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Between 1990 and 1995, 369 patients were investigated for obstructive sleep apnea syndrome (OSAS) by polysomnography. Among them, 248 patients with a mean Apnea-Hyponea index (AHI) of 37.7 per hour were treated by nasal continuous positive airway pressure (n-CPAP). Mean follow up was 39.5 +/- 20.4 months. In this group, 23 patients (9.2%) refused nCPAP immediately or after the first night and 39 (15.7%) gave up later. 15 patients (6%) died during the period of the study. The cumulative compliance reached 70% at 72 months. Non compliant patients usually gave up n-CPAP before the end of the first year. We compared the group of 150 patients always treated at the date of 31/12/95 with the group of 62 patients who refused nCPAP initially or gave up later. There was no difference in clinical parameters or polysomnographic data between the two groups. In 94 patients treated by nCPAP for more than a year we evaluated the outcome of AHI by a polysomnography performed after 72 hours of nCPAP cessation. Mean AHI of the group at this time was 38.2 +/- 20.3/h and was well correlated with the initial index (r = 0.41, p < 0.0001). However for 28 patients (29.7%) we observed, at the time of this second AHI determination, a variation (plus or minus) of at least 50% of the index. 6 patients, without any significative weigth loss, had an AHI below 5/h at this second determination. In this small group nCPAP was interrupted for 6 to 12 months, then another polysomnography was performed. At this time mean AHI was 42.4/h and clinical symptoms had reappeared in all patients. This study demonstrated that compliance to nCPAP in OSAS patients is good. No clinical or polysomnographic factors allow to predict non compliance. AHI is not modified by long term treatment with nCPAP.

Nocturnal oximetry can show nocturnal oxygen desaturation. This examination was proposed as an investigation for the early detection of the sleep apnoea syndrome (SAS). We have compared the results of nocturnal oximetry and polysomnography in 329 consecutive patients seen in the department of thoracic medicine for the early detection of the SAS between June 1990 and June 1995. The diagnosis of SAS was confirmed at the time of polysomnography using an hypopnoea/apnoea index (IAH) greater or equal to 15 per hour. Two parameters of oximetry were well correlated with IAH less than 15 per hour: if the mean oxygen saturation is greater than 92% and for less than five per cent of the time of the examination there was a saturation of less than 90%. The sensitivity was 89.7% and the specificity was 57.8%. Among the 48 false positive cases on oximetry 17 patients were found to be suffering from COPD and 31 patients were probably suffering from a syndrome of upper airways resistance or possibly from the hypoventilation obesity syndrome. Amongst the 22 false, negatives to oximetry 10 non COPD patients with an IAH of greater than 30 per hour and diurnal somnolence had important anomalies of the oro-pharyngeal pathway as the origin of their nocturnal apnoea. The 12 other false negatives were patients with moderate SAS with an IAH of between 15 and 20 per hour. Logistical analysis has shown the association of the two oximetric criteria (mean oxygen saturation or percentage of time with a saturation of less than 5%) with clinical criteria (body mass index and formation on diurnal somnolence from a questionnaire) would enable a probable diagnosis of SAS in 75% of cases. Our study shows that nocturnal oximetry used an early diagnosis test, associated with clinical and respiratory function data enables the number of requests for polysomnography to be reduced.

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Background and purpose: Obstructive sleep apnea syndrome (OSAS) is an independent risk factor for stroke. Impairment of cerebral autoregulation may play a potential role in the pre-disposition to stroke of OSAS patients. In this study, we aimed to assess dynamic cerebral autoregulation (DCA) during wakefulness in OSAS patients and a group of matched controls. Methods: Patients and controls were examined in the morning after an overnight complete polysomnography. Mean cerebral blood flow velocity (CBFV) in the middle cerebral artery and mean arterial blood pressure (ABP) were continuously recorded using transcranial Doppler and Finapres. DCA was assessed using the Mx autoregulatory index. Mx is a moving correlation coefficient between mean CBFV and mean ABP. More positive value of Mx indicates worse autoregulation. Results: Eleven OSAS patients (mean age ± SD; 52.6 ± 7.9) and 9 controls (mean age ± SD; 49.1 ± 5.3) were enrolled. The mean apnea–hypopnea index (AHI) in the OSAS group was of 22.7 ± 11.6. No significant difference was found between the two groups as for age, body mass index, mean ABP and endtidal CO2 pressure. Cerebral autoregulation was impaired in OSAS patients compared with controls (Mx index: 0.414 ± 0.138 vs. 0.233 ± 0.100; P = 0.009). The severity of autoregulation impairment correlated to the severity of the sleep respiratory disturbance measured by the AHI ( P = 0.003). Conclusion: Cerebral autoregulation is impaired in patients with OSAS during wakefulness. Impairment of cerebral autoregulation is correlated with the severity of OSAS. [ABSTRACT FROM AUTHOR]