Upper airway lengthening caused by weight increase in obstructive sleep apnea patients.

BACKGROUND: The longer upper airway is more collapsible during sleep. This study aims to reveal relationships among upper airway length, weight, and obstructive sleep apnea (OSA), particularly to answer why the upper airway of OSA patients is longer than that of healthy people and why some obese people suffer from OSA while others do not. METHODS: We perform head and neck MRI on male patients and controls, and measure > 20 morphological parameters, including several never before investigated, to quantify the effect of weight change on upper airway length. RESULTS: The upper airway length is longer in patients and correlates strongly to body weight. Weight increase leads to significant fat infiltration in the tongue, causing the hyoid to move downward and lengthen the airway in patients. The apnea-hypopnea index (AHI) strongly correlates to airway length and tongue size. Surprisingly, a distance parameter h and angle ß near the occipital bone both show significant differences between healthy males and patients due to their different head backward tilt angle, and strongly correlates with AHI. The contributions of downward hyoid movement and head tilt on airway lengthening are 67.4-80.5% and19.5-32.6%, respectively, in patients. The parapharyngeal fat pad also correlates strongly with AHI. CONCLUSIONS: The findings in this study reveal that the amount of body weight and distribution of deposited fat both affect airway length, and therefore OSA. Fat distribution plays a larger impact than the amount of weight, and is a better predictor of who among obese people are more prone to OSA.

Three-dimensional analysis of upper airways in Class II malocclusion children with obstructive sleep apnea.

BACKGROUND: Morphometric evaluation of upper airways helps in identifying potential craniofacial anatomy that may predispose to pediatric obstructive sleep apnea (OSA). This study evaluated upper airway parameters three-dimensionally in children with OSA, with Class II malocclusion and a retrognathic mandible, to identify cutoff values for cone-beam computed tomography measurements that may predict the presence and severity of pediatric OSA. METHODS: The study comprised 47 growing children with OSA with Class II malocclusion and 47 low-risk OSA-matched controls. Upper airway was segmented into nasopharynx, oropharynx, and hypopharynx using cone-beam computed tomography and MIMICS16.0 software. Parameters included volume, minimum cross-sectional area (CSAmin), anterioposterior and lateral distances of CSAmin, and upper airway length. RESULTS: The volume, cross-sectional area (CSAmin), and anteroposterior and lateral distances of CSAmin were significantly decreased at the level of the oropharynx in patients with OSA. At the level of the hypopharynx, CSAmin was significantly narrower and upper airway length was significantly increased in patients with OSA. OSA predictive cutoff values were proposed as 41.36 mm2 CSAmin at the level of oropharynx, 52.45 mm2 CSAmin at the level of hypopharynx, and 55.47 mm upper airway length. Only CSAmin at the level of the oropharynx had an independent association with OSA severity (P = 0.021). CONCLUSIONS: Significant differences were found in the upper airway parameters of children with OSA compared with corresponding controls. CSAmin may represent part of the issues that play a role in the pathogenesis of OSA and may serve as a predictive of disease severity.

Epiglottis cross-sectional area and oropharyngeal airway length in male and female obstructive sleep apnea patients.

INTRODUCTION: Obstructive sleep apnea (OSA) is a male-predominant condition, characterized by repeated upper-airway collapse with continued diaphragmatic efforts during sleep, and is accompanied by severe physiological consequences. Multiple morphological aspects, including epiglottis cross-sectional area (CSA) and oropharyngeal airway length (OPAL), can contribute to airway collapsibility in the condition. This study focused on the effects of OSA severity, sex, and race on OPA dimensions. MATERIALS AND METHODS: Two high-resolution T1-weighted image series were collected from 40 mild-to-severe OSA subjects (age 46.9±9 years, body mass index 30.4±5.4 kg/m2, Apnea-Hypopnea Index score 32.8±22.5, 28 males) and 54 control subjects (47±9 years, 24.7±3.8 kg/m2, 32 males) using a 3 T magnetic resonance-imaging scanner. Caucasian, Asian, African-American, and "other" subjects constituted the study pool. Both image series were realigned and averaged, and reoriented to a common space. CSA and OPAL were measured, normalized for subject height, and compared between sexes and disease-severity levels in OSA and control subjects. RESULTS: Significantly reduced epiglottis CSA appeared only in severe OSA vs controls (P=0.009). OPAL increased significantly with OSA severity vs controls (mild, P=0.027; moderate, P<0.001; severe, P<0.001). OSA males showed increased CSA and greater OPAL than OSA females, which may underlie the increased proportion of affected males with higher apnea-hypopnea index scores. However, no significant differences appeared between CSA and OPAL measures for male and female controls, suggesting that airway morphology may not be the sole contributor for airway collapse. No ethnic or racial differences appeared for CSA or OPAL measures. CONCLUSION: Sex-based reductions in epiglottis CSA and increased OPAL in OSA subjects may enhance airway-collapse vulnerability, more so with greater disease severity, and partially underlie male vs female susceptibility to the sleep disorder.