10 - Oxygen

Abstract

•Oxygen moves down a partial pressure gradient between the inspired gas and its point of use in the mitochondria, where the oxygen partial pressure may be only 0.13 kPa (1 mmHg).•Significant barriers to oxygen transfer are between inspired and alveolar gas, between alveolar and arterial oxygen partial pressures and on diffusion from the capillary to the mitochondria.•Each 100 mL of arterial blood carries 0.3 mL of oxygen in physical solution and around 20 mL of oxygen bound to haemoglobin, which reduces to about 15 mL.dL−1 in venous blood.•Oxygen carriage by haemoglobin is influenced by carbon dioxide, pH, temperature and red blood cell 2,3-diphosphoglycerate; the molecular mechanism of haemoglobin is now well elucidated.•Glucose and other substrates are used to produce energy in the form of adenosine triphosphate (ATP), each glucose molecule yielding 38 molecules of ATP in the presence of oxygen, compared with only two molecules in anaerobic conditions.•Oxygen delivery is the total amount of oxygen leaving the heart per minute, and is about 1000 mL.min−1, compared with oxygen consumption of around 250 mL.min−1.