Bedside approach in the diagnosis obstructive sleep apnea using postprandial oximetry testing: A comparative study with polysomnography

Introduction Due to the availability and cost issues in developing countries of polysomnography (PSG), there is a need for outpatient test for an initial assessment of the patients with suspected obstructive sleep apnea (OSA). Objectives Epworth sleepiness scale (ESS) is a widely used and best-validated scale for assessing daytime sleepiness, including dozing when sitting quietly after a lunch (no alcohol). This study introduces a novel screen test called postprandial oximetry test (POT) used during daytime. Methods This single-center prospective study included 101 patients (80 patients with suspected OSA and 21 patients without OSA suspicion). Berlin Questionnaire was used to determine the score/pretest probability of OSA patients, all chosen randomly. First, all the patients underwent POT in laboratory. Then we performed PSG. After lunch, while sleeping, the patients were monitored for 1 hour with pulse oximetry and standard electroencephalographic system. The oximetry saturation classification events with SpO2 was divided into two groups as normal or mild obstructive sleep apnea syndrome (OSAS), and moderate-to-severe OSAS. Below 90% SpO2 drops in a postprandial oximetry recordings were accepted as moderate-to-severe. Results The mean lowest oxygen saturation in PSG was 82.34 +/- 5.99, while it in POT were 87.42 +/- 1.39. A positive correlation was found between POT- and PSG-derived Apnoea-Hypopnoea Index (AHIs). The sensitivity and specificity in postprandial oximetry were 85% and 85.7%, respectively. The accuracy was 0.903 for POT. Conclusion POT may be useful as an outpatient test in the initial assessment of the patients with suspected OSA, serving as a gatekeeper for PSG.