Beyond Polysomnography: Study Reveals Peripheral Arterial Tonometry-Based Testing Proves Effective in OSA Diagnosis

A recent study demonstrated the utility of peripheral arterial tonometry (PAT)-based devices in diagnosing obstructive sleep apnea (OSA), particularly during the COVID-19 pandemic. The study highlighted the correlation between OSA severity and various physiological parameters. The authors suggest that these devices offer a viable alternative for OSA diagnosis, especially in resource-constrained settings or when polysomnography (PSG) is not feasible.

These findings are published in Indian Journal of Sleep Medicine in June 2025.

Obstructive Sleep Apnea (OSA) affects nearly 1 billion people globally and an estimated 104 million in India. Although polysomnography (PSG) remains the gold standard for diagnosis, limited access has led to endorsement of Home Sleep Apnea Testing (HSAT). Peripheral arterial tonometry (PAT)-based devices, which measure blood flow and oxygenation, are increasingly used to assess OSA severity and cardiovascular risk. This retrospective study evaluated a PAT-based device at an Indian tertiary care center, highlighting its relevance during the COVID-19 pandemic when remote diagnostics were essential.

Researchers retrospectively analyzed 55 patients with symptoms suggestive of OSA and high STOP-BANG or Epworth Sleepiness scores using an FDA-approved PAT-based device (NightOwl™). Patients with prior OSA or conditions mimicking OSA were excluded, and PSG was not feasible due to the pandemic. Data from March 2022 to February 2023 were evaluated based on device-recorded physiological parameters.

Most participants were male (74.5%) and overweight or obese (81.1%). Of the 55 patients, 50 were diagnosed with OSA, including 27 classified as severe. The device showed satisfactory performance, with only one test failure reported.

Key Findings from the Study are:

The study established significant correlations between OSA severity and various physiological parameters:

• Nocturnal Hypoxia: Minimum oxygen saturation (SpO2​) showed a strong negative correlation with the Apnea-Hypopnea Index (AHI) (R = –0.764). Severe OSA cases exhibited the lowest minimum SpO2​ levels, with 26 out of 27 severe patients displaying levels below 80%.

• T90 Values: Nocturnal hypoxia, measured by T90 (percentage of cumulative time spent below 90% oxygen saturation), correlated noticeably with OSA severity. Severe OSA categories had significantly higher average T90 values compared to mild or moderate cases.

• Cardiac Manifestations: Ectopic beats were prevalent in the OSA-positive cohort, occurring in 62% of diagnosed cases, supporting findings that cardiac arrhythmias are common in OSA patients.

• Other Correlations: A strong correlation was identified between the Oxygen Desaturation Index (ODI > 3%) and AHI values (R = 0.97). However, no significant correlation was found between AHI values and Body Mass Index (BMI).

Commenting on the findings, Col (Dr) Manu Chopra, Professor & Head, Dept of Respiratory Medicine, Army institute of Cardiothoracic Sciences, AFMC, Pune, noted, “Using a simple finger-based home sleep test, we were able to reliably diagnose obstructive sleep apnea and assess its severity in patients with high clinical suspicion. This shows that validated PAT-based devices can serve as a practical alternative to laboratory sleep studies, particularly in settings where access to polysomnography is limited.”

He further emphasized the real-world challenges associated with wider implementation, stating, “Wider adoption of home sleep testing will require adequate patient education, physician familiarity with interpreting device-generated data, and clear pathways for referral to polysomnography when results are inconclusive.”

The study highlights PAT-based devices as practical diagnostic tools where PSG access is limited. It emphasizes the importance of multi-night testing due to AHI variability and suggests that OSA severity assessment should extend beyond AHI, incorporating parameters such as nocturnal hypoxia (T90) and ODI to better guide cardiovascular risk management.

Reference: Chopra M, Tripathi S, Upadhyay M, Tyagi R, Kishore K. Analyzing Obstructive Sleep Apnea Patients Diagnosed with Peripheral Arterial Tonometry-based Diagnostic Device: Retrospective Study from Indian Tertiary Care Center. Indian Sleep Med 2025; 20 (2):35-40.