# Novel Type IV Monitoring Device With Advanced Oximetry Indicators Offers Accurate Diagnosis of Obstructive Sleep Apnea in Adults

## TL;DR

A new wrist-worn sleep monitor accurately detects obstructive sleep apnea in adults using advanced oximetry and motion compensation.

## Contribution

The PM50-B device introduces an adaptive desaturation detection algorithm that improves diagnostic accuracy in Type IV sleep monitoring.

## Key findings

- ODI2.5_5 showed good agreement with AHI (ICC = 0.710) and strong discrimination for moderate-to-severe OSA (AUC = 0.925).
- Diagnostic performance was consistent across different reference sleep study types (AUC range 0.928–0.983).
- The device's adaptive algorithm improves temporal consistency and reduces event identification ambiguity compared to conventional methods.

## Abstract

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.

As a Type IV sleep monitoring device, PM50‐B provides clinically acceptable accuracy for OSA screening when combined with a standardized signal‐processing approach. Compared with conventional ODI calculation methods, the proposed desaturation detection framework—incorporating adaptive baseline definition, persistence criteria at desaturation onset, and stable recovery requirements—provides improved temporal consistency and reduces ambiguity in event identification. This physiologically grounded approach contributes to more robust alignment between oximetry‐derived indices and AHI‐based disease classification.