Concerns arising from the calculation of the apnea-hypopnea index during CPAP-telemonitoring of patients with obstructive sleep apnea.

Background: Continuous Positive Airway Pressure (CPAP) telemonitoring is increasingly important in managing obstructive sleep apnea (OSA). The Apnea-Hypopnea Index reported by CPAP devices (AHI_flow) is used as a key indicator of treatment effectiveness. However, discrepancies in AHI_flow calculation rules between manufacturers may affect clinical decision-making. No prior studies have investigated whether manufacturers' choices to exclude certain apnea-hypopnea events from the AHI_flow calculation may influence the number of patients presenting an AHI_flow alert. The aim of this proof-of-concept study was not to compare the manufacturers with each other, but to evaluate, for each manufacturer, how the different possible ways of calculating AHI_flow influence the percentage of alert cases.

Methods: We conducted a retrospective analysis of 13,764 CPAP-treated OSA patients monitored on October 2, 2023. AHI_flow calculations were evaluated according to manufacturer-specific rules. When possible, we assessed the impact of excluding central hypopneas, events during major leaks, and/or ramp periods on the percentage of patients crossing the consensual AHI_flow alert threshold of ≥ 10 events/h.

Results: We identified significant disparities in AHI_flow calculations between manufacturers, which lead to significant differences in the number of patients flagged as being in an alert state. Excluding central hypopneas reduced the number of alert cases by 50%, while excluding apneas/hypopneas during major leaks or ramp periods reduced alerts by 20%.

Conclusions: Our proof-of-concept study highlights inconsistencies in AHI_flow calculations among CPAP manufacturers, raising concerns about patient care. Establishing standardized AHI_flow calculation criteria is essential to ensuring accurate monitoring and optimal patient safety.