Biometric study of the internal dimensions of subglottis and upper trachea in adult Indian population

The anatomy of the larynx and trachea is well described in literature, however the intraluminal dimensions and contour of the subglottis has not been well documented. Subglottis and trachea are dynamic structures and the internal dimensions and contours have been studied only on cadavers or by plain radiograph which has many technical and measurement errors. No data is available about the internal dimensions of the subglottic and trachea in Indian population. This is the first documented study to measure the dimensions of the trachea and subglottis in Indian population. The aim of this study is to measure the internal dimensions and contour of the subglottis and upper trachea of adult Indian population. We conducted cross-sectional, observational study in a university hospital in south India to measure the dimensions of the internal subglottic and upper tracheal lumen. CT scan with 3D reconstruction with multiplanar sections was used for precise measurements. Forty-eight subjects (30 male and 18 female) who had undergone CT scan of the neck and thorax for reasons other than airway compromise were included in the study. The internal coronal diameter (CD), sagittal diameter (SD), and circumference was measured at various levels from 5 to 70 mm below the level of glottis, in the subglottis and upper trachea. Measurements of the scan for each subject were done independently by a radiologist and ENT surgeon and average of the two were documented values of each subject. These measurements were then statistically analyzed using SSPS software. The mean CD of adult Indian male ranged from 13.18 to 17.68 mm. The average intraluminal circumference ranged from 48.82 mm at the subglottis 5 mm from the glottis to a maximum of 54.96 at 30 mm. The mean CD of adult Indian female ranged from 8.7 to 15.34 mm The average intraluminal circumference ranged from 36.5 at 5 mm and a maximum of 43.05 at 70 mm. The 95% CI for the coronal, sagittal and circumference of the subglottis and upper trachea for both genders have been calculated and discussed. We have observed that the average intraluminal dimensions of the subglottis and upper trachea in south Indian population is less than that reported in western literature and earlier studies.