IC) is the total amount of air that can be inspired after a normal exhalation, equal to tidal volume plus IRV. The rate and depth of inspiration are regulated by neural input and chemical receptors that monitor blood CO2 and O2 levels.

Clinical context: abnormal inspiratory effort or sounds can indicate airway obstruction, inflammation, or respiratory distress. Inspiratory stridor, a high-pitched sound during inhalation, suggests upper airway obstruction. In diseases affecting the inspiratory muscles or chest mechanics, such as diaphragmatic weakness or severe restrictive disorders, inspiratory performance may be reduced.

Etymology and usage: the term derives from Latin inspirare, “to breathe into,” composed of in- (into) and spirare (to breathe).

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