Pharyngeal shape and dimensions in healthy subjects, snorers, and patients with obstructive sleep apnoea

The effect of pharyngeal structures on the severity of obstructive sleep apnea

BACKGROUND/OBJECTIVE

Obstructive sleep apnea (OSA) is characterized by complete or partial cessation of breathing during sleep. The tongue is suggested as a possible anatomical site causing airway obstruction. However, the role of other pharyngeal structures in the development of OSA remains unclear. We designed a study using both the apnea-hypopnea index (AHI) and the oxygen saturation measurements to assess the severity of OSA. We aimed to identify critical anatomical structures of the upper airway that correlate with the severity of OSA and to evaluate the utility of magnetic resonance imaging (MRI) markers to detect possible OSA in patients without overt symptoms.

MATERIALS AND METHODS

The study included participants referred to the neurology outpatient clinic from the check-up unit. Participants were grouped as controls, mild, moderate, or severe OSA according to the AHI. A cranial MRI with a field of view (FOV) encompassing the upper airway structures was obtained from all participants. The areas of the tongue and the uvula were measured on the sagittal images by drawing the boundaries of the tissues manually. The posterior air space (PAS) area was evaluated from regions of interest in five parallel planes.

RESULTS

Of 105 participants, 30 were controls, 27 had mild, 25 had moderate, and 23 had severe OSA. The moderate and severe OSA groups did not differ in oxygen saturation levels during sleep. Therefore, patients with moderate and severe OSA were combined into one group (moderate/severe OSA). The area of the tongue was significantly larger in the moderate/severe OSA group compared to the control group. Both the tongue and the uvula areas showed a significant positive correlation with the AHI.

CONCLUSION

Our findings suggest that the tongue and uvula have prominent roles in the severity of OSAS. It may be useful to measure these structures with MRI to screen for at-risk individuals without overt OSA symptoms.

Comparison of PAS and adenoids in patients with and without maxillary micrognathia before orthodontic treatment

OBJECTIVE

Craniofacial anomalies are widely discussed as predisposing factors of breathing disorders. Since many more cofactors exist, this study investigated the association between maxillary micrognathia and morphological changes of posterior airway space and adenoids in these patients.

MATERIAL AND METHODS

Cephalometric radiographs of n = 73 patients were used for data acquisition. The patients were divided into two groups according to certain skeletal characteristics: maxillary micrognathia (n = 34, 16 female, 18 male; mean age 10.55 ± 3.03 years; defined by a SNA angle < 79°) and maxillary eugnathia (n = 39, 19 female, 20 male; mean age 10.93 ± 3.26 years; defined by a SNA angle > 79°). The evaluation included established procedures for measurements of the maxilla, posterior airway space and adenoids. Statistics included Kolmogorov-Smirnov-, T- and Mann-Whitney-U-Tests for the radiographs. The level of significance was set at p < 0.05.

RESULTS

The cephalometric analysis showed differences in the superior posterior face height and the depth of the posterior airway space at palatal level among the two groups. The depth of the posterior airway space at mandibular level was the same for both groups, just as the size of the area taken by adenoids in the nasopharynx.

CONCLUSIONS

Skeletal anomalies affect the dimension of the posterior airway space. There were differences among the subjects with maxillary micrognathia and these with a normal maxilla. However, the maxilla was only assessed in the sagittal direction, not in the transverse. This study showed that the morphology of the maxilla relates to the posterior airway space whereas the adenoids seem not to be affected.

CLINICAL RELEVANCE

Maxillary micrognathia is significantly associated with a smaller depth of the posterior airway space at the palatal level compared to patients with maxillary eugnathia.

Time-Dependent Fluid-Structure Interaction Simulations of a Simplified Human Soft Palate

Obstructive Sleep Apnea Syndrome (OSAS) is a common sleep-related disorder. It is characterized by recurrent partial or total collapse of pharyngeal upper airway accompanied by induced vibrations of the soft tissues (e.g., soft palate). The knowledge of the tissue behavior subject to a particular airflow is relevant for realistic clinic applications. However, in-vivo measurements are usually impractical. The goal of the present study is to develop a 3D fluid-structure interaction model for the human uvulopalatal system relevant to OSA based on simplified geometries under physiological conditions. Numerical simulations are performed to assess the influence of the different breathing conditions on the vibrational dynamics of the flexible structure. Meanwhile, the fluid patterns are investigated for the coupled fluid-structure system as well. Increasing the respiratory flow rate is shown to induce larger structural deformation. Vortex shedding induced resonance is not observed due to the large discrepancy between the flow oscillatory frequency and the natural frequency of the structure. The large deformation for symmetric breathing case under intensive respiration is mainly because of the positive feedback from the pressure differences on the top and the bottom surfaces of the structure.

Correlation analysis of upper airway morphology in patients with obstructive sleep apnea and anatomically small retruded mandibles

OBJECTIVE

To investigate the relationship between upper airway morphology and the severity of obstructive sleep apnea (OSA) in patients with anatomically small retruded mandibles.

METHODS

Fifty-two patients with small retruded mandibles underwent polysomnography and airway computed tomography. The airway morphology parameters and sleep assessment were compared between the patients with or without OSA.

RESULTS

Twenty-eight patients diagnosed with OSA, according to polysomnography, had a higher distance between the hyoid bone and mandibular plane (HMP), lateral dimension (LAT)/anteroposterior dimension (AP), but lower minimum cross-sectional area (mCSA), AP, surface area, volume, avgCSA, and airway uniformity (U). The apnea-hypopnea index had negative correlations with mCSA, AP, surface area, volume, avgCSA, and U, and had a positive correlation with HMP and LAT/AP.

CONCLUSION

OSA is common among patients with small retruded mandibles and is associated with a more compressed upper airway shape and longer HMP.

International Consensus Statement on Obstructive Sleep Apnea

BACKGROUND

Evaluation and interpretation of the literature on obstructive sleep apnea (OSA) allows for consolidation and determination of the key factors important for clinical management of the adult OSA patient. Toward this goal, an international collaborative of multidisciplinary experts in sleep apnea evaluation and treatment have produced the International Consensus statement on Obstructive Sleep Apnea (ICS:OSA).

METHODS

Using previously defined methodology, focal topics in OSA were assigned as literature review (LR), evidence-based review (EBR), or evidence-based review with recommendations (EBR-R) formats. Each topic incorporated the available and relevant evidence which was summarized and graded on study quality. Each topic and section underwent iterative review and the ICS:OSA was created and reviewed by all authors for consensus.

RESULTS

The ICS:OSA addresses OSA syndrome definitions, pathophysiology, epidemiology, risk factors for disease, screening methods, diagnostic testing types, multiple treatment modalities, and effects of OSA treatment on multiple OSA-associated comorbidities. Specific focus on outcomes with positive airway pressure (PAP) and surgical treatments were evaluated.

CONCLUSION

This review of the literature consolidates the available knowledge and identifies the limitations of the current evidence on OSA. This effort aims to create a resource for OSA evidence-based practice and identify future research needs. Knowledge gaps and research opportunities include improving the metrics of OSA disease, determining the optimal OSA screening paradigms, developing strategies for PAP adherence and longitudinal care, enhancing selection of PAP alternatives and surgery, understanding health risk outcomes, and translating evidence into individualized approaches to therapy.

The prognostic role of ultrasound and magnetic resonance imaging in obstructive sleep apnoea based on lateral oropharyngeal wall obstruction

PURPOSE

This study examined the prognostic value of the lateral pharyngeal wall (LPW)-based obstruction and obstructive sleep apnoea (OSA) prediction using ultrasound (US) and MRI (magnetic resonance imaging).

METHODS

One hundred patients with and without OSA were enrolled, according to overnight polysomnography. The LPW thickness (LPWT) was measured using a Philips Ingenia 1.5 T MRI device, and US measurements were carried out at rest and during Müller's manoeuvre (MM) with a Samsung RS85 device. The obstruction was localised under drug-induced sleep endoscopy.

RESULTS

Significantly greater LPWT using MRI was observed in the OSA group compared to the control group, while US results showed a significant difference only in the case of LPWT during MM on the left side. Obese patients presented significantly higher LPWT values. A significant correlation between BMI and LPWT was observed. Men presented significantly higher LPWT MRI values and left-sided LPWT using US compared to women. LPWT and AHI parameters were significantly correlated. The severity of LPW obstruction correlated with LPWT, while the LPW collapse significantly correlated with AHI. The severity of LPW collapse differed depending on the AHI values. Using US LPWT values and anthropometric parameters, a 93% effectiveness in OSA prognostication and 89% in LPWT-based obstruction were detected. MRI detected OSA in 90% and LPW-based obstruction in 84%. US successfully detected LPW-based collapse severity in 67%.

CONCLUSION

US LPWT measurements were helpful in detecting OSA and LPWT-based obstruction. These examinations may be useful for surgical planning.

In Situ Investigation of Upper Airway Occlusion in Sleep Disordered Breathing Using Ultrasonic Transducer Arrays

This work presents a novel application of ultrasound for the real-time, non-invasive investigation of occlusion of the upper airway during events of obstructive sleep apnea/hypopnea syndrome. It is hypothesized that ultrasonic pulses applied to the neck during apneic events produce spectral and temporal features that can detect apnea occurrence. Theoretical models of ultrasound propagation and an in vitro test were conducted to test this hypothesis in both transmission and reflection modes. Complete specifications and technical details of the system design and fabrication, which is mounted on each subject's neck, are presented, including the methodology. Nine patients (seven male and two female, mean age of 42 years, with a range of 25 to 56 years, and body mass index 37.6 ± 6.6 kg/m²) were recruited for a full night study, which included simultaneous nocturnal polysomnography for the validation of the results. Nine temporal features and four spectral features were extracted from the envelope of the received pulse waveform. These were used to compute 26 metrics to quantify the changes in the ultrasonic waveforms between normal breathing and apneic events. The statistical analysis of the collected ultrasonic data showed that at least two or more of the proposed features could detect apneic events in all subjects. The findings establish the feasibility of the proposed method as a cost-effective and non-invasive OSAHS screening tool.

Airway morphology and its influence on OSA severity and surgical intervention: a retrospective study

Introduction: The aim was to assess the relationship between airway morphology and surgical intervention in a cohort of patients presenting with increased body mass index (BMI) and a confirmed diagnosis of obstructive sleep apnoea (OSA). A secondary aim was to revisit the relationship between morphology and OSA severity.

Methods: A retrospective analysis was conducted of pre-operative maxillofacial 3D-CT scans of thirty-two patients with a confirmed diagnosis of OSA who received treatment from an ear nose and throat specialist (ENT). Lateral cephalograms were imported into Quick Ceph Studio (Quick Ceph Systems Inc, San Diego, CA, USA) after which linear and angular measurements of selected hard and soft tissues were obtained. 3D-CT images were loaded into the software program 3dMDVultus (3dMD) which permitted 3D visualisation of the airway. Measurements were repeated 3 times on the images of six patients after an interval of two weeks to establish the intraclass correlation coefficient (ICC) for intra-examiner accuracy and reliability. Logistic regression was applied to determine the relationships between morphology, OSA and surgical treatments.

Results: A positive correlation was found between age and the apnoea-hypopnea index (AHI). Morphological measurements of the airway did not exhibit a positive relationship with OSA severity. Posterior airway space at the level of the uvula and tongue, the length of the soft palate and position of the hyoid bone were significantly associated with BMI. No variables were found to be correlated with uvulopalatopharyngoplasty (UPPP) surgery. Notwithstanding, airway length and posterior airway space at the level of the uvula tip were significantly associated with tongue channelling.

Conclusions: Radiographic airway assessment is an invaluable and opportunistic tool for screening OSA but requires judicial use in its prescription and interpretation. There is little correlation between OSA severity and airway morphology and between surgical intervention and morphology. Additional factors need to be considered before a treatment modality is considered and is best managed in a multidisciplinary setting.

Evaluation of oral air space volume in obstructive sleep apnea syndrome using clinical and postmortem CT imaging

OBJECTIVES

Obstructive sleep apnea syndrome (OSAS) induces upper airway occlusion and may cause sudden death during sleep. This study sought to clarify the relationship between oral air space volume and OSAS onset, which is influenced by multiple factors, such as jawbone, dentition morphology, and oral soft-tissue volume.

METHODS

(1) 50 subjects from deceased cases were divided into two groups: OSAS (25 subjects) and controls (25 subjects). (2) 28 subjects from clinical cases were divided into two groups: OSAS (9 subjects) and controls (19 subjects). In all cases, the Computed Tomography (CT) images of the facial region were obtained, and four parameters of oral area volume were analyzed in deceased and clinical cases, and comparisons and analyses were performed between OSAS and control cases. In addition, the efficiency of measurement of these parameters was evaluated using Receiver Operating Characteristic (ROC) curves in OSAS.

RESULTS

(1) In deceased cases, oral soft-tissue volume (OSV), oral air-space volume (OAV), and the ratio of OAV to OSV (%air) showed a significant correlation. (2) In clinical cases, OAV and %air showed a significant correlation. In both postmortem and clinical images, a small %air value indicates a high risk of developing OSAS and a high probability of OSAS-related sudden death.

CONCLUSIONS

It was shown that the %air is an index to evaluate OSAS by CT imaging of the oral region. OSAS may be indicated when the %air value is ≦ 16.0% in deceased cases and ≦ 6.6% in clinical cases.

The correlation between drug-induced sleep endoscopy findings and severity of obstructive sleep apnea

OBJECTIVE

This study aimed to assess the relationship between anthropometric data, drug-induced sleep endoscopy (DISE) findings, and severity of obstructive sleep apnea (OSA).

METHODS

From August 2016 to August 2017, a total of 147 surgically naïve adult patients with OSA underwent DISE. Factors that were analyzed included anthropometric data and DISE findings.

RESULTS

When anthropometric data and DISE findings were analyzed with AHI by univariate analysis, the results showed that Epworth Sleepiness Scale (ESS), body mass index (BMI), neck circumference, concentric collapse of the velum, lateral oropharyngeal collapse, and anterior-posterior collapse of the tongue base were considered potentially independent predictors (p = 0.024, p < 0 .001, p < 0 .001, p < 0.001, p < 0.001, p < 0 .001, respectively, by Spearman correlation). When all important factors were evaluated in a stepwise multiple linear regression analysis, BMI, lateral oropharyngeal collapse, and anterior-posterior collapse of the tongue base were identified as significant predictors for the severity of OSA. The final model was listed as below: AHI score = 2.19 BMI + 7.56 Oropharynx/Lateral degree + 8.23 Tongue base/ Anterior-Posterior degree - 40.59.

CONCLUSION

By analyzing anthropometric data and DISE findings with AHI score, the results indicated that BMI, lateral oropharyngeal collapse, and anterior-posterior collapse of the tongue base were important factors associated with the severity of OSA.

The dorsal and the ventral side of hypoglossal motor nucleus showed different response to chronic intermittent hypoxia in rats

PURPOSE

To study neurochemical reactions to chronic intermittent hypoxia (CIH) in the hypoglossal nucleus (HN) of rats.

METHODS

Adult male Sprague-Dawley rats (n = 12) were randomly divided into two groups (the CIH and the control group). The CIH rats were housed in a hypoxic chamber with the fraction of oxygen volume alternating between 21% and 5% by providing air for 60 s and then providing nitrogen for 60 s from 8:30 am to 16:30 pm each day for 35 days. The control group was housed in a cabin with normal oxygen levels. We studied the expression of c-fos protein, 5-hydroxytryptamine (5-HT) positive terminals, and its 2A receptors in hypoglossal nuclei by immunohistochemistry.

RESULTS

The expression of c-fos, 5-HT positive terminals, and accordingly 5-HT 2A receptors in the CIH group were significantly higher than that in the controls (p < 0.05). The ventral side of the HN showed a clearly higher expression of 5-HT and its 2A receptors than the dorsal side (p < 0.05).

CONCLUSION

There were 2 responses of the HN to CIH. First, CIH induced a higher expression of 5-HT positive terminals and its 2A receptors, and second, this reaction was much more evident in ventral side than in the dorsal side. We postulate that these responses may serve to be a protective and compensatory mechanism for CIH.

Numerical and Experimental Analysis of Inhalation Airflow Dynamics in a Human Pharyngeal Airway

This paper presents a computational and experimental study of steady inhalation in a realistic human pharyngeal airway model. To investigate the intricate fluid dynamics inside the pharyngeal airway, the numerical predicted flow patterns are compared with in vitro measurements using Particle Image Velocimetry (PIV) approach. A structured mesh with 1.4 million cells is used with a laminar constant flow rate of 10 L/min. PIV measurements are taken in three sagittal planes which showed flow acceleration after the pharynx bend with high velocities in the posterior pharyngeal wall. Computed velocity profiles are compared with the measurements which showed generally good agreements with over-predicted velocity distributions on the anterior wall side. Secondary flow patterns on cross-sectional slices in the transverse plane revealed vortices posterior of pharynx and a pair of secondary flow vortexes due to the abrupt cross-sectional area increase. Finally, pressure and flow resistance analysis demonstrate that greatest pressure occurs in the superior half of the airway and maximum in-plane pressure variation is observed at the velo-oropharynx junction, which expects to induce a high tendency of airway collapse during inhalation. This study provides insights of the complex fluid dynamics in human pharyngeal airway and can contribute to a reliable approach to assess the probability of flow-induced airway collapse and improve the treatment of obstructive sleep apnea.

Sonographic Assessment of Oropharynx Movement During Deep Breathing

To investigate the feasibility of ultrasonography in detecting the oropharynx movement during deep breathing and to quantitatively analyze oropharynx airway lumen changes during deep breathing. The motions of oropharynx were monitored, and sonographic measurements of airway lumen were obtained during deep breathing in 448 healthy volunteers. Adequate visualization of oropharynx movement was obtained on all healthy volunteers. The anterior-posterior (AP) diameters and AP/transverse (T) diameter ratios were greater at the end of deep inspiration than that at the end of deep expiration for each sex (p < 0.01). The anterior-posterior dimensional changes were greater than lateral airway dimensional changes each sex (p < 0.05). Ultrasonography could provide realistic impression of the process on the oropharynx movement during deep breathing and perform the quantitative analysis of the oropharynx airway lumen changes during deep breathing. The results were encouraging and supported the utility of ultrasonography in future studies.

High-Resolution Pulse Oximetry and Titration of a Mandibular Advancement Device for Obstructive Sleep Apnea

Background: To determine whether utilizing high-resolution pulse oximetry is a viable method for evaluating the successful titration of oral appliances for the treatment of obstructive sleep apnea (OSA) patients.

Methods: Of 136 consecutive potentially eligible OSA patients, 133 were fitted with mandibular advancement devices (MADs), and 101 completed all phases of treatment. The vertical and horizontal dimensions of the appliances were adjusted based on three-nights with a high-resolution pulse oximeter during sleep and associated software after each adjustment.

Results: Significant improvements in OSA severity were apparent in patients at all disease severity levels. High-resolution pulse oximetry provided reliable guidance in the titration process of mandibular advancement therapy. In 67 subjects (66.3%), a respiratory event index of <5 events/hour was achieved.

Conclusions: OSA can be effectively treated with a MAD at any severity level, and high-resolution pulse oximetry provides critical information to guide oral appliance titration.

Obstructive sleep apnea in patients with laryngeal cancer after supracricoid or vertical partial laryngectomy

Objective

To investigate whether partial laryngectomy is a risk factor for obstructive sleep apnea (OSA) and the effect of different partial laryngectomy methods on OSA.

Method

A prospective study was carried out involving 40 patients who underwent supracricoid partial laryngectomy (SCPL) (24) or vertical partial laryngectomy (VPL) (16) for carcinoma of the larynx. Apnea-hypopnea index (AHI) and oxygen saturation determined by polysomnography (PSG), Epworth sleepiness scale (ESS) score, and body mass index (BMI) were evaluated in patients before surgery, on the day of tracheal tube removal and three months later. In patients who developed apnea, laryngoscopy, Muller’s test, computer tomography (CT) and dynamic sleep magnetic resonance imaging (MRI) were performed to assess the location of airway stenosis and collapse.

Results

The AHI (P<0.001) increased and the lowest oxygen saturation (P<0.001), ESS score (P<0.001) and BMI (P=0.017) decreased after extubation compared with before surgery. Three months after extubation, the same changes were found in AHI (P<0.001) and the lowest oxygen saturation (P<0.001), but the ESS score (P<0.001) increased compared with that preoperatively. The AHI in the SCPL group was significantly higher than that in the VPL group post-operatively (P=0.010), while the miniSpO2 in the SCPL group was lower than that of the VPL group (P=0.022). Laryngoscopy showed that the patients with partial excision of the larynx had a narrowed retropalatal and retrolingual space post-operatively. Muller's test showed the collapse of the retropalatal and retrolingual space, and the CT scan showed that the tongue root was positioned lower in the SCPL group. Compared with the retropalatal and retrolingual space in the expiratory phase according to dynamic sleep MRI, the space in the inspiratory phase was clearly decreased.

Conclusion

Laryngeal function preservation surgery for laryngeal cancer results in the occurrence of OSA by altering the anatomical structure of the larynx and pharynx. OSA was more severe in patients undergoing SCPL than in patients undergoing VPL. The effect of partial laryngectomy on OSA may be related to the surgical method used.

Sagittal Measurement of Tongue Movement During Respiration: Comparison Between Ultrasonography and Magnetic Resonance Imaging

The tongue makes up the anterior pharyngeal wall and is critical for airway patency. Magnetic resonance imaging (MRI) is commonly used to study pharyngeal muscle function in pharyngeal disorders such as obstructive sleep apnoea. Tagged MRI and ultrasound studies have separately revealed ∼1 mm of anterior tongue movement during inspiration in healthy patients, but these modalities have not been directly compared. In the study described here, agreement between ultrasound and MRI in measuring regional tongue displacement in 21 healthy patients and 21 patients with obstructive sleep apnoea was evaluated. We found good consistency and agreement between the two techniques, with an intra-class correlation coefficient of 0.79 (95% confidence interval: 0.75-0.82) for anteroposterior tongue motion during inspiration. Ultrasound measurements of posterior tongue displacement were 0.24 ± 0.64 mm greater than MRI measurements (95% limits of agreement: 1.03 to -1.49). This may reflect the higher spatial and temporal resolution of the ultrasound technique. This study confirms that ultrasound is a suitable method for quantifying inspiratory tongue movement.

Craniofacial and upper airway profile assessment in North Indian patients with obstructive sleep apnea

Introduction

Upper airway imaging can often identify the anatomical risk factors for sleep apnea and provide sufficient insight into the pathophysiology of obstructive sleep apnea (OSA).

Materials and Methods

We conducted a case-control, observational study at a tertiary care hospital in North India. All cases and controls underwent lateral cephalometry and magnetic resonance imaging (MRI) for craniofacial and upper airway evaluation. Only the cases had polysomnography testing for confirmation of OSA and assessing the severity of disease.

Results

Forty cases and an equal number of matched controls were recruited. On X-ray cephalometry, it was observed that the cases had a significantly larger hyoid mandibular distance and soft palate length; and shorter mandibular length. The MRI cephalometric variables were significantly different, the soft palate length, tongue length, and submental fat were longer while the retropalatal and retroglossal distance was shorter amongst the cases. A statistically significant positive correlation was found between the cephalometric parameters and the indices of severity of OSA. An increased hyoid mandibular distance and soft palate length, and a decrease in the lower anterior facial height were found to be predictive of severe OSA (Apnea-Hypopnea Index ->30/h). An increased hyoid mandibular distance, soft palate length, and the tongue length and a reduced mandibular length were found to be predictive of need for continuous positive airway pressure (CPAP) pressures of ≥15 cm H₂O. There were significant differences between the cephalometric parameters of the Indian OSA patients and patients from other ethnicities reported in the literature.

Conclusions

OSA patients had a significantly smaller upper airway compared to age-, sex-, and body mass index-matched controls and cephalometric variables correlated with the indices of OSA severity. The cephalometric assessment was also predictive of severe OSA and the need for higher pressures of CPAP. This indicates the important role of upper airway anatomy in the pathogenesis of OSA.

Prediction of tongue obstruction observed from drug induced sleep computed tomography by cephalometric parameters

OBJECTIVE

To elucidate potential role of cephalometric measurements to predict tongue base obstruction as observed on drug Induced Sleep Computed Tomography (DIS-CT).

METHODS

Study included 35 patients with moderate to severe sleep apnea who underwent DIS-CT & cephalometric examination to assess tongue base obstruction.

RESULTS

Statistically significant difference was noted for SNA angle & Mandibular posterior airway space (PAS) among groups with total tongue obstruction versus Non-total tongue obstruction identified on DIS-CT.

CONCLUSION

Lateral cephalogram can be used as a standard screening tool with commonly used skeletal and soft tissue parameters to predict the possibility of tongue collapse/obstruction during sleep in patient with moderate to severe OSAS.

Pharyngeal airspace of asthmatic individuals and those suffering from obstructive sleep apnea syndrome: Study by CBCT

PURPOSE

The objective of the present study was to comparatively evaluate the oropharyngeal space of patients with obstructive sleep apnea syndrome (OSA) and asthma by means of Cone Beam Computed Tomography (CBCT) images.

MATERIAL AND METHODS

The study included individuals with OSA and asthma (n=10), with OSA and without asthma (n=6), asthmatics without OSA (n=6) and healthy individuals (n=25). All patients were evaluated by a pneumologist and submitted to a nocturnal polysomnogram. Participants underwent CBCT examinations using an I-CAT^® device (Imaging Sciences International, Hatfield, PA, U.S.A.) and all images were exported to Dolphin Image 3D^® software. Cephalometric measurements were taken, as well as measurements of length (C), volume (VOL), sagittal area (SA) and minimum cross-sectional area (MCA); an evaluation was made of the format and contour of the upper airway in three dimensions, with p<0.05 considered significant.

RESULTS

In the results of the present study, a statistically significant difference was found between VOL, SA and MCA (p=0.011; p=0.009; p=0.010) with reduced elevated values among the OSA+Asthma, OSA, Asthma and Control groups. Significant differences were seen between the linear (AP), cross-sectional (TR) and mean transverse area (TA) measurements in the group of patients with OSA and asthma as compared to the control group. In the control group, the greatest narrowing of the airway was observed either in the retroglossal or retropalatal area, while more patients in the experimental groups showed narrowing in the retropalatal area.

CONCLUSION

The condition of OSA+asthma was associated with a substantial reduction in upper airway measurements in comparison to controls.

The structural changes of pharyngeal airway contributing to snoring after orthognathic surgery in skeletal class III patients

BACKGROUND

Two-jaw surgery including mandibular and maxillary backward movement procedures are commonly performed to correct class III malocclusion. Bimaxillary surgery can reposition the maxillofacial bone together with soft tissue, such as the soft palate and the tongue base. We analyzed changes of pharyngeal airway narrowing to ascertain clinical correlations with the prevalence of snoring after two-jaw surgery.

METHODS

A prospective clinical study was designed including a survey on snoring and three-dimensional (3D) computed tomography (CT) in class III malocclusion subjects before and after bimaxillary surgery. We conducted an analysis on changes of the posterior pharyngeal space find out clinical correlations with the prevalence of snoring.

RESULTS

Among 67 subjects, 12 subjects complained about snoring 5 weeks after the surgical correction, and examining the 12 subjects after 6 months, 6 patients complained about the snoring. The current findings demonstrated the attenuation of the largest transverse width (LTW), anteroposterior length (APL), and cross-sectional area (CSA) following bimaxillary surgery given to class III malocclusion patients, particularly at the retropalatal level. The average distance of maxillary posterior movements were measured to be relatively higher (horizontal distance 3.9 mm, vertical distance 2.6 mm) in case of new snorers.

CONCLUSIONS

This study found that bimaxillary surgery could lead to the narrowing of upper airway at the retropalatal or retroglossal level as well as triggering snoring in subjects with class III malocclusion. Based on the current clinical findings, we also found that upper airway narrowing at retropalatal level may contribute to increasing the probability of snoring and that polysonography may need to be performed before orthognathic surgery in subjects with class III malocclusion.

Assessment of tongue mechanical properties using different contraction tasks

Inadequate upper airway (UA) dilator muscle function may play an important role in the pathophysiology of obstructive sleep apnea (OSA). To date, tongue mechanical properties have been assessed mainly using protrusion protocol with conflicting results. Performance during elevation tasks among patients with OSA remains unknown. This study aimed at assessing tongue muscle strength, strength stability, endurance time, fatigue indices, and total muscle work, using elevation and protrusion tasks with repetitive isometric fatiguing contractions in 12 normal plus mild, 17 moderate, and 11 severe patients with OSA, and to assess the influence of body mass index (BMI) and age. Endurance time was longer in protrusion than elevation task (P = 0.01). In both tasks, endurance time was negatively correlated with baseline value of strength coefficient of variation (P < 0.01). Compared with other groups, patients with moderate OSA had the lowest total muscle work for protrusion (P = 0.01) and shortest endurance time (P = 0.04), regardless of the type of task. Additionally, in patients with moderate-severe OSA, the total muscle work for both tasks was lower in nonobese compared with obese (P < 0.05). Total muscle work for protrusion was positively correlated with apnea hypopnea index (AHI) in obese subjects (P < 0.01). Endurance time was shorter (P < 0.01) and recovery time longer (P = 0.02) in the old compared with young subjects. In conclusion, the tongue is more prone to fatigue during the elevation task and in patients with moderate OSA. Obesity appeared to prevent alteration of tongue mechanical properties in patients with OSA. Baseline strength stability and endurance were related, illustrating the role of central neuromuscular output in tongue resistance to fatigue.NEW & NOTEWORTHY To our knowledge, this is the first study to assess and compare tongue function using both elevation and protrusion tasks with repetitive isometric fatiguing contractions in subjects with different OSA status. Tongue mechanical performance seemed to differ between protrusion and elevation tasks and depend on the severity of OSA.

Velopharyngeal mucosal surface topography in healthy subjects and subjects with obstructive sleep apnea

Macroscopic pharyngeal anatomical abnormalities are thought to contribute to the pathogenesis of upper airway (UA) obstruction in obstructive sleep apnea (OSA). Microscopic changes in the UA mucosal lining of OSA subjects are reported; however, the impact of these changes on UA mucosal surface topography is unknown. This study aimed to 1) develop methodology to measure UA mucosal surface topography, and 2) compare findings from healthy and OSA subjects. Ten healthy and eleven OSA subjects were studied. Awake, gated (end expiration), head and neck position controlled magnetic resonance images (MRIs) of the velopharynx (VP) were obtained. VP mucosal surfaces were segmented from axial images, and three-dimensional VP mucosal surface models were constructed. Curvature analysis of the models was used to study the VP mucosal surface topography. Principal, mean, and Gaussian curvatures were used to define surface shape composition and surface roughness of the VP mucosal surface models. Significant differences were found in the surface shape composition, with more saddle/spherical and less flat/cylindrical shapes in OSA than healthy VP mucosal surface models (P < 0.01). OSA VP mucosal surface models were also found to have more mucosal surface roughness (P < 0.0001) than healthy VP mucosal surface models. Our novel methodology was utilized to model the VP mucosal surface of OSA and healthy subjects. OSA subjects were found to have different VP mucosal surface topography, composed of increased irregular shapes and increased roughness. We speculate increased irregularity in VP mucosal surface may increase pharyngeal collapsibility as a consequence of friction-related pressure loss.NEW & NOTEWORTHY A new methodology was used to model the upper airway mucosal surface topography from magnetic resonance images of patients with obstructive sleep apnea and healthy adults. Curvature analysis was used to analyze the topography of the models, and a new metric was derived to describe the mucosal surface roughness. Increased roughness was found in the obstructive sleep apnea vs. healthy group, but further research is required to determine the functional effects of the measured difference on upper airway airflow mechanics.

Evaluation of the oropharynx in class I and II skeletal patterns by CBCT

PURPOSE

This study aimed to evaluate the dimensions of the oropharynx and its shape in the minimum cross-sectional area, in individuals with Class I and Class II skeletal patterns, using three-dimensional CBCT images.

METHODS

Forty-two cone-beam computed tomography images of grown individuals were evaluated. The images were divided according to the patient's skeletal patterns. The dimensions of the oropharyngeal airway space were determined using the Dolphin Imaging software.

RESULTS

The volume and the minimum cross-sectional area were greater in patients with a Class I skeletal pattern, with a median difference of 5379 mm³ and 86.8 mm², respectively. The anteroposterior and lateral diameters in the minimum cross-sectional area were also higher in Class I individuals (2.3 and 6.0 mm, respectively), but the ratio between them was not different.

CONCLUSIONS

The volume and the minimum cross-sectional area of the oropharynx, as well as the anteroposterior and lateral diameters, are lower in individuals with a class II skeletal pattern than in individuals with a class I skeletal pattern. There was no difference in the shape of the oropharynx in healthy individuals with different skeletal patterns.

Three-dimensional analyses of palatal morphology and its relation to upper airway area in obstructive sleep apnea

OBJECTIVE

To evaluate the relationship between palatal morphology and pharyngeal airway morphology in patients who have obstructive sleep apnea (OSA) and compare with a nonsnoring and nonapneic control group.

MATERIALS AND METHODS

Three-dimensional maxillary dental cast measurements from 25 OSA patients (6 women, 19 men) with a mean age of 41.5 (4.8) years, and 25 control group participants (14 women, 11 men) without any symptom of OSA with a mean age of 38.3 (3.7) were correlated with an analysis of pharyngeal area evaluated with lateral cephalograms. Intermolar and intercanine widths and palatal volumes were calculated on the dental casts, and the upper airway area measurements were performed on lateral cephalograms.

RESULTS

OSA patients had smaller oropharyngeal volume and upper airway when compared with controls (P < .001). Palatal area measurements were significantly smaller in OSA (P < .001). OSA patients had significantly narrower maxilla with smaller intermolar and intercanine widths (P < .001). A positive correlation was found between the palatal morphology and pharyngeal dimensions.

CONCLUSIONS

A significant correlation exists between palatal morphology and pharyngeal airway.

Distraction osteogenesis as a treatment of obstructive sleep apnea syndrome: A systematic review

BACKGROUND

To conduct a systematic review to answer the clinical question "What are the effectiveness of mandibular distraction osteogenesis (MDO) and its complications to treat patients with obstructive sleep apnea syndrome (OSAS)?".

METHODS

A systematic search including a computer search with specific keywords, reference list search, and manual search were done. Relevant articles on MDO were assessed and selected in 3 rounds for final review based on 5 predefined inclusion criteria and followed by a round of critical appraisal. Different types of distraction and their treatment outcomes of OSAS were recorded with standardized form and analyzed.

RESULTS

Twelve articles were included in the final review. A total of 256 patients aged 7 days to 60 years were treated with either external or internal MDO, with a mean follow-up period of 6 to 37 months. The average distraction distance of 12 to 29 mm was achieved with various distraction protocols. The success rate for adult patients was 100%, and cure rates were ranged from 82% to 100%. The definition of success or cure for OSAS in children or infants was not defined. Therefore, there were no clearly reported success or cure rates for children/infants in the included studies. However, all studies reported that these patients showed significant improvement in OSAS, with many of them who avoided tracheostomy or had the tracheostomy decannulated. The complication rates were ranged from 0% to 21.4%, with most being from local wound infections or neurosensory disturbances.

CONCLUSION

This systematic review showed that MDO was effective in resolving OSAS in adults with retrognathic mandible. MDO also showed promising results in infants or children with OSAS. From the results of this systematic review, we recommend to define the criteria of success or cure for OSAS surgery in children and infants. We also recommend setting up randomized controlled trials to compare MDO with traditional maxillomandibular advancement surgery for OSAS patients and to provide a better evidence on the success and complication rates of the techniques.

Dimensional and volumetric analysis of the oropharyngeal region in obstructive sleep apnea patients: A cone beam computed tomography study

BACKGROUND

Obstructive Sleep Apnea (OSA) is a potentially life-threatening condition in which there is a periodic cessation of breathing (for 10 sec or longer) that occurs during sleep in the presence of inspiratory effort. The aim of the study was to assess volumetric and dimensional differences between OSA patients and normal individuals in the upright posture.

MATERIAL AND METHOD

The present study was conducted on CBCT scans of 32 patients who were divided into two groups -Group I (control group) and Group II (OSA subjects). Group I consisted of 16 patients with normal airway with ESS score from 2 to 10, STOP BANG Questionnaire score of <3 and who had undergone CBCT for various diagnostic reasons. Group II had patients with ESS score >10, STOP BANG Questionnaire score of > 3, AHI index >5. Linear and angular parameters, volume and minimum cross-section area (MCA) of oropharyngeal airway, anteroposterior length and lateral width at MCA was compared amongst the groups.

RESULTS

The oropharyngeal volume, MCA, and the anteroposterior and lateral width of the airway at MCA of the OSA subjects was significantly lesser than that of normal subjects. The length of both soft palate and tongue was significantly more in Group II. The angle between the nasopharyngeal airway and the oropharyngeal airway was significantly more obtuse in Group II.

CONCLUSION

The reduction in oropharyngeal volume in OSA patients could be attributed to different anatomical and pathophysiological factors that were corroborated with the findings of the present study.

Supra-Epiglottic Upper Airway Volume in Elderly Patients with Obstructive Sleep Apnea Hypopnea Syndrome

Objective

Small upper airway measurements areas and high body mass index are recognized risk factors for obstructive sleep apnea syndrome (OSAS) in non-elderly populations; however, there is limited information regarding elderly patients. We evaluated whether upper airway volume is associated with OSAS and OSAS treated with continuous positive airway pressure (CPAP) treatment and whether BMI is correlated with upper airway volume and measurements in elderly subjects.

Methods

In 60 volunteers aged 75.58±0.9 years: 20 OSAS, 20 OSAS chronically treated with CPAP, and 20 controls, semi-automatic segmentation, retropalatal distance and transverse diameter of the supra-epiglottic upper airway were evaluated using 3DT1-weighted magnetic resonance imaging. Anteroposterior to transverse diameter ratio was defined as retropalatar diameter/transverse diameter.

Results

There were no significant differences in supra-epiglottic upper airway volume between OSAS, CPAP treated patients, and controls. There were significant differences in retropalatal distance and anteroposterior to transverse diameter ratio between OSAS, CPAP treated patients, and controls (P = 0.008 and P<0.0001 respectively). There was a significant correlation between body mass index and retropalatal distance (P<0.05) but not with supra-epiglottic upper airway volume.

Conclusion

In elderly subjects, OSAS and body mass index are not associated with changes in supra-epiglottic upper airway volume but are associated with modification of pharynx shape.

Hypervolemia and Sleep Apnea in Kidney Disease

In end-stage renal disease (ESRD) and heart failure, conditions characterized by fluid overload, both obstructive sleep apnea (OSA) and central sleep apnea (CSA) are highly prevalent. This observation suggests that fluid overload may be a unifying mechanism in the pathogenesis of both OSA and CSA in these conditions. An overnight rostral fluid shift from the legs to the neck and lungs has been shown to contribute to the pathogenesis of OSA and CSA, respectively, in various different patient populations. This article reviews the evidence that supports a role for fluid overload and overnight fluid shift in the pathogenesis of sleep apnea in ESRD. The diagnosis, epidemiology, and clinical features of sleep apnea in patients with ESRD also are considered.

[The syndrome of increased upper airways resistance: What are the clinical features and diagnostic procedures?]

The upper airway resistance syndrome "UARS" is a poorly defined entity, often described as a moderate variant of the obstructive sleep apnea syndrome. It is associated with respiratory effort-related arousal, absence of obstructive sleep apnea, and absence of significant desaturation. It is a relatively common condition that predominantly affects non-obese young adults, with no predominance in either sex. The degree of upper airway collapsibility during sleep of patients with UARS is intermediate between that of normal subjects and that of patients with mild-to-moderate sleep apnea syndrome. Craniofacial and palatal abnormalities are often noted. Patients frequently complain of a functional somatic syndrome, especially daytime sleepiness and chronic fatigue. Polysomnography with esophageal pressure measurements remains the gold standard diagnostic test. The absence of any neurological abnormality gives UARS a good prognosis and it is potentially reversible if treated early. However, some studies suggest that untreated UARS has an increased risk of arterial hypertension. It can also evolve into obstructive sleep apnea.

Lateral teleradiography of the head as a diagnostic tool used to predict obstructive sleep apnea

OBJECTIVES

To (1) assess the relationship between obstructive sleep apnea (OSA) and craniofacial, pharyngeal anatomy and (2) to submit the recommendations for clinicians for increasing the sensitivity in the diagnostics of OSA.

METHODS

A review of the relevant literature linking OSA in adults with cephalometric analysis was performed. In total, 11 articles with similar procedural criteria were selected. The data were analysed using the Comprehensive Meta-Analysis Software (Biostat Inc., Englewood, NJ) and Statistica 12.0 (StatSoft Inc., Dell Software, Tulsa, OK).

RESULTS

Adults with OSA did not show statistically significant differences in the sagittal and vertical skeletal planes in comparison with the controls (p > 0.05). The patients with OSA had soft palate length, width and area increased accordingly by 4.21, 1.99 mm and 0.86 cm(2), tongue area increased by 2.02 cm(2), the upper posterior pharyngeal space (SPAS) and lower posterior pharyngeal space reduced accordingly by 4.53 and 1.32 mm, mandibular plane to the hyoid bone (MP-H) distance increased by 4.14 mm compared with the controls (p < 0.05). The SPAS parameter of the patients with OSA did not show statistically significant differences between the studies, with the mean value being 5.69 mm.

CONCLUSIONS

Analysed cephalometric data totally supported the concept of soft-tissue abnormalities in subjects with OSA, skeletal-only halfway; MP-H and SPAS being the most reliable parameters. Increased MP-H may serve as a predictor when differentiating normal subjects and patients with OSA. Reduced SPAS width could be a prognostic parameter for suspecting OSA. These two values should be kept in mind by dentists and can also be used as a simple auxiliary method by physicians; nevertheless, it is still underestimated and more studies are needed.

Cephalometric norms for the upper airway in a healthy North Indian population

Objective:

The aim was to obtain normative data for cephalometric measurements of the upper airway in the North Indian population.

Design:

Observational study. Setting: University department and teaching hospital out-patient clinic.

Subjects and Methods:

A total of 180 healthy patients were included out of which 90 were males (age range, 8-16 years), and 90 were females (age range, 8-16 years), with normal skeletal facial profile, no history of snoring, sleep apnea, upper airway disease, tonsillectomy or adenoidectomy, obesity, or pathology in the pharynx. Twenty cephalometric airway measurements, including size of the tongue, soft palate, nasopharynx, oropharynx, hypopharynx, and relative position of the hyoid bone and valleculae were obtained. Landmarks on cephalometric radiographs were digitized and measurements were made using a specially designed computer program. Error analysis of measurements was performed and comparison of measurements according to sex was made.

Results:

Significant sex dimorphism was seen for the majority of measurements, with the exception of minimal depth of the airway, oropharyngeal depth of the airway, and the soft palate angle with the hard palate.

Conclusion:

A minimum sagittal dimension of the upper airway was evident despite differences in measurements between sexes. Findings from this study should be a useful reference for the assessment of sleep apnea in the North Indian population.

Heart Failure and Sleep Apnea

Obstructive and central sleep apnea are far more common in heart failure patients than in the general population and their presence might contribute to the progression of heart failure by exposing the heart to intermittent hypoxia, increased preload and afterload, sympathetic nervous system activation, and vascular endothelial dysfunction. There is now substantial evidence that supports a role for fluid overload and nocturnal rostral fluid shift from the legs as unifying mechanisms in the pathogenesis of obstructive and central sleep apnea in heart failure patients, such that the predominant type of sleep apnea is related to the relative distribution of fluid from the leg to the neck and chest. Despite advances in therapies for heart failure, mortality rates remain high. Accordingly, the identification and treatment of sleep apnea in patients with heart failure might offer a novel therapeutic target to modulate this increased risk. In heart failure patients with obstructive or central sleep apnea, continuous positive airway pressure has been shown to improve cardiovascular function in short-term trials but this has not translated to improved mortality or reduced hospital admissions in long-term randomized trials. Other forms of positive airway pressure such as adaptive servoventilation have shown promising results in terms of attenuation of sleep apnea and improvement in cardiovascular function in short-term trials. Large scale, randomized trials are required to determine whether treating sleep apnea with various interventions can reduce morbidity and mortality.

Non-apneic snoring and the orthodontist: radiographic pharyngeal dimension changes with supine posture and mandibular protrusion

OBJECTIVE

To evaluate the radiographic changes that occur in the pharynx and surrounding structures with alteration of posture from the upright to the supine position and the effect that mandibular protrusion whilst supine has on these dimensions.

DESIGN

Prospective cephalometric study.

SETTING

University Dental Hospital and School.

SUBJECTS AND METHOD

This prospective study involved 35 consecutively referred adults with proven non-apneic snoring. Lateral skull radiographs were obtained with the subjects upright in occlusion, supine in occlusion and supine with the mandible protruded to the maximum comfortable position. Radiographs were traced and digitized, and the pharyngeal dimensional changes and hyoid position were examined. Males and females were examined separately.

RESULTS

Radiographic pharyngeal dimensions were changed with altered posture, resulting in significant reductions in the minimum post-palatal (p<0.01) and post-lingual (p<0.05) airway measurements in the supine position. Mandibular protrusion whilst in the supine position produced increases in the functioning space for the tongue.

CONCLUSION

A supine posture results in significant reductions in pharyngeal airway measurements of non-apneic snorers. Mandibular protrusion whilst in the supine position produces an increase in the functioning space for the tongue.

Linear and volumetric airway changes after maxillomandibular advancement for obstructive sleep apnea

PURPOSE

Maxillomandibular advancement (MMA) surgery is a well-established treatment of obstructive sleep apnea (OSA). Although many studies have assessed the efficacy of MMA in treating OSA, very few studies have quantified the magnitude of its changes to airway morphology. Therefore, the present study investigated the linear and volumetric morphologic changes that occur in the pharyngeal airway after treatment of OSA using MMA.

MATERIALS AND METHODS

A retrospective cohort study of patients with OSA treated from May 2010 to February 2014 was performed. Each patient underwent preoperative clinical and fiberoptic nasopharyngoscopic examinations. Pre- and postoperative polysomnograms, lateral cephalograms, and cone-beam computed tomography scans were acquired. The radiographic images were used to determine the linear and volumetric airway measurements. The time and magnitude of skeletal movement were used as the independent variables. The dependent variables included assessment of success or cure, apnea hypopnea index (AHI), cephalometric changes, Epworth score, rapid eye movement sleep, body mass index, and various airway morphologic parameters.

RESULTS

A total of 15 patients (13 men and 2 women) participated in the present study. The surgical success and cure rate was 73.33% and 40.00%, respectively. Statistically significant improvements were found in the airway total volume, minimal cross-sectional area, anteroposterior and lateral dimensions, airway index, airway length, posterior airway space morphology, AHI, and Epworth sleepiness score.

CONCLUSIONS

MMA is a highly successful surgical treatment of OSA that improves airway morphology and sleep quality. MMA results in a shorter and broader airway and associated improvements in the AHI.

Velopharyngeal anatomy in patients with obstructive sleep apnea versus normal subjects

PURPOSE

Obesity can cause disturbed breathing and is one of the most significant risk factors for obstructive sleep apnea (OSA). However, the anatomic basis of OSA and, specifically, the anatomic mechanisms leading from obesity to OSA are still unclear. We examined the anatomic features of the velopharynx in patients with OSA versus those without in correlation with the body mass index (BMI), age, history of snoring, and OSA severity and re-evaluated the contribution of adding a frontal view to the cephalometric analysis of patients with OSA.

MATERIALS AND METHODS

Lateral and frontal cephalometric measurements were taken to assess the velopharyngeal anatomic features of 306 men with various degrees of OSA and 64 men without OSA and without a history of snoring. The demographic, polysomnographic, and cephalometric features were compared.

RESULTS

The patients with OSA had an increased pharyngeal length, thicker velum, a thicker posterior pharyngeal wall, a reduced pharyngeal width, and a consequent narrowing of the pharyngeal lumen. As the BMI increased, the OSA severity increased. Also, in parallel, the velum and posterior pharyngeal wall thickness increased and the pharyngeal width decreased. Three types of velopharyngeal narrowing, with an increased occurrence in severe degrees of OSA, were identified: bottle shape, hourglass shape, and tube shape. These aerodynamically unfavorable changes might cause increased upper airway resistance, explaining the development of both OSA and hypoventilation syndrome in obese patients.

CONCLUSIONS

Velopharyngeal thickening and lumen narrowing were shown to be features of obese men with OSA. However, these features developed only above a threshold BMI value. The combination of frontal and lateral cephalometry is important for comprehensive evaluation of patients with OSA.

Obstructive sleep apnea

Obstructive sleep apnea (OSA) is a common disorder characterized by repetitive collapse of the pharyngeal airway during sleep. Control of pharyngeal patency is a complex process relating primarily to basic anatomy and the activity of many pharyngeal dilator muscles. The control of these muscles is regulated by a number of processes including respiratory drive, negative pressure reflexes, and state (sleep) effects. In general, patients with OSA have an anatomically small airway the patency of which is maintained during wakefulness by reflex-driven augmented dilator muscle activation. At sleep onset, muscle activity falls, thereby compromising the upper airway. However, recent data suggest that the mechanism of OSA differs substantially among patients, with variable contributions from several physiologic characteristics including, among others: level of upper airway dilator muscle activation required to open the airway, increase in chemical drive required to recruit the pharyngeal muscles, chemical control loop gain, and arousal threshold. Thus, the cause of sleep apnea likely varies substantially between patients. Other physiologic mechanisms likely contributing to OSA pathogenesis include falling lung volume during sleep, shifts in blood volume from peripheral tissues to the neck, and airway edema. Apnea severity may progress over time, likely due to weight gain, muscle/nerve injury, aging effects on airway anatomy/collapsibility, and changes in ventilatory control stability.

Analysis of obstruction site in obstructive sleep apnea syndrome patients by drug induced sleep endoscopy

PURPOSE

We analyzed site, pattern and degree of obstruction in Korean male obstructive sleep apnea syndrome (OSAS) patients by drug-induced sleep endoscopy (DISE). We also investigated possible links between BMI, AHI and DISE findings.

MATERIALS AND METHODS

Sixty-nine male patients underwent DISE. DISE findings were reported using our classification system in which modified 'VOTE classification' - obstruction type, site of obstruction, degree of obstruction and anatomical site contributing obstruction - was reported. Associations were analyzed among the results of the polysomnography, patients' characteristics and DISE finding.

RESULTS

Multilevel airway obstruction was found in 84.06% of patients and 15.94% had a unilevel obstruction. Among those with unilevel obstruction, 90.90% had retropalatal level obstruction and 9.10% had retrolingual level obstruction. Palate with lateral pharyngeal wall obstruction (49.28%) is the most common obstruction type of the retropalatal level and tongue with lateral pharyngeal wall (37.68%) is the most common obstruction type of the retrolingual level. Examining the relation between obstruction site according to body mass index (BMI) and severity of OSAS (apnea hypopnea index, AHI), the lateral pharyngeal wall had an increasing tendency associated with higher BMI and higher AHI. But the lateral pharyngeal wall of both levels was statistically significant associated with higher AHI.

CONCLUSION

The majority of the Korean male OSAS patients have multilevel obstruction and according to BMI and AHI, the DISE findings indicate that the lateral pharyngeal wall is the most important anatomical site contributing to obstruction regardless of the level at which the obstruction lies.

Pharyngeal airway dimensions: a cephalometric, growth-study-based analysis of physiological variations in children aged 6-17

OBJECTIVE

The aim was to assess pharyngeal airway dimensions and physiological changes based on lateral cephalometric radiographs from healthy untreated children aged 6-17 years.

MATERIALS/METHODS

The sample consisted of 880 lateral cephalograms (412 females and 468 males) of the Zurich Craniofacial Growth Study. Statistical analyses on cephalometric measurements of airway dimensions (distances 'p': shortest distance between soft palate and posterior pharyngeal wall and 't': shortest distance between tongue and posterior pharyngeal wall) and craniofacial parameters were performed. To disclose differences between different age groups, a Kruskal-Wallis test was applied. The influence of gender on 'p' and 't' was analysed by a Mann-Whitney U-test for each age group separately. The Spearman correlation was computed in order to investigate associations between craniofacial parameters. Variables associated with 'p' and 't' were chosen for multiple regression model investigation.

RESULTS

The results demonstrated high interindividual variations. A slight influence of age on 'p' (P = 0.034) could be attested (+1.03 mm) but not on 't' (P = 0.208). With the exception of the 9-year age group, no significant differences between the genders were found. Correlation analysis revealed several statistically significant correlations between 't' or 'p' and antero-posterior cephalometric variables. All correlation coefficients were, however, very low and the adjusted coefficient of determination also revealed the regression model to be very weak.

CONCLUSIONS

The high interindividual variations of 'p' and 't' render the use of reference values problematic. Contrary to other craniofacial structures, neither age-related changes nor sexual dimorphism were found for 'p' and 't'. Any associations to antero-posterior cephalometric characteristics seem low.

Comparison of cone-beam computed tomography incidental findings between patients with moderate/severe obstructive sleep apnea and mild obstructive sleep apnea/healthy patients

OBJECTIVE

The objective of this study was to compare the incidental radiographic findings in the maxillofacial structures and the pharyngeal airway between subjects with moderate/severe obstructive sleep apnea (OSA) and mild OSA/healthy subjects using cone-beam computed tomography (CBCT) scans.

STUDY DESIGN

A total of 53 subjects with moderate/severe OSA (with a Respiratory Disturbance Index [RDI] ≥ 15 events/h) and 33 mild OSA/healthy subjects (RDI < 15), based on ambulatory somnographic assessment, were recruited. Supine CBCTs were taken and sent for radiological report. The incidental findings were compared between the 2 groups.

RESULTS

Moderate/severe subjects had larger prevalence of conchae bullosa, hypertrophic turbinates, hypertrophic tonsils, elongated or posteriorly placed soft palate, narrower airway, enlarged tongue, and focal calcifications, although no significant differences were found.

CONCLUSIONS

CBCT is useful in identifying maxillofacial and airway anomalies that could interfere with normal breathing; however, no significant difference was found in prevalence of incidental findings between subjects with moderate/severe OSA and mild OSA/healthy subjects. Further studies are necessary to generalize our results.