Pathophysiology, diagnosis and treatment of severe chronic hypoxemia. Roleof long-term oxygen therapy.

The purpose of this article is to review the etiological and pathophysiolog ical aspects of chronic severe hypoxemia (CSH) and to determine the indicat ions of long-term oxygen therapy (LTOT). Three hypothesis are presented and analyzed: 1) CSH is harmful to the economy; 2) LTOT is therefore useful; 3 ) LTOT is not toxic and does not imply major risks than the benefits that i t offers. Changes are produced by prolonged exposure to low levels of O-2 l eading to a sustained increase in pulmonary artery pressure. Secondary pulm onary hypertension (SPH) due to chronic hypoxemia is much more subtle and l ess symptomatic than that produced by other pathologies. Chronic obstructiv e pulmonary disease is the most common cause of CSH; these patients have a poor prognosis associated to the hypoxemia and its effects, being a PaO2 be low 60 mmHg one of the most precise factors of mortality. Patients selectio n criteria for LTOT different sources for home oxygen therapy, methods of a dministration and finally an update of LTOT situation in our country and ab road are discussed.