IMPAIRMENT OF CEREBRAL PERFUSION DURING OBSTRUCTIVE SLEEP APNEAS

Cerebral circulation was studied in six patients with obstructive slee p apnea (OSA) by transcranial Doppler. Cerebral blood flow velocity (C BFV), pulsatility index (Pi), intra-arterial radial blood pressure, tr anscutaneous blood gases, and respiration were recorded during sleep w ith or without apneas. There was a concomitant increase of mean arteri al pressure (($$$) over bar Pa) and CBFV by 11 +/- 6% (p < 0.001) and 15 +/- 6% (p < 0.001) compared with baseline at 5.1 +/- 2.4 and 5.3 +/ - 2.6 s, respectively, after apnea termination. ($$$) over bar Pa and CBFV decreased to a minimum of -8 +/- 2% (p < 0.001) and -23 +/- 8% (p < 0.001), respectively, below baseline at 19.8 +/- 5.0 and 19.4 +/- 4 .5 s after apnea. Values returned to baseline within 60 s, except duri ng repetitive apneas, which were associated with prolonged periods of reduced ($$$) over bar Pa and CBFV. Pi changed inversely to CBFV and r ose to 34 +/- 15% (p < 0.001) above baseline 19.5 +/- 5.5 s after the end of apnea because of a decrease in diastolic CBFV. There was a clos e correlation between ($$$) over bar Pa and CBFV(r = 0.67, p < 0.001), indicating that cerebral autoregulation is insufficient to protect th e brain from rapid systemic pressure changes in OSA. The findings sugg est that apneas during sleep are associated with profound changes in c erebral blood flow. Apnea-induced hypoxemia combined with reduced cere bral perfusion may predispose to nocturnal cerebral ischemia in patien ts with OSA.