Influence of tongue/mandible volume ratio on oropharyngeal airway in Japanese male patients with obstructive sleep apnea.

OBJECTIVES: The objective of this study was to investigate the influence on the upper airway of the size ratio of tongue and mandible (T/M ratio) with 3D reconstructed models from computed tomography (CT) data.

STUDY DESIGN: The subjects were 40 OSA male patients. The age of the patients ranged from 25 to 77 years, with an average age of 52.6 ± 12.5 years. The body mass index (BMI) of the patients ranged from 20.1 to 35.8 kg/m(2), with an average BMI of 25.4 ± 3.4 kg/m(2). All patients underwent a full-night polysomnography. The mean AHI for our subjects was 23.6 ± 18.3 events per hour. CT imaging examinations were carried out in each patient. The mandible and airway volume (between posterior nasal spine [PNS] and the tip of the epiglottis) were segmented based on Hounsfield units, automatically or semi-automatically, and their volume was calculated from the number of voxels. The tongue was carefully outlined, and the inside of the tongue was smeared on each of the axial, frontal, and sagittal planes with a semi-automatic segmentation tool. The tongue/mandible (T/M) ratio was calculated from the volume of the mandible and the tongue. In addition, we investigated simple correlations between our anatomical variables and BMI, age, and AHI.

RESULTS: In this study, the mean tongue and mandible volume were 79.00 ± 1.06 cm(3) and 87.80 ± 1.21 cm(3), respectively. As BMI increases, tongue volume increases (P = .004) and airway volume decreases (P = .021). However, no significant correlation was found between severity of OSA (AHI) and other variables. On the other hand, there was a negative correlation between airway volume and T/M ratio (P = .046).

CONCLUSION: As tongue volume increases with BMI, the posterior airway is affected, and thus is likely to be involved in the development of OSA; however, in this study there was no correlation between the severity of sleep apnea (AHI) and other variables in the study.