Respiratory Physiology in Critical Illness

The practice of critical care medicine requires detailed knowledge of the practical aspects of respiratory physiology, including lung mechanics, the physiology of hypoxia, and the control of breathing. Before the lungs can enable gas exchange, air must move from the upper airway down a series of branching small airways and reach the alveoli. In the walls of the alveoli, capillaries form a dense network and receive blood flowing from the pulmonary artery before it flows to the pulmonary vein. Between the capillary network and the alveoli lies a thin blood-gas barrier through which oxygen and carbon dioxide move, chiefly by simple diffusion.