The Challenges and Pitfalls of Detecting Sleep Hypopnea Using a Wearable Optical Sensor: Comparative Study

Area of Science:

• Sleep Medicine
• Respiratory Physiology
• Biomedical Engineering

Background:

• Obstructive sleep apnea (OSA) is a prevalent respiratory disorder with high undiagnosed rates due to diagnostic challenges.
• Wearable sleep trackers offer potential for cost-effective at-home diagnosis but cannot currently detect sleep hypopnea.
• Accurate measurement of oxygen desaturation (OD) is crucial for diagnosing sleep hypopnea.

Purpose of the Study:

• To compare arm OD (arm_OD) with fingertip OD (finger_OD) during sleep hypopneas.
• To evaluate the suitability of arm-based OD measurements for diagnosing OSA and assessing CPAP therapy effectiveness.

Main Methods:

• Simultaneous measurement of arm_OD and finger_OD during polysomnography in 30 OSA patients.
• Comparison of OD measurements during baseline sleep and continuous positive airway pressure (CPAP) titration.
• Analysis using Bland-Altman plots and t-tests to assess agreement and differences.

Main Results:

• A total of 2185 hypopneas were analyzed, with 668 during baseline and 1517 during CPAP.
• Mean difference between finger_OD and arm_OD was 2.86% during baseline and 1.83% during CPAP.
• Using a 3% OD drop criterion, arm_OD detected only 16.32% of baseline and 14.90% of CPAP hypopneas.

Conclusions:

• Arm OD measurements are physiologically lower than fingertip measurements in sleep hypopnea.
• The standard ≥3% OD drop criterion is inadequate for arm-based hypopnea detection.
• Current arm-based OD measurement methods are unsuitable for OSA diagnosis and CPAP assessment.