Respiration: ventilation

Publication date: November 2014 Source:Anaesthesia & Intensive Care Medicine, Volume 15, Issue 11 Author(s): Siân Davies , Upma Misra Ventilation is the process by which air moves into and out of the lungs and is made available for gas exchange across the alveolar-capillary membrane. Ventilation occurs automatically in a continuous rhythmic pattern without any conscious effort. It is controlled by both neural and chemical inputs and is concerned with the homeostasis of oxygen and carbon dioxide as well as having a role in acid–base balance. Inspiration is an active process. The diaphragm is the main muscle of inspiration, but other muscles can be involved. Expiration is normally a passive process during quiet breathing, but in certain disease processes may require energy expenditure. Resistance to gas flow in the airways is determined by a number of factors. Airway radius is the most important factor influencing resistance and gas flow changes from being turbulent to laminar as bronchi divide and cross-sectional area of the airways increases. Ventilation is not evenly distributed throughout the lungs and distribution is related to the compliance of alveoli in different areas of the lungs. Under normal circumstances, in the standing position, basal alveoli are the most compliant and are therefore preferentially ventilated.
Source: Anaesthesia and intensive care medicine - Category: Anesthesiology Source Type: research