Automatic event detection (AED) of residual apnea-hypopnea index (AHI) by ventilators is a current practice in sleep and mechanical ventilation Units but this methodology has not been validated in an unselected population of OSA patients. Aim of the present study was to assess in a “real-life” condition the reliability of AED during PAP therapy by the in-built software compared to full polysomnography during follow-up.

We enrolled 300 OSA patients (105 F; AHI 45.3 ± 27.8) already on Positive airway pressure (PAP) therapy: 53% of the patients were on CPAP while other modalities were used in the rest of the sample.

Overall, the built-in software identified residual obstructive AHI (AHI_PAP) > 5, 10 or 15 in 18.7, 8.6 or 4.6% of patients, respectively. By using AHI_PAP, 28.4% of patients were wrongly classified as “well controlled” despite a residual AHI_PSG>5 (6% considering a residual AHI_VENT >15); 7% of patients were classified as not controlled while AHI_PSG was <5 (1.4% considering a residual AHI_VENT >15). Type of ventilation, ventilator parameters, adherence to treatment and level of baseline or follow-up Epworth Sleepiness Scale score were similar between groups. The sensitivity and positive predicted values were very low. Positive likelihood ratio appears adequate only for residual AHI_PAP ≥10, but negative likelihood ratio was inconclusive for all the cut-off considered.

The results of the present study suggest a more cautious approach in the follow-up of OSA patients, since a protocol based only on AED detection and symptoms assessment may not be accurate especially for AHI_PAP<15.