Long term domiciliary oxygen therapy in chronic obstructive pulmonary disease.

Chronic respiratory failure is a terminal event for many types of chronic respiratory dis- order.Supplemental oxygen forms a fundamental part of treatment but its application is not easy and it has to be conducted for long periods of time.Long term oxygen will, of necessity, be given mostly in the home environment.It must be distinguished from short term oxygen administration for acute respiratory failure where the aims are quite different and intertwined more positively with mechanical ventilatory support.Long term oxygen therapy (LTOT) utilises low dose supplementation of the inspired air to achieve an inspired oxygen concentration of approximately 30%.The figure was deter- mined by early studies in chronic obstructive airways disease (COPD), the commonest cause of chronic respiratory failure.' Substantial elevation of arterial carbon dioxide tension (Paco2) had to be avoided.Higher oxygen concentrations interfered adversely with ventilatory control and ventila- tion/perfusion relationships in. the lung.Subsequently, low dose techniques have been applied to all causes of chronic respiratory failure although this may not be appropriate optimal treatment in respiratory conditions where hypercapnia is not a problem.