F25. Intranight variability of AHI can affect the efficiency of CPAP treatment

Abstract

Introduction Obstructive sleep apnea (OSA) is a common disease with severe health consequences most commonly treated with continuous positive airway pressure (CPAP) device. However, the adherence to CPAP treatment is often limited and the usage of the CPAP device can be only around 4 h per night after 1 month usage ( Chai-Coetzer et al., 2013 ). Possibly for this reason the benefits of the CPAP usage in terms of cardiovascular outcomes are not always obvious ( McEvoy et al., 2016 ). The severity of OSA is estimated with apnea-hypopnea-index (AHI) together with daytime symptoms. AHI may vary hour by hour during the night. In the current study, the aim was to investigate whether there is a difference in AHI during the first 4 h of sleep (possible CPAP adherence) and during the worst 4 h during the night. Methods 2002 ambulatory polygraphic recordings of suspected OSA patients were evaluated. The patients were divided into normal, mild, moderate and severe OSA categories based on their total AHI. Total AHI, AHI during the first 4 h and AHI during the worst 4 h during the recording were analyzed. AHI during the first and the worst 4 h were then compared. Wilcoxon signed ranks test was used to estimate the statistical significance of the differences. p Results There were 972, 508, 260 and 262 patients in normal, mild, moderate and severe OSA categories, respectively. We found a trend of increasing AHI towards the end of the night. The median total AHI in these categories were 1.5, 8.7, 20.7 and 47.6 events/h, respectively. The median differences between the AHI during the worst 4 h and the first 4 h of the recording were 0.8, 4.8, 10.4 and 9.8 events/h ( p Conclusion There were statistically and clinically significant differences between the median AHI values of the worst 4 h and the first 4 h of the night in all OSA severity categories. CPAP adherence has been reported to be around 4 h per night ( Chai-Coetzer et al., 2013 ) and the CPAP usage is probably typically focused on the first hours from the beginning of the night. For these reasons the benefits of the CPAP usage are probably not as linear as the simple time of adherence indicates. With limited adherence time, CPAP treatment is not always able to prevent severe cardiovascular outcomes ( McEvoy et al., 2016 ). If the CPAP usage could be directed to the worst hours of the night at the same adherence level it might provide better treatment results. The total AHI would decrease more when CPAP would be used during the worst hours instead the first hours of the night.