Short-duration nocturnal hypoxemia and persistent pulmonary hypertension.

Can daily short-duration hypoxemia (4-8 hours) induce pulmonary hypertensio n and right ventricular hypertrophy? A clinical model of this type of hypox emia does exist: isolated nocturnal hypoxemia in patients with obstructive sleep apnea syndrome (OSAS) or chronic obstructive pulmonary disease (COPD) . By investigating the pulmonary, hemodynamics of these patients, it should be possible to determine whether nocturnal hypoxemia alone can induce pulm onary hypertension. Although nocturnal hypoxemia (in OSAS as well as in COP D) can induce acute episodes of pulmonary hypertension, it would not appear that nocturnal hypoxemia alone would be sufficient to provoke permanent di urnal pulmonary hypertension. This is rite conclusion of recent studies con cerning diurnal pulmonary hemodynamics in OSAS and COPD patients exhibiting minimal hypoxemia during the day but significant nocturnal desaturation. T he therapeutic consequences of these data, particularly ill COPD are import ant: current evidence is insufficient to treat with nocturnal oxygen therap y COPD patients who have minimal diurnal hypoxemia but significant nocturna l desaturation.