425 Investigating the Utility of Routine Carbon Dioxide Measurements During Polysomnography in the Evaluation of Obese Adult Patients

Introduction With the increasing prevalence of obesity, the diagnosis of obstructive sleep apnea (OSA) and obesity hypoventilation syndrome (OHS) have also increased. Adding routine transcutaneous carbon dioxide (TcCO2) or end-tidal carbon dioxide sensors (EtCO2) may add beneficial information to the polysomnogram (PSG) and expand the diagnostic and treatment capabilities in this population. Our study looks at the use of this parameter in obese adults on whom CO2monitoring has been used. Methods We performed a retrospective chart review of obese adult patients (body mass index [BMI] >30) undergoing a PSG. We documented the EtCO2 values at baseline (supine awake) and during sleep. Correlations between the EtCO2 readings and BMI were reviewed. We excluded patients that had poor EtCO2 waveforms and patients with known preexisting hypoventilation syndromes, such a COPD. Results Fifty patients were identified between January and November 2020 at the Memorial Hermann Sleep Center. 54% were female and 46% were male with an average age of 55.3 years (range 26–73) and an average BMI for the cohort of 40.1 (SD +/-9.5). The average AHI on the diagnostic study (CMS criteria) was 30.9 events/hour (SD +/- 43) and the average oxygen desaturation nadir was 79%. Sixteen patients (32%) met diagnostic criteria for OHS based on the baseline awake EtCO2 which would have otherwise been missed without CO2 monitoring. When comparing the mean values of the ETCO2 between Group 1 whose BMI was less than 40 kg/m2 (39.9 mmHg) to Group 2 whose BMI was greater than 40 kg/m2 (45.9 mm Hg), the difference was statistically significant with a p-value is 0.001. Conclusion OHS is reported to have greater mortality when compared to OSA. CO2 monitoring is currently only routinely required in pediatric PSGs. Our review suggests a higher diagnostic yield of OHS in adults with the use of CO2 monitoring especially when morbidly obese. Given the alarming trend towards obesity in the US, this advocates for the routine use of CO2 monitoring in adult obese patients. Although more research is needed, we may draw a conclusion that there is meaningful data to support the use of routine ETCO2 monitoring in this adult patient population. Support (if any):