[Obstructive-sleep apnea syndrome: brain oxygenation measured with near-infrared spectroscopy. Preliminary results]

This study assessed cerebral oxygenation in four obstructive sleep apnea syndrome (SAOS) patients (age = 51.8 +/- 15 years, apnea-hypopnea index = 68-125 per hour), during sleep and waking time, using near infrared spectoscopy (NIRS), during a standard polysomnography. Oxyhemoglobin (HbO2, reflecting cerebral oxygenation), total hemoglobin (Hbt, reflecting cerebral blood volumes) and cerebral oxygen saturation (SaO2c = HbO2/Hbt), were compared to the data obtained in four snorers not presenting apneas (age = 51.8 +/- 6.6, apnea-hypopnea index = 2.6-6.2 per hour) examined in the same way. The main result was that HbO2 values were reduced in SAOS patients, both during sleep (at stage 2: 52.54 +/- 9.60 mumol/L versus 73.80 +/- 11.70 mumol/L) and during waking state (53.67 +/- 7.20 mumol/L versus 63.05 +/- 5.55 mumol/L). Hbt was also reduced in apneic patients as compared to snorers during waking state (72.73 +/- 13.90 mumol/L versus 96.05 +/- 6.30 mumol/L). During sleep, Hbt increased in a similar way for snorers and apneics (12.4% versus 13%), whereas HbO2 values were constant for apneics. SaO2c paralleled SaO2p in snorers and apneics, values for SaO2c being 20-30% lower than values for SaO2p. The difference in the values was probably due to the use of different monitoring techniques. Cerebral oxygenation and cerebral blood volumes were continuously low in apneic patients, and peripheral hypoxia was associated with same-range cerebral hypoxia. Cerebral hemodynamic mechanisms related to sleep, although in part efficient in apneic patients, were not able to increase cerebral oxygenation up to normal values.