Novel Type IV Monitoring Device With Advanced Oximetry Indicators Offers Accurate Diagnosis of Obstructive Sleep...

Type IV sleep monitors offer a low-burden option for obstructive sleep apnea (OSA) screening, yet their accuracy is often limited by motion artifacts and variability in signal-processing methods. The PM50-B is a wrist-worn Type IV device that combines high-sampling-rate (200 Hz) photoplethysmography (PPG)-based oximetry with wrist actigraphy to reduce motion artifacts and employs an adaptive SpO₂ waveform-based desaturation detection algorithm. This study aimed to validate the diagnostic performance of the PM50-B against reference sleep studies.

In this prospective observational study, adults with suspected OSA underwent simultaneous overnight recording with the PM50-B and a reference test: in-laboratory polysomnography (Type I), unattended polysomnography (Type II), or Type III home sleep apnea testing (HSAT). Oximetry and actigraphy signals were processed using a standardized workflow incorporating motion-artifact attenuation, signal stabilization, and sleep-wake estimation. From the SpO₂ signal, hypoxemia metrics were derived, including the oxygen desaturation index ODI2.5_5 (≥ 2.5% desaturation lasting ≥ 5 s/h of total sleep time), cumulative time with SpO₂ < 90% and < 95% (CT90, CT95), and lowest SpO₂. Agreement with the reference apnea-hypopnea index (AHI) was assessed using intraclass correlation coefficients, and diagnostic accuracy was evaluated at clinically relevant AHI thresholds.

A total of 475 participants were analysed (Type I, n = 37; Type II, n = 32; Type III, n = 406). ODI2.5_5 showed moderate-to-good agreement with AHI (ICC = 0.710) and good discrimination for moderate-to-severe OSA (AHI ≥ 15 events/h), with an under the curve (AUC) of 0.925 (sensitivity 81.20%, specificity 91.00%). Diagnostic performance was consistent across reference modalities (AUC range, 0.928-0.983).

The PM50-B provides clinically acceptable accuracy for OSA screening when combined with a standardized signal-processing approach, particularly in comparison with Type III HSAT. ODI2.5_5 emerged as the strongest diagnostic metric, while CT90, CT95, and lowest SpO₂ provided complementary characterization of nocturnal hypoxemia.