Hypoxia as a failure of respiratory homeostasis

Blood gas homeostasis is a vital part of the process of maintaining tissue oxygenation and in preventing acidosis arising from carbon dioxide accumulation. There is a need, therefore, for homeostatic processes to control lung function if tissue functions elsewhere are to be supported. The partial pressures of blood gases reflect those occurring within the lung alveoli during breathing but should be viewed as being representative of average alveolar composition since regional variation in the composition of alveolar gas exists within the lungs. Inadequate alveolar ventilation, changes in the regional distribution of ventilation or blood flow, and alterations to the alveolar-capillary membrane across which the gases must diffuse result in a failure to maintain blood gas homeostasis. The control of lung function is normally very precise but it is susceptible to extrinsic factors. It is important that nurses are aware of the risk of respiratory complication during and after surgery, and of the difficulties of providing effective therapies. Risk reduction and the need for monitoring should figure highly in care planning and delivery. Basic methods such as monitoring pulse rate and body temperature during recovery or in the post-surgical period can identify problems since hypoxaemia promotes a tachycardia and often pyrexia. These may be symptomatic of other problems, of course, and so are important means of detecting a variety of homeostatic failures.