Objectives Obstructive sleep apnea (OSA) has received much attention as a risk factor for perioperative complications and 68.5% of OSA patients remain undiagnosed before surgery. Facio-cervical characteristics may screen OSA for Asians due to smaller upper airways compared to Caucasians. Thus, our study aimed to explore a machine-learning model to screen moderate-severe OSA based on facio-cervical and anthropometric measurements.

Design A cross-sectional study.

Setting Data were collected from the Shanghai Jiao Tong University School of Medicine affiliated Ruijin Hospital between February 2019 and August 2020.

Participants A total of 481 Chinese participants were included in the study.

Primary and secondary outcome (1) Identification of moderate-severe OSA with apnea-hypopnea index (AHI)15 events·h⁻¹. (2) Verification of the machine learning model.

Results The SABIHC2 model (Sex-Age-Body mass index-maximum Interincisal distance-ratio of Height to thyro-sternum distance-neck Circumference-waist Circumference) was set up. The SABIHC2 model could screen moderate-severe OSA with an area under the curve (AUC)=0.832, the sensitivity of 0.916, and specificity of 0.749, and performed better than the STOP-BANG questionnaire, which showed AUC=0.631, the sensitivity of 0.487, and specificity of 0.772. Especially for asymptomatic patients (ESS < 10), the SABIHC2 model demonstrated better predictive ability compared to the STOP-BANG questionnaire, with AUC (0.824 vs. 0.530), sensitivity (0.892 vs. 0.348), and specificity (0.755 vs. 0.809).

Conclusion The SABIHC2 machine learning model provides a simple and accurate assessment of moderate-severe OSA in the Chinese population, especially for those without significant daytime sleepiness.

Participants with suspected OSA (snoring, witnessed apnea, or excessive daytime sleepiness, etc.) were enrolled in the study from Ruijin Hospital, Shanghai Jiao Tong University School of Medicine between February 2019 and August 2020. All participants underwent anthropometric measurements and subsequent overnight polysomnography (PSG). Participants were grouped according to their AHI gain into the following: 1) no or mild OSA (subjects without moderate-to-severe OSA: AHI <15 events·h⁻¹), 2) moderate-severe OSA (moderate to severe OSA: AHI ≥ 15 events·h⁻¹). Exclusion criteria: (1) Patients showing complications with severe respiratory diseases, such as severe COPD, interstitial lung disease, or acute asthma; (2) Patients showing complications with serious cardiovascular diseases such as acute myocardial infarction, acute heart failure, or chronic congestive heart failure (Grade III and IV); (3) Patients with mental illnesses who could not cooperate with the examination; (4) Patients who receiving non-invasive positive pressure ventilation therapy; (5) Patients who might have other sleep disorders under clinical evaluation.

Age, sex, height, weight, BMI, neck circumference (NC), waist circumference (WC), Epworth Sleepiness Scale (ESS), and STOP-BANG questionnaire were recorded. The STOP-BANG questionnaire is a scoring model consisting of eight questions and its scores are based on Yes/No answers (score: 1/0). The eight questions included snoring, tiredness, observed apnea, high blood pressure, BMI, age, neck circumference, and gender. Facio-cervical measurements including Mallampati score, MID, TMD, and TSD were measured. The Mallampati score was evaluated when participants were asked to sit upright and open their mouths as wide as possible. In grade I, the entire uvula, faucial pillar, and soft palate are visible. In grade II, part of the uvula and palate are visible. In grade III, the soft palate is visible, but the uvula is obscured.¹⁴ MID was recorded by asking the participant to sit upright and open the mouth as wide as possible.¹⁵ The TMD was measured as the straight distance between the thyroid notch and the lower border of the mental prominence, while the head was fully extended, and the mouth closed.¹⁶ TSD was measured as the distance between the thyroid notch and the upper border of the sternum. The distance was rounded to the nearest 0.5 cm. The ratios of height to TMD (H/TMD) and height to TSD (H/TSD) were calculated.¹⁶ 

There is no missing value.