The role of upper airway morphology in apnea versus hypopnea predominant obstructive sleep apnea patients: an exploratory study.

OBJECTIVE

The objective of this study was to investigate the association between upper airway morphology and apnea vs hypopnea predominance in patients with obstructive sleep apnea (OSA) syndrome.

METHODS

A retrospective study on consecutively CT scans obtained from 54 OSA patients and 53 non-snoring controls. CT scans were measured to evaluate upper airway and surrounding structures' morphologic characteristics. OSA patients (matched for age, gender and body mass index) compared as two groups; apneic group: apnea ratio >50% and hypopneic group: hypopnea ratio >50%. Morphologic characteristics were analyzed using Kruskal-Wallis test and Pearson's correlation test.

RESULTS

Apneic group (17 patients) showed 76.56% apnea rate and hypopneic group (37 patients) showed 78.46% hypopnea rate. Minimal lateral and anteroposterior dimensions of velopharynx in the apneic group (0.86 ± 0.73 and 0.21 ± 0.13 cm, respectively) was statistically lesser from that of the hypopneic group (1.2 ± 0.42 and 0.54 ± 0.22 cm, respectively). Minimum cross-sectional area of the velopharynx was also lesser in apneic group (0.21 ± 0.16 cm2) than that in hypopneic group (0.65 ± 0.38 cm2). Almost all upper airway parameters in both apneic and hypopneic groups were tended to be smaller than in controls.

CONCLUSION

Decrease in airway volume does not signify the type of respiratory event, but significant narrowing of velopharynx in both dimensions; thus having the narrowest value below a certain level causes more apnea. Advances in knowledge: We did not find a similar study when we did a literature search, showing the relationship of apnea vs hypopnea predominance and upper airway parameters in CT in patients with OSA.