Continuous oxygen therapy for hypoxic pulmonary disease: guidelines, compliance and effects

Continuous oxygen therapy (COT) has become widely accepted in the last 20 years in patients with continuous hypoxemia. This review focuses on guidelines for COT, adherence to these guidelines, and the effect of COT on survival, hospitalization, and quality of life. Guidelines for COT are mainly based on three randomized studies where documentation of hypoxemia (P(a)O2 <60mm Hg) and administration of oxygen at least 15 hours/day, are essential. There is less certainty concerning the required correction for hypoxemia, the attitude against current smokers with hypoxemia, the frequency and methods of follow up, and the effect of prescribing domiciliary oxygen to patients with temporary hypoxemia due to a clinically unstable condition (i.e. short-term oxygen therapy [STOT]). The administration of COT to patients with hypoxemic conditions other than COPD rests on extrapolation of data from COPD patients in the NOTT (Nocturnal Oxygen Therapy Trial) and MRC (British Medical Research Council) studies. Adherence to these guidelines is low in general, and very low in some cases. In some countries, STOT accounts for the majority of all prescriptions of domiciliary oxygen, and because nearly half of these patients do not meet the hypoxemia criteria at 3-month follow-up, re-evaluation is mandatory. Only 35%, approximately, of the patients are followed up, and this is one of the main reasons for poor adherence to the hypoxemia criteria. In order to improve the quality of surveillance of COT, more effort has to be put into education of the patients and staff responsible for COT, centralization of the domiciliary organizations, better equipment for ambulation and traveling, and regular follow-up preferably with home visits. The role of an oxygen register on the quality of surveillance of COT has to be determined. The beneficial effect of COT on survival is well established, and some evidence suggests that COT reduces hospitalization. It appears that ambulatory oxygen from liquid source or lightweight cylinders improves disease-specific quality of life modestly in selected patients who partake in regular outdoor activity. Whether COT from oxygen concentrators improves quality of life significantly is, at present, less clear.