[Critical study of the indications for long-term oxygen therapy. Chronic obstructive bronchopneumopathies]

Numerous studies have shown that longterm oxygen therapy in hypoxaemic patients with chronic airflow obstruction (BPCO) is capable of improving the prognosis and decreasing the risk of cardio-respiratory decompensation; in addition sometimes physical capacity and intellectual capacity is improved. Another result often noted is a reduction in the mean hospital stay which corresponds to an improvement in the quality of life. A PaO2 constantly below 55 mmHg (7.3 kPa) is defined by the majority of authors as a precarious state. At this level even a small change in alveolar ventilation or disturbance of distribution would lead to an important fall in the oxygen content of the arterial blood. The stability of the PaO2 during the weeks of respiratory reeducation with specially controlled medical treatment, as well as the willing consent of the patient and his family, are indispensable conditions for the prescription of OLT. When hypoxaemia is of moderate severity (PaO2 between 50 and 60 mmHg (6.6-8 kPa), prolonged medical treatment (with abstention from tobacco) for at least two months is advised and a study of complementary criteria to further validate the indications for oxygen. Such features would include a worsening of the hypoxaemia during exercise of 30 to 40 watts (PaO2 less than 50 mmHg, 6.6 kPa), an elevated haematocrit (greater than 55%), a rise of the P (A-a)O2 (greater than 30 mmHg or 4 kPa), a nocturnal desaturation even in the absence of apnoea (oxyhaemoglobin saturation (SaO2) of less than 80% for more than 50% of the time asleep). Added to these criteria are the radiological, echographic and clinical signs of the effect of hypoxaemia on the pulmonary circulation. Frank pulmonary arterial hypertension observed in hypoxaemia of moderate severity when the PaO2 is in the region of 55 mmHg and is an argument for the prescription of OLT. Amongst the developing criteria, exacerbations of respiratory encephalopathy, intellectual deterioration, progressive wasting, permanent ventilatory embarrassment with tachypnoea, should be borne in mind as the occasion arises. A schedule of 18 hours per day (without stopping for more than 3 hours) is necessary to obtain an improved survival and places a great demand on patient co-operation and on their environment. A prolonged educational programme is required. To achieve such a schedule the use of portable oxygen may be justified so that patients can lead a normal social life.(ABSTRACT TRUNCATED AT 400 WORDS)