ICU · Applied physiology

Applied Physiology — Cardiovascular, Respiratory, Renal, Neuro, GI and the Stress Response

Also known as Applied physiology · Oxygen delivery · Cardiac output determinants · Oxygen cascade · Oxyhaemoglobin dissociation curve · Venous return · Cerebral autoregulation · Dead space and shunt · Frank-Starling mechanism · Guyton cardiac function curve · Mean systemic filling pressure · Lung volumes and closing capacity · Hypoxic pulmonary vasoconstriction · Splanchnic circulation · Gut barrier and bacterial translocation · Stress response and the HPA axis · Critical illness hypermetabolism

The applied physiology that underpins every ICU intervention — the cardiovascular (the cardiac-output determinants of preload, afterload, contractility and heart rate; the Frank-Starling mechanism; the oxygen-delivery equation; the venous-return and the Guyton model; the cardiac and the vascular function curves and the mean systemic filling pressure; the Fick principle), the respiratory (the oxygen cascade; the oxyhaemoglobin dissociation curve and its shifts by the pH, the temperature, the 2,3-DPG and the CO2; the ventilation-perfusion matching; the dead space and the shunt; the compliance and the time constants; the lung volumes and the closing capacity; the work of breathing; the hypoxic ventilatory response and the carotid body; the hypoxic pulmonary vasoconstriction), the renal (the GFR determinants; the tubular sodium and water handling; the RAAS; the countercurrent multiplier; the acid-base handling), the neuro (the cerebral autoregulation; the Monro-Kellie doctrine; the cerebral perfusion pressure; the cerebral metabolic rate), the gastrointestinal (the splanchnic circulation and the gut barrier; the bacterial translocation; the hepatic clearance), and the stress response (the HPA axis and the cortisol; the catecholamines; the ebb-and-flow hypermetabolism; the non-thyroidal illness syndrome; the feeding strategy). Each system is applied to the critically ill patient — the shock, the ARDS, the AKI, the raised ICP, the multi-organ failure.

Checked against its sources on 2 Sept 2026