[The occurrence of hypertension in patients with obstructive sleep apnea syndrome]

To determine the changes in blood pressure (BP) and its correlated factors in patients with obstructive sleep apnea syndrome(OSAS).

Retaining manometric tube in radial artery and polysomnography(PSG) were done synchronously in 13 patients with OSAS in whom was diagnosed by whole-night PSG. Oxygen therapy was given to two of the patients and NCPAP treatment was given to four of the patients on the following night.

(1) Six of the patients (46 percent) had daytime hypertension (SBP > 18.7 kPa and/or DBP > 12 kPa), the incidence of transient hypertension during apnea in 7 patients who do not have daytime hypertension was 86% (6/7). (2) Lowest oxygen saturation during sleep was significantly correlated with the level of SBP(r = -0.659, P < 0.05) and DBP(r = -0.677, P < 0.01) in awake, the baseline of SBP(r = -0.777, P < 0.01) and DBP (r = -0.590, P < 0.05) in NREM sleep and that of SBP(r = -0.585, P < 0.05) in REM sleep. In REM sleep, the changes in MBP showed significantly correlation with the changes in oxygen saturation during apnea (r = 0.598, P < 0.05). In NREM sleep, the changes in SBP were significantly correlated with apnea length(r = 0.580, P < 0.05). The changes in BP showed no correlation with apnea index in different sleep stages (P > 0.05). (3) Nocturnal elevation in BP disappeared in four patients who received NCPAP treatment, but not in two patients who received oxygen therapy.

The transient hypertension during apnea might be recurrent episodes in patients with OSAS who have normal daytime BP. Nocturnal hypoxemia and apnea length might play a role in nocturnal elevation in BP in patients with OSAS. Hypoxemia was not the major factor in BP elevation after obstructive apneas. Simple oxygen administration could not normalize the elevation in BP during apnea in patients with OSAS and NCPAP might be an appropriate therapy.