Oxygen

Abstract

The role of supplemental oxygen in the relief of dyspnea is both physiologi- cally interesting and clinically important. Despite the almost parallel advances in our understanding of the mechanisms of dyspnea (1) and the pathophysiology of hypoxemia, the precise relationship between them remains unclear. The extent to which an increase in inspired oxygen con- centration will improve the PaO2 will vary depending on the magnitude of the mismatch between ventilation and perfusion. Understanding the sig- nificance of an increase in PaO2 as part of the management of dyspnea is all the more challenging as many profoundly dyspneic patients have only mini- mal hypoxemia. Most countries have developed programs for domiciliary oxygen therapy in which supplemental oxygen is funded according to established criteria, derived mainly from two well designed multicenter randomized controlled trials involving chronic obstructive pulmonary disease (COPD) patients with resting hypoxemia (2,3). Although resting hypoxemia is a clearly stated criterion for domiciliary oxygen therapy, some clinicians prescribe supplemental oxygen for patients with only minimal resting hypoxemia in an effort to alleviate their incapacitating dyspnea, increase their functional exercise capacity and improve their health status.