Influence of sleep posture on response to oral appliance therapy for sleep apnea syndrome

STUDY OBJECTIVE: This study evaluated the effect of sleep posture on oral appliance therapy to elucidate the interindividual difference of response to the device. DESIGN: Seventy-two unselected patients with sleep apnea syndrome were studied polysomnographically before and after insertion of the individually fabricated and adjusted device. Sleep positions were measured using a body position sensor. The patients were classified into three groups; supine, lateral and prone groups, according to the position in which apneas were most frequently observed. SETTING: N/A. PATIENTS OR PARTICIPANTs: N/A. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: The mean apnea-hypopnea index (AHI) of all patients before treatment [43.0+/-25.6 (SD)] was significantly (p<0.0001) decreased after insertion of the appliance (21.6+/-18.3). The device decreased the mean AHI significantly from 29.8 to 11.3 in the supine position and 5.5 to 1.6 in the prone position, and increased, but not significantly, from 7.7 to 8.7 in the lateral posture. The supine (n=44) and prone (n=13) groups showed significant reduction of AHI with the oral appliance, while the lateral group (n=15) revealed only a slight decrease, although not significantly. Responders defined by AHI<10 accounted for 61.4% in the supine group, 0% in the lateral group and 84.6% in the prone group. Responders defined by a 50% drop in AHI accounted for 84.1%, 6.7%, and 46.7%, respectively. CONCLUSIONS: The effectiveness of oral appliance therapy is greatly influenced by sleep posture. Sleep posture recorded by polysomnography may be useful to predict the future success or failure of the device.     

Oropharyngeal collapse predicts treatment response with oral appliance therapy in obstructive sleep apnea

STUDY OBJECTIVES: To examine whether primary oropharyngeal collapse of the upper airway during sleep predicts treatment success with oral appliance therapy in patients with obstructive sleep apnea. DESIGN: Prospective physiologic study. SETTING: Multidisciplinary sleep disorders clinic in a university teaching hospital. PATIENTS: Twelve treatment-na?ve adult patients with obstructive sleep apnea (apnea-hypopnea index > or = 10/h and at least 2 of the following symptoms: snoring, fragmented sleep, witnessed apneas, or daytime sleepiness). INTERVENTION: Custom-made mandibular advancement splint (MAS). MEASUREMENTS AND RESULTS: A baseline diagnostic polysomnogram confirmed AHI > or = 10 per hour. During the following acclimatization period, a custom-made adjustable MAS was incrementally advanced until maximum comfortable mandibular protrusion was reached. A second polysomnogram with MAS in situ determined efficacy. Following a 1-week washout period, a final sleep study was performed using multisensor catheters (with and without MAS, in random order during the same night) to determine upper-airway closing pressures and the site or sites of upper-airway collapse. MAS resulted in significant improvements, mean +/- SEM, in AHI (22.0 +/- 2.6 vs 9.2 +/- 1.9/h, p < .01) and upper-airway closing pressures during stage 2 non-rapid eye movement sleep (-1.1 +/- 0.3 vs -2.8 +/- 0.5 cm H2O, p < .01). All 4 patients with primary oropharyngeal collapse achieved an AHI < 5 per hour. Only 1 of the 8 patients with primary velopharyngeal collapse achieved an AHI < 5 per hour. Oropharyngeal collapse, compared with velopharyngeal collapse, predicted treatment success with MAS (p < .02). CONCLUSIONS: These preliminary data suggest that primary oropharyngeal collapse of the upper airway during sleep is an important predictor of treatment outcome with MAS therapy.     

Influence of nasal resistance on oral appliance treatment outcome in obstructive sleep apnea

It has been recognized that nasal airway resistance (NAR) is elevated in patients with OSA. However, little is known regarding the influence of nasal resistance on mandibular advancement splint (MAS) treatment outcome in OSA patient. We hypothesized that nasal resistance differs between MAS responders and nonresponders and therefore may influence treatment outcome. Thirty-eight patients with known OSA underwent polysomnography while wearing a custom-made MAS. Treatment outcome was defined as follows: Responders (R) > or =50% reduction in AHI, and Nonresponders (NR) as <50% reduction in AHI. NAR was measured using posterior rhinomanometry in both sitting and supine positions, with and without MAS. The mean AHI in 26 responders was significantly reduced from 29.0 +/- 2.9/h to 6.7 +/- 1.2/h; P < 0.01). In 12 nonresponders there was no significant change in AHI (23.9 +/- 3.0/h vs 22.0 +/- 4.3/h; P=ns). Baseline NAR was significantly lower in responders in the sitting position compared to nonresponders (6.5 +/- 0.5 vs 9.4 +/- 1.0 cm H2O; P < 0.01). There was no significant change in NAR (from baseline) with MAS in either response group while in the sitting position, but in the supine position NAR increased significantly with MAS in the nonresponder group (11.8 +/- 1.5 vs. 13.8 +/- 1.6 cm H2O/L/s; P < 0.01). Logistic regression analysis revealed that NAR and BMI were the most important predictive factors for MAS treatment outcome. These data suggest that higher levels of NAR may negatively impact on treatment outcome with MAS.     

戴用口腔矫治器后阻塞性睡眠呼吸暂停低通气综合征患者舌骨力学的有限元分析

背景：采用三维有限元对下颌骨、气道、舌骨等共同建模进行研究的报道较少。 目的：通过建立下颌骨、气道、舌骨以及周围肌肉组织的模型,模拟戴用矫治器使下颌前伸改变气道形态的状况,在下颌骨上进行前伸加载,分析舌骨的生物力学表现。 方法：选取1名确诊为阻塞性睡眠呼吸暂停低通气综合征的男性患者,螺旋CT扫描眼眶下缘至甲状软骨图像,导入Mimics10.01软件分别提取各组织,Imageware10再对得到的文件点云进行处理,由ANSYS 10.0等软件生成三维有限元模型。在下颌骨上分别加载2,4,6,8 mm的前伸量,观察舌骨的生物力学表现。 结果与结论：上气道的应力主要集中在软腭及口咽部,舌骨上的应力主要集中在与下颌、气道相连的肌肉处。随着下颌前伸量加大,应力大小随伸长量增加而增大,舌骨随着肌肉的牵拉主要沿前上方移动。结果说明三维有限元法能够建立具有较高几何相似性及力学相似性的模型,是阻塞性睡眠呼吸暂停低通气综合征病理研究方法的扩充。     

Association of obstructive sleep apnea with severity of patients hospitalized for acute asthma

BackgroundStudies suggest that obstructive sleep apnea (OSA) is associated with suboptimal disease control and worse chronic severity of asthma. However, little is known about the relations of OSA with acute asthma severity in hospitalized patients.ObjectiveTo investigate the association of OSA with acute asthma severity.MethodsThis is a retrospective cohort study (2010-2013) using State Inpatient Databases from 8 geographically diverse states in the United States. The outcomes were markers of acute severity, including mechanical ventilation use, hospital length of stay, and in-hospital mortality. To determine the association of interest, we fit multivariable logistic regression models, adjusting for age, sex, race/ethnicity, primary insurance, household income, patient residence, comorbidities, hospital state, and hospitalization year. We repeated the analysis for children aged 6 to 17 years.ResultsAmong 73,408 adult patients hospitalized for acute asthma, 10.3% had OSA. Coexistent OSA was associated with a significantly higher risk of noninvasive positive pressure ventilation use (14.9% vs 3.1%; unadjusted odds ratio, 6.48; 95% CI, 5.88-7.13; adjusted odds ratio, 5.20; 95% CI, 4.65-5.80), whereas coexistent OSA was not significantly associated with the risk of invasive mechanical ventilation use. Patients with OSA had 37% longer hospital length of stay (unadjusted incidence rate ratio, 1.37; 95% CI, 1.33-1.40); this significant association persisted in the multivariable model (incidence rate ratio, 1.13; 95% CI, 1.10-1.17). The in-hospital mortality did not significantly differ between groups. These findings were consistent in both obesity and nonobesity groups and in 27,935 children.ConclusionAmong patients hospitalized for acute asthma, OSA was associated with a higher risk of noninvasive positive pressure ventilation use and longer length of stay compared with those without OSA.     

Mean platelet volume is associated with disease severity in patients with obstructive sleep apnea syndrome

OBJECTIVE:Obstructive sleep apnea syndrome is associated with cardiovascular diseases and thromboembolic events. The mean platelet volume (MPV) is a predictor of cardiovascular thromboembolic events. The aim of the present study is to investigate the association between the MPV and disease severity in patients with obstructive sleep apnea syndrome.METHODS:We prospectively included 194 obstructive sleep apnea syndrome patients without cardiovascular disease (mean age 56.5±12.5 years) who were undergoing sleep tests. An overnight full laboratory polisomnography examination was conducted on each patient. The patients were divided into 3 groups according to the apnea-hypopnea index (AHI): (1) AHIlow group: 5≤AHI<15, (2) AHImid group: 15<AHI≤30, and (3) AHIhigh group: AHI>30.RESULTS:The highest MPV values were found in the AHIhigh group compared with other groups (p<0.05 for all). Multiple linear regression analysis indicated that the MPV was associated with the AHI (β=0.500, p<0.001) and the high sensitivity C-reactive protein (hs-CRP) level (β=0.194, p=0.010).CONCLUSION:The MPV is independently associated with both disease severity and inflammation in patients with obstructive sleep apnea syndrome.     

Polysomnography with an epiglottic pressure catheter does not alter obstructive sleep apnea severity or sleep efficiency

Pharyngeal and oesophageal manometry is used clinically and in research to quantify respiratory effort, upper‐airway mechanics and the pathophysiological contributors to obstructive sleep apnea. However, the effects of this equipment on respiratory events and sleep in obstructive sleep apnea are unclear. As part of a clinical trial (ANZCTRN12613001106729), data from 28 participants who successfully completed a physiology night with an epiglottic catheter and nasal mask followed by a standard in‐laboratory polysomnography were compared. The apnea–hypopnea index was not different during the physiology night versus standard polysomnography (22 ± 14 versus 23 ± 13 events per hr, p = 0.71). Key sleep parameters were also not different compared between conditions, including sleep efficiency (79 ± 13 versus 81 ± 11%, p = 0.31) and the arousal index (26 ± 11 versus 27 ± 11 arousals per hr, p = 0.83). There were, however, sleep stage distribution changes between nights with less N3 and rapid eye movement sleep and more N1 on the physiology night, with no difference in N2 (53 ± 15 versus 48 ± 9, p = 0.08). However, these changes did not increase next‐day sleepiness. These findings indicate that while minor sleep stage distribution changes do occur towards lighter sleep, epiglottic manometry does not alter obstructive sleep apnea severity or sleep efficiency. Thus, epiglottic manometry can be used clinically and to collect detailed physiological information for research without major sleep disruption.     

Comparison of the effects of depressive symptoms and apnea severity on fatigue in patients with obstructive sleep apnea: a replication study

BACKGROUND: Links between fatigue and depressive symptoms in medically ill patients are well-documented; however, few studies controlled for illness severity. Obstructive sleep apnea (OSA) is a common, frequently devastating disease that often includes daytime sleepiness and fatigue. Fatigue is also a hallmark depressive symptom. We previously reported that depressive symptoms explained ten times the variance in fatigue in OSA patients as did OSA severity itself (respiratory disturbance index, oxyhemoglobin saturation). OSA severity explained 4.2% of variance in fatigue while depressive symptoms explained an additional 42.3%. Here, we report a replication of these findings in a new, independent sample. METHODS: 56 untreated OSA patients had their sleep monitored with polysomnography on the UCSD GCRC. Participants completed the Center for Epidemiologic Studies-Depression (CESD), Profile of Mood States (POMS) and Medical Outcomes Studies (MOS) surveys. Data were analyzed using hierarchical linear regression. RESULTS: OSA severity explained 13.4% (p=0.022) of variance in POMS fatigue while CESD scores explained an additional 24.5% (p<0.001). Results were robust to changes in the scales used to measure these constructs. LIMITATIONS: Cross-sectional design precludes determination of direction of causality. Assessment of depressive symptoms and fatigue was based on validated self-report measures. CONCLUSIONS: These results reaffirm that depressive symptoms are dramatically and independently associated with worse fatigue in OSA patients. While the independent contribution of OSA severity varied between studies, depressive symptoms were the strongest predictor of fatigue in both studies. Assessment and treatment of mood symptoms-not just treatment of OSA itself-might reduce fatigue in these patients.     

Vigilance in patients with obstructive sleep apnea and surgical patients

Aim

The Marburg vigilance test (VigiMar) is a vigilance task implemented as a four-choice reaction time task with long duration and low stimulus rate. It tests readiness for reaction under monotonous conditions characterized by sensory deprivation. This study was conducted to compare test results of subjects without sleep disorders to those of patients with untreated obstructive sleep apnea (OSA). In addition, whether patients treated for OSA by continuous positive airway pressure (CPAP) exhibited improvements in vigilance testing and whether subjects without sleep disorders have stable test results in a retest after 2 days were investigated. As test results are given for test thirds separately, these were used to determine whether there was a time-on-task effect for patients with untreated OSA and to check for internal consistency of the VigiMar test.

Patients and methods

A total of 20 patients with OSA and 20 surgical patients (knee arthroscopy) between 25 and 65 years of age were included. All patients were male. Vigilance testing was performed on the day before CPAP treatment was started or on the day before arthroscopy and 2 days later after the second CPAP night or on the first day after the surgical procedure, respectively.

Results

In the baseline vigilance test, reaction times of OSA patients were longer than those of surgical patients, especially during the last third of the test. After 2 nights CPAP, reaction times of OSA patients improved to the same level as those of surgical patients who exhibited homogenous results in baseline and postintervention testing.

Conclusion

The VigiMar test is suitable for the assessment of impaired vigilance. Its internal consistency is high, retest reliability is satisfactory, and it is sensitive for changes in vigilance after only 2 nights CPAP treatment.     

阻塞性睡眠呼吸暂停患者体位改变致流体向头颈部迁移的研究

目的当人体由立姿或坐姿改变为睡眠时的卧姿时,下肢流体会向头颈部迁移,使得上气道变窄。研究体位改变时阻塞性睡眠呼吸暂停(obstructive sleep apnea,OSA)患者头颈部组织中流体重新分布的过程,对于理解流体迁移在OSA患者气道阻塞上扮演的角色具有重要的意义。本研究通过测量OSA重度患者随着体位改变,在不同时刻腿部流体量,以及颈部和腿部几何参量,验证迁移流体量随时间非线性变化的假设。方法对于9名睡眠呼吸暂停低通气指数AHI30的重度患者,进行整夜多导睡眠监测,记录睡眠状态及AHI的变化,并测量站立、刚刚仰卧、仰卧15 min,及早上起床前仰卧诸时刻的腿部流体量以及颈围、腿围、踝围等几何参量,分析迁移流体量随时间的变化规律。结果由立姿改为仰卧后,几乎有总迁移量1/5的流体立刻发生迁移;仰卧15 min后迁移量升至1/3。睡眠监测显示受试者进入睡眠时间为(301±183)min。通过数据曲线拟合可推算出,仰卧30 min后流体迁移量将升至总迁移量的1/2。结论在OSA重度患者中,体位改变后,向头颈部迁移的流体量随时间以强非线性规律变化。相比于整夜的流体迁移量,在患者进入睡眠前,主要的流体迁移过程已基本完成。     

Association between obstructive sleep apnea severity and glucose control in patients with untreated versus treated diabetes

The purpose of this study was to determine whether the association between obstructive sleep apnea severity and glucose control differs between patients with newly diagnosed and untreated type 2 diabetes, and patients with known and treated type 2 diabetes. This multicentre cross‐sectional study included 762 patients investigated by sleep recording for suspected obstructive sleep apnea, 497 of whom were previously diagnosed and treated for type 2 diabetes (treated diabetic patients), while 265 had no medical history of diabetes but had fasting blood glucose ≥126 mg dL^?1 and/or glycated haemoglobin (HbA_1c) ≥6.5% consistent with newly diagnosed type 2 diabetes (untreated diabetic patients). Multivariate regression analyses were performed to evaluate the independent association between HbA_1c and obstructive sleep apnea severity in treated and untreated patients with diabetes. In untreated diabetic patients, HbA_1c was positively associated with apnea–hypopnea index (P = 0.0007) and 3% oxygen desaturation index (P = 0.0016) after adjustment for age, gender, body mass index, alcohol habits, metabolic dyslipidaemia, hypertension, statin use and study site. The adjusted mean value of HbA_1c increased from 6.68% in the lowest quartile of the apnea–hypopnea index (<17) to 7.20% in the highest quartile of the apnea–hypopnea index (>61; P = 0.033 for linear trend). In treated patients with diabetes, HbA_1c was associated with non‐sleep variables, including age, metabolic dyslipidaemia and insulin use, but not with obstructive sleep apnea severity. Obstructive sleep apnea may adversely affect glucose control in patients with newly diagnosed and untreated type 2 diabetes, but may have a limited impact in patients with overt type 2 diabetes receiving anti‐diabetic medications.     

Effects of short-term CPAP withdrawal on neurobehavioral performance in patients with obstructive sleep apnea

STUDY OBJECTIVE: Changes in sleep parameters and neurobehavioral functioning were systematically investigated after an acute (1 night) and short-term (7 nights) period of withdrawal from continuous positive airway pressure (CPAP) treatment and 1 subsequent night of CPAP reintroduction in patients with obstructive sleep apnea. DESIGN: Repeated-measurement within-subject design. SETTING: Sleep laboratory, university teaching hospital. PARTICIPANTS: Twenty participants receiving optimal CPAP therapy for > or = 12 months. INTERVENTIONS: CPAP withdrawal. MEASUREMENTS AND RESULTS: Polysomnograms were performed on Night 0 (with CPAP), Night 1 and Night 7 (without CPAP) and Night 8_R (with CPAP). Acute CPAP withdrawal resulted in the recurrence of sleep-disordered breathing with sleep disruption, hypoxemia, and increased subjective sleepiness. Short-term CPAP withdrawal exacerbated hypoxemia, increased subjective and objective sleepiness and poor mood ratings. Neurobehavioral functioning assessed using the Psychomotor Vigilance Task was impaired following Night 7 and associated with hypoxemia and changes in morning levels of tumor necrosis factor-alpha. However, other neurobehavioral measures were not affected. Autonomic arousals measured via respiratory-related reductions in finger blood volume by peripheral arterial tonometry decreased from Night 1 to Night 7. On Night 8_R, reintroduction of CPAP treatment eliminated most airway obstruction, maintained oxygenation, and reversed daytime sleepiness and some vigilance decrements. CONCLUSION: Despite recurrence of sleep-disordered breathing with increased sleepiness and impaired vigilance, most neurobehavioral variables were unaffected by CPAP withdrawal. The reduction in vigilance appeared to be associated with worsened hypoxemia and changed levels of tumor necrosis factor-alpha. Resumption of CPAP treatment had immediate benefits on sleep consolidation and subjective sleepiness.     

Comparison of the effects of continuous positive airway pressure,oral appliance and exercise training in obstructive sleep apnea syndrome

OBJECTIVE:

There are several treatments for obstructive sleep apnea syndrome, such as weight loss, use of an oral appliance and continuous positive airway pressure, that can be used to reduce the signs and symptoms of obstructive sleep apnea syndrome. Few studies have evaluated the effectiveness of a physical training program compared with other treatments. The aim of this study was to assess the effects of physical exercise on subjective and objective sleep parameters, quality of life and mood in obstructive sleep apnea patients and to compare these effects with the effects of continuous positive airway pressure and oral appliance treatments.

METHODS:

Male patients with moderate to severe obstructive sleep apnea and body mass indices less than 30 kg/m2 were randomly assigned to three groups: continuous positive airway pressure (n = 9), oral appliance (n = 9) and physical exercise (n = 7). Polysomnographic recordings, blood samples and daytime sleepiness measurements were obtained prior to and after two months of physical exercise or treatment with continuous positive airway pressure or an oral appliance. Clinicaltrials.gov: NCT01289392

RESULTS:

After treatment with continuous positive airway pressure or an oral appliance, the patients presented with a significant reduction in the apnea-hypopnea index. We did not observe changes in the sleep parameters studied in the physical exercise group. However, this group presented reductions in the following parameters: T leukocytes, very-low-density lipoprotein and triglycerides. Two months of exercise training also had a positive impact on subjective daytime sleepiness.

CONCLUSIONS:

Our results suggest that isolated physical exercise training was able to modify only subjective daytime sleepiness and some blood measures. Continuous positive airway pressure and oral appliances modified the apnea-hypopnea index.     

Effects of nasal pathologies on obstructive sleep apnea

Increased airway resistance can induce snoring and sleep apnea, and nasal obstruction is a common problem in snoring and obstructive sleep apnea (OSA) patients. Many snoring and OSA patients breathe via the mouth during sleep. Mouth breathing may contribute to increased collapsibility of the upper airways due to decreased contractile efficiency of the upper airway muscles as a result of mouth opening. Increased nasal airway resistance produces turbulent flow in the nasal cavity, induces oral breathing, promotes oscillation of the pharyngeal airway and can cause snoring.     

Endothelial dysfunction and C-reactive protein in relation with the severity of obstructive sleep apnea syndrome

STUDY OBJECTIVES: To investigate flow-mediated dilatation (FMD) and C-reactive protein (CRP) levels in patients with obstructive sleep apnea syndrome (OSAS) in relation with the severity of respiratory disturbances and hypoxemia. DESIGN: After subjects had completed nocturnal polysomnography, FMD was measured in the brachial artery, and blood samples were obtained to determine serum CRP levels. SETTING: Sleep laboratory in Seoul National University Bundang Hospital. PATIENTS: Ninety men: 22 normal controls, 28 subjects with mild to moderate OSAS, and 40 with severe OSAS. MEASUREMENTS AND RESULTS: FMD was found to be correlated with oxygen desaturation index (ODI), percentage of time below 90% O2 saturation, average O2 saturation, lowest O2 saturation, systolic blood pressure, apnea hypopnea index (AHI), and body mass index. In addition, CRP was correlated with body mass index, waist-to-hip ratio, neck circumference, diastolic pressure, average O2 saturation and percentage of time below 90% O2 saturation but not with AHI. Stepwise multiple regression showed that the ODI was a significant determinant of FMD (adjusted R2 = 10%, beta = -0.33, P < 0.01). In addition, body mass index (beta = 0.25, P < 0.05) and waist-to-hip ratio (beta = 0.21, P < 0.05) were found to be significantly correlated with CRP (adjusted R2 = 12%, P < 0.05), independently of other factors. There was no correlation between FMD and CRP. CONCLUSION: As a marker of nocturnal hypoxemia, ODI rather than AHI might better explain the relationship between OSAS and FMD. Because body mass index and waist-to-hip ratio were identified as risk factors of high serum CRP in OSAS, obesity should be considered when predicting cardiovascular complications in OSAS.     

CSF hypocretin measures in patients with obstructive sleep apnea

The majority of patients with narcolepsy-cataplexy were reported to have very low cerebrospinal fluid (CSF) hypocretin-1 (orexin-A) levels. The hypocretin-1 levels of secondary excessive daytime sleepiness (EDS) disorders are not known. In this study, we found that CSF hypocretin levels in the patients with obstructive sleep apnea syndrome were within the control range. The low hypocretin levels seem to reflect only the presence of cataplexy and DR2 positive in narcoleptics but not EDS itself.     

Effects of exercise training on autonomic modulation and mood symptoms in patients with obstructive sleep apnea

We evaluated the effects of exercise training (ET) on the profile of mood states (POMS), heart rate variability, spontaneous baroreflex sensitivity (BRS), and sleep disturbance severity in patients with obstructive sleep apnea (OSA). Forty-four patients were randomized into 2 groups, 18 patients completed the untrained period and 16 patients completed the exercise training (ET). Beat-to-beat heart rate and blood pressure were simultaneously collected for 5 min at rest. Heart rate variability (RR interval) was assessed in time domain and frequency domain (FFT spectral analysis). BRS was analyzed with the sequence method, and POMS was analyzed across the 6 categories (tension, depression, hostility, vigor, fatigue, and confusion). ET consisted of 3 weekly sessions of aerobic exercise, local strengthening, and stretching exercises (72 sessions, achieved in 40±3.9 weeks). Baseline parameters were similar between groups. The comparisons between groups showed that the changes in apnea-hypopnea index, arousal index, and O₂ desaturation in the exercise group were significantly greater than in the untrained group (P<0.05). The heart rate variability and BRS were significantly higher in the exercise group compared with the untrained group (P<0.05). ET increased peak oxygen uptake (P<0.05) and reduced POMS fatigue (P<0.05). A positive correlation (r=0.60, P<0.02) occurred between changes in the fatigue item and OSA severity. ET improved heart rate variability, BRS, fatigue, and sleep parameters in patients with OSA. These effects were associated with improved sleep parameters, fatigue, and cardiac autonomic modulation, with ET being a possible protective factor against the deleterious effects of hypoxia on these components in patients with OSA.     

Evaluation of the upper airway in patients with obstructive sleep apnea

Multiple methods have been used to study the structure and physiological behavior of the upper airway (UA) in patients with obstructive sleep apnea (OSA). Valuable information may be obtained from the physiologic measurement of pressure and resistance along the UA, as well as from imaging techniques that include: direct or fiberoptic visualization, cephalometric roentgenograms, fluoroscopy, acoustic reflection, computerized tomography, and magnetic resonance imaging. This review summarizes the information that each of these methods has contributed to our understanding of the UA. The results obtained with these different methodologies have generally been complementary with structural narrowing being identified in the majority of patients with OSA. This narrowing is usually focal and located in the velopharyngeal or retropalatal segment of the UA. This is also the predominant site of initial UA collapse. Although obesity with enlargement of soft tissue structures is considered the predominant mechanism leading to UA narrowing, abnormal craniofacial development on a genetic or developmental basis plays an important contributory role.