[Pulmonary artery hypertension and hypoxemia in sleep]

Sleep apnea syndrome is responsible for repeated and sometimes deep arterial oxygen desaturations occurring during apneas, followed by episodes of transient pulmonary hypertension (PH). In chronic obstructive pulmonary disease (COPD) patients with respiratory insufficiency, a worsening of hypoxemia occurs during sleep, due to alveolar hypoventilation and/or ventilation-perfusion mismatching. This hypoxemia is also responsible for pulmonary hypertensive dips due to pulmonary hypoxic vasoconstrictiveness. But there is presently no evidence that sleep-related and transient PH may lead to daytime and permanent PH, in either sleep apnea syndrome or COPD. In fact permanent PH seems to be related, in most cases, to the presence of daytime (permanent) hypoxemia.