THE CARDIOVASCULAR EFFECTS OF OBSTRUCTIVE SLEEP APNEAS - ANALYSIS OF PATHOGENIC MECHANISMS

Obstructive sleep apnoeas (OSA) exert immediate marked cardiovascular effects, and may favour the development of systemic and pulmonary hypertension in the long-term. As for the pathogenesis of the acute cardiovascular changes, the first studies highlighted the role of OSA-induced hypoxia and mechanical changes. However, more recent work pointed to the role played by the arousal reaction terminating OSA, and to the activity of the autonomic nervous system during apnoea and inter-apnoeic phase. As for the pathogenesis of chronic cardiovascular changes, recent findings suggest that the link between OSA and systemic hypertension may be through an abnormal function of the carotid body and underline the importance of chronic intermittent hypoxia versus continuous hypoxia in the development of stable systemic hypertension. On the other hand, OSA do not appear to enhance strongly the development of stable pulmonary hypertension. In this review, we analyze OSA-induced cardiovascular changes with particular emphasis on to the interplay of the possible pathogenic mechanisms involved. Acute OSA-induced cardiovascular alterations during the apnoeic phase appear to result mainly from the mechanical effects of OSA, while during the interapnoeic phase they seem mostly determined by chemical factors (hypoxia, hypercapnia) and by the arousal reaction. In addition, the role of reflex changes elicited by resumption of ventilation should be reconsidered, since lung inflation seems to exert a positive effect on the cardiovascular changes occurring at the end of OSA. This would be in contrast with the inhibitory effects described as ''lung inflation reflex'', and deserves further study.