Manifestation of pulmonary hypertension during REM sleep in obstructive sleep apnea syndrome

The effect of sleep stage change on pulmonary circulation has not been well documented in patients with obstructive sleep apnea syndrome (OSAS). We in vestigated whether or not stage-specific change can affect pulmonary artery pressure (Ppa) in patients with OSAS. Thirty-one patients with OSAS underw ent right cardiac catheterization in the daytime and the following night, i ncluding 19 patients in whom Ppa could be measured throughout non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Ten of the 19 patients had daytime pulmonary hypertension (PH) defined by a mean Ppa ((Ppa) over bar) greater than or equal to 20 mm Hg. Then we analyzed Ppa response to hy poxia spontaneously occurring during the period of sleep apnea. The slopes of the regression lines between arterial oxygen saturation measured by puls e oximeter (Sp(O2)) and (Ppa) over bar curves were almost the same In both NREM and REM patient groups with or without daytime PH, whereas the respons e curve was significantly shifted upward in REM compared with NREM patients with daytime PH. Furthermore, Ppa was elevated more markedly in associatio n with REM burst, phasic REM, compared with tonic REM. We conclude that vas cular tone of pulmonary artery could be elevated in association with REM sl eep which is independent of the degree of hypoxia, and that this state-spec ific change is manifested in patients with daytime PH.