Background: Obstructive sleep apnoea (OSA) has been described as a public health problem comparable to smoking in its impacts upon society.
Objective: To compare the differences in cranial base and airway morphology in Malay adults with and without OSA using finite element analysis (FEM).
Method: Lateral skull radiographs of 38 adult Malays aged 18-60 years were divided into two groups of 19 (13 male, 6 female). The first group consisted of 19 patients with OSA, defined as an apnoea-hypopnea index > 5/hr of sleep, diagnosed with overnight polysomnography. The second group consisted of 19 healthy, non-OSA control subjects. For each lateral skull radiograph 27 homologous landmarks, which encompassed the naso-oropharyngeal airway, were digitised using MorphoStudio software. The mean OSA and control 2D airway configurations were computed and subjected to t-tests and FEM.
Results: The mean 2D OSA airway was statistically different from the mean control airway (p < 0.01). Inter-landmark analysis revealed that the cranial base saddle angle was more acute in the OSA group (153.9 degrees +/- 3.4) compared to the control group (158.3 degrees +/- 2.5; p < 0.01). In addition, using pseudo-coloured FEM a relative 58 per cent decrease in nasopharyngeal airway area was found above and behind the soft palate. As well, a 32 per cent decrease in oropharyngeal airway area was located behind the base of the tongue, with a 23 per cent decrease in hypopharyngeal area near the level of the hyoid bone. In contrast, a 96 per cent increase in area associated with downward displacement of the hyoid bone was detected.
Conclusion: Functional airway impairments associated with OSA can be quantified and localised in Malay patients, and are predominantly associated with the morphology of the posterior regions of the cranial base.