Criteria assessed  Score 

I. Study design (maximum score = 11 points) 

A. Time  Retrospective, 1 point; prospective, 2 point. 
B. Randomized sample  If stated, 1 point. 
C. Control group  If present, 1 point. 
D. Sample size  Subjects ≥ 29, 1 point; power of the study estimated before collection of data, 1 point. 
E. Sample gender  Both gender included and divided into different groups, 2 points; only male or female, 1 point; both gender included but not divided, 0 point. 
F. Objective  Clearly formulated, 1 point 
G. Selection criteria  If they are clearly described and relevant to the topic of the paper, 1 point. 
H. Baseline characteristics  Similar baseline characteristics, 1 point. 
II. Study measurements (maximum score = 9 points) 

A. Segmentation method (manually or automated) 
If clearly stated, 1 point. 
B. Part of airway 
If the part of airway mentioned consistent with the anatomic definition advocated by Schwab et al. [44] and GuijarroMartínez et al. [20], 1 point. 
C. Type of airway measurements  Volume, 1 point; partial volume, 1 point, Linear, 1 point; smallest cross section, 1 point. 
D. Airway measurements adjusted  Adjusted to head position (i.e. craniocervical inclination), 1 point; adjusted to a horizontal plane (i.e. FHP), 1 point. 
E. Method of acquisition  If clearly stated, 1 point. 
F. Blinding measurements method  If clearly stated and implemented, 1 point. 
III. Data analysis (maximum = 4 points) 

A. Statistical analysis  If clearly 5stated and appropriate for data, 1 point. 
B. Validation of measurements (error of the method) 
If it’s stated that the method used had been validated in the present paper or validated in early paper, 1 point. 
C. Data presentation 
If Pvalue stated, 1 point; if any variability measures (standard deviation, confidence interval, or range) stated, 1 point. 