Probable obesity hypoventilation syndrome in a Korean medical intensive care unit: clinical characteristics and outcomes

Background/Aims: Obesity hypoventilation syndrome (OHS) is associated with morbidity and intensive care unit (ICU) utilization. However, data from Asian ICUs are limited. We evaluated the proportion, characteristics, and outcomes of probable OHS among obese patients admitted to a medical ICU (MICU) in Korea.Methods: We analyzed obese adults (body mass index [BMI] ≥ 27 kg/m²) admitted to the MICU at Seoul National University Hospital between 2016 and 2023. Probable OHS was defined as obesity with chronic hypercapnia (PaCO₂ ≥ 45 mmHg and bicarbonate ≥ 27 mmol/L) without alternative causes. Clinical characteristics and outcomes were compared between the probable OHS and obese non-probable OHS groups. Mortality was evaluated using inverse probability of treatment weighting (IPTW).Results: Among 3,660 MICU admissions, 531 patients (14.5%) were obese. The proportion of probable OHS was 0.4% (16/3,660) overall, 3.0% (16/531) among obese patients, and 6.5% (12/186) at BMI ≥ 30 kg/m². Obstructive airway disease was more prevalent in the probable OHS group. Most patients meeting probable OHS criteria went unrecognized during their stay in the MICU. Patients with probable OHS tended to have longer hospital stays (40 vs. 24 days, p = 0.083), despite lower illness severity at admission. Although unadjusted mortality was lower in the probable OHS group, IPTW-adjusted analyses showed no significant differences in in-hospital or 90-day mortality.Conclusions: This single-center study found that 3% of obese MICU patients had probable OHS. These findings suggest that underlying OHS may be overlooked in the ICU, highlighting the need for improved recognition and diagnostic strategies.