Fixed-pressure CPAP versus auto-adjusting CPAP: comparison of efficacy on blood pressure in obstructive sleep apnoea, a randomised clinical trial.

BACKGROUND: Millions of individuals with obstructive sleep apnoea (OSA) are treated by CPAP aimed at reducing blood pressure (BP) and thus cardiovascular risk. However, evidence is scarce concerning the impact of different CPAP modalities on BP evolution. METHODS: This double-blind, randomised clinical trial of parallel groups of patients with OSA indicated for CPAP treatment compared the efficacy of fixed-pressure CPAP (FP-CPAP) with auto-adjusting CPAP (AutoCPAP) in reducing BP. The primary endpoint was the change in office systolic BP after 4 months. Secondary endpoints included 24 h BP measurements. RESULTS: Patients (322) were randomised to FP-CPAP (n=161) or AutoCPAP (n=161). The mean apnoea+hypopnoea index (AHI) was 43/h (SD, 21); mean age was 57 (SD, 11), with 70% of males; mean body mass index was 31.3 kg/m(2) (SD, 6.6) and median device use was 5.1 h/night. In the intention-to-treat analysis, office systolic blood pressure decreased by 2.2 mm Hg (95% CI -5.8 to 1.4) and 0.4 mm Hg (-4.3 to 3.4) in the FP-CPAP and AutoCPAP group, respectively (group difference: -1.3 mm Hg (95% CI -4.1 to 1.5); p=0.37, adjusted for baseline BP values). 24 h diastolic BP (DBP) decreased by 1.7 mm Hg (95% CI -3.9 to 0.5) and 0.5 mm Hg (95% CI -2.3 to 1.3) in the FP-CPAP and AutoCPAP group, respectively (group difference: -1.4 mm Hg (95% CI -2.7 to -0.01); p=0.048, adjusted for baseline BP values). CONCLUSIONS: The result was negative regarding the primary outcome of office BP, while FP-CPAP was more effective in reducing 24 h DBP (a secondary outcome). TRIAL REGISTRATION NUMBER: NCT01090297.

Does oximetry contribute to the detection of apneic events? Mathematical processing of the SaO2 signal.

The purpose of this study was to assess the ability of continuous nocturnal oximetry to detect sleep apnea syndrome (SAS) and to recognize nonapneic oxyhemoglobin desaturations. Oxygen saturation oscillations, related to successive apneas in SAS or to apneic episodes in COPD or restrictive patients, were quantified using a new index: delta = 1/n sigma 1 n magnitude of delta(SaO2)/delta(t)(12-s intervals) Twenty-six patients (15 SAS, 8 COPD, and 3 restrictive patients) were included in a prospective study comparing nocturnal oximetry and polysomnography over 34 nights. In apneic patients, we found a strong correlation (r2 = 0.73, p less than 0.01) between time spent in apnea and the delta index. In COPD, the number of apneas was also correlated to the delta index (r2 = 0.92, p less than 0.01). A lower threshold for delta of 1.5 is accurate enough to detect apneas if initial SaO2 is greater than 93 percent. If initial SaO2 is greater than 93 percent, the delta threshold should be 0.8 (sensitivity 95 percent). Such a method could contribute to the accurate selection of patients for polysomnography.

[Can oximetry contribute to the detection of apnea? The use of a mathematical analysis of the oximetry signal]. / L'oxymétrie peut-elle contribuer à la détection des apnées? Apport du traitement mathématique du signal oxymétrique.

The aim of this study was to test the efficacy of nocturnal oximetry as a means of continuous recording of SaO2 in the identification of apnoeic events in the recognition of non-apnoeic desaturation. The oscillations of SaO2 in relation to successive periods of apnoea during the course of the sleep apnoea syndrome (SAS) or with apnoeic episodes in patients with chronic airflow obstruction (BPCO) or restricted disease, were identified using a new delta index quantifying the variations of SaO2 during the night. 26 successive patients in whom there was an indication for nocturnal oximetry were included in a prospective study comparing nocturnal oximetry and polysomnography during 34 nights. In the apnoeic patients we found a strong correlation (r = .85. p. less than .01) between the apnoeic period and the delta index. In BPCO the number of apnoea was correlated with the delta index (r = .96. p. less than .01). A minimal threshold of the delta index fixed at 1.5 was satisfactory for detecting apnoea if the initial SaO2 was less than 93%. The value of the adequate for affected detection ought to be fixed at .8 (95% sensitivity) when the initial SaO2 was greater than 93%. A detection of apnoeic events thus seems possible by this method.

[Development of nocturnal desaturation in 35 patients with chronic obstructive bronchopneumopathy (COBP). Relation to functional and hemodynamic data]. / Evolution des désaturations nocturnes de 35 patients BPCO. Relation avec les données fonctionnelles et hémodynamiques.

35 patients with chronic airflow obstruction in a stable state were studied using nocturnal oximetry on two occasions with an interval of 25 +/- 10 months between them. First we studied the predicted value for the pulmonary function factors during the day to compare with nocturnal desaturation. On the second occasion we compared the progress of the desaturation indices and the outcome of the functional and hemodynamic data. The PaO2, the PaCO2 and the VEMS/CV ratio (FEV1/VC) were the only elements during waking which correlated with the degree of nocturnal desaturation. In spite of this correlation and the fact that the confidence intervals were large, the predictable element of these daytime measurements remained weak in daily practice. The progress between the two oximetric measurements of the PaO2 and the PaCO2 as well as the fall in the FEV1 (VEMS) was strongly linked to the evolution of desaturation during sleep. This progressive aspect shows the value of nocturnal oximetry in patients who are evolving towards alveolar hypoventilation. Finally, the outcome of pulmonary arterial pressure appears predictable as a result of the progress of nocturnal desaturation.