Factors Influencing the Level of Efficient Pressure of Continuous Positive Airway Pressure (cpap) in the Treatment of Obstructive Sleep Apnea (Osas)

Introduction: There are currently only little data available on the factors determining the choice between the use of fixed CPAP or automated CPAP (APAP) for OSAS treatment. Aims and objectives: In order to optimize this therapeutical strategy, we aimed to evaluate the parameters contributing to the determination of the level of efficient pressure (Peff) as well as pressure variability (Var) after 7 days of home treatment with an APAP. Methods: A multicenter prospective controlled study was conducted in 22 french centers. Initial clinical and polygraphic data were obtained before initiating a 7-day period using APAP allowing a variation of pressure between 4 and 20 cm Hg, and data obtained from the APAP were collected at the end of the study period including pressures levels and apnea hypopnea index (AHI). Peff was determined as the level of P95 with AutoSet S9 or P90 with PR1. Var was obtained by subtracting the median pressure (AutoSet S9) or the mean pressure (PR1) of the corresponding value of Peff. Results: 704 patients (mean age : 56.4 yrs ± 11.6, mean AHI : 51.7/h ± 20.8) were included. At day 7, the mean Peff was 11.3 cmH2O ± 2.7 and Var was 2.6 cmH2O ± 0.9. We found a high significant correlation between Peff and Var (rS = 0.59; p < 0.0001), and multiple regression analysis demonstrated that only AHI and the minumum nocturnal SpO2 (p <0.0001) could be considered as independant factors influencing Peff level. Conclusion: These results suggest that the higher Peff is, the higher the pressure variability is, more specifically in the most severe OSAS patients and could help to choose the optimal mode of CPAP.