Sleep Breath DOI 10.1007/s11325-014-0994-9


Oral appliance effectively reverses Muller’s maneuver-induced upper airway collapsibility in obstructive sleep apnea and hypopnea syndrome Yanhui Zhao & Huimin Shi & Xiaofeng Lu & Jindong Chen & Ping Nie & Yanmei Tang & Li Tao & Min Zhu

Received: 11 November 2013 / Revised: 22 April 2014 / Accepted: 25 April 2014 # Springer-Verlag Berlin Heidelberg 2014

Abstract Objectives To verify the effects of oral appliance (OA) on upper airway morphology under intraluminal pressure, identify specific sites of upper airway collapsibility that can be reversed by OAs, and determine the relationship between OA efficacy and dynamic upper airway changes using computed tomography (CT) with Muller’s maneuver. Materials and methods Nineteen adult Chinese patients with symptomatic mild-to-moderate sleep apnea were recruited from our sleep center. Each patient was fitted with a twopiece OA. Dynamic changes in the retropalatal and retroglossal airway were evaluated using CT at end-expiration and during Muller’s maneuver, both with and without an OA. Results Upper airway changes in the end-expiration phase before OA placement did not significantly differ from those after OA placement. However, under intraluminal pressure induced by Muller’s maneuver, OA effectively expanded the upper airway at multiple levels. In addition, OA counteracted negative intraluminal pressure more effectively in the retropalatal region than in the retroglossal region, with 95.65,

Y. Zhao : X. Lu : P. Nie : Y. Tang : L. Tao : M. Zhu (*) Department of Oral and Cranio-Maxillofacial Science, Shanghai Ninth People’s Hospital, School of Stomatology, Shanghai Key Laboratory of Stomatology, Shanghai Jiao Tong University School of Medicine, No. 639 Zhi Zao Ju Rd, 200011 Shanghai, China e-mail: [email protected] H. Shi Department of Radiology, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai, China J. Chen Department of Orthodontics, Institute and Hospital of Stomatology, Nanjing University Medicine School, Nanjing Stomatological Hospital, Nanjing, Jiangsu 210008, China

68.75, 72.41, and 78.38 % improvements in the collapsibility index of the anteroposterior dimension, transverse dimension, minimum cross-sectional area, and volume of the retropalatal region, respectively. Both nonresponders and responders to OA treatment were sensitive to the intraluminal pressure induced by Muller’s maneuver. However, the collapsibility of the retropalatal airway improved significantly only in the responders, not in the nonresponders. Conclusions OA effectively treats OSAHS by improving upper airway collapsibility. Keywords Oral appliance . Muller’s maneuver . OSAHS . Polysomnography . Computed tomography

Introduction Obstructive sleep apnea and hypopnea syndrome (OSAHS) is a chronic sleep-related respiratory dysfunction that mainly affects middle-aged people [1–3]. Given the prevalence of undiagnosed OSAHS in the population [2] and the various clinically important co-morbidities associated with OSAHS, the pathogenesis and treatment of sleep apnea are an interdisciplinary challenge [3]. Among the mainstream treatment modalities for obstructive sleep apnea (OSA), oral appliance (OA) is convenient and minimally invasive. OA is recognized as a first-line treatment and is indicated not only in primary snorers with mild-tomoderate OSA but also patients who have severe disease and cannot tolerate continuous positive airway pressure [4, 5]. The detailed mechanism of OA in OSA treatment is complex and not yet fully elucidated. Understanding the potential mechanisms of OA is critical to improve treatment efficacy, increase patient compliance, and select appropriate candidates for OA therapy. Advancement of the mandible by OA effectively activates upper airway dilator muscles [6],

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patients had undergone any treatment at the time of enrollment. Sleep apnea was diagnosed using baseline laboratorybased polysomnography with an apnea–hypopnea index (AHI)≥5 events per hour. Exclusion criteria were severe OSA (AHI>30 events per hour), aggressive periodontitis, severe temporomandibular disorder, loss of multiple molars, severe nasal obstruction, and unstable systemic diseases. Nineteen patients (17 men and 2 women) were enrolled in the study. Their demographic data, including age, sex, height, weight, and neck circumference, were collected. Body mass index was determined as weight (kg)/square of height (m). All participants signed informed consent forms at the beginning of the study. The study protocol was approved by the ethics committee of Shanghai Ninth People’s Hospital.

decreases upper airway collapsibility [7], and even changes airway curvature [8]. However, studies on whether OA expands upper airway dimensions have had inconsistent results [7, 9, 10]. The heterogeneity among studies was attributed to the included populations, methodology designs, sampling sizes, imaging techniques, and OA types. In addition, most of the studies did not analyze the performance of OA under intraluminal pressure, which may have confounded the results. Recently, Tsuiki et al. [11] found that OA reduces neuromuscular compensation during wakefulness and helps regain a normal upper airway configuration. A follow-up study reported a successful case of OA therapy and demonstrated that mandibular advancement with an OA decreased the electromyographic activity of the genioglossus muscle, which was essential to maintain upper airway patency during wakefulness [12]. These findings indicated that the falsenegative rate of the data for the actual performance of an OA in upper airway expansion increases if intraluminal pressure is not considered. Consequently, evaluation of dynamic changes in the upper airway under intraluminal pressure is warranted, for it could more objectively explain the efficacy of OA treatment and the underlying mechanisms. Muller’s maneuver involves maximal inspiration against a closed nose and mouth [13]. The intraluminal pressure induced by Muller’s maneuver could simulate apneic events and upper airway collapsibility during sleep. Fiberoptic nasopharyngoscopy has demonstrated that Muller’s maneuver clears sites of upper airway obstruction and reveals OSA severity [14]; however, some disadvantages limit the value of this approach [13, 15]. In contrast, three-dimensional computed tomography (CT) combined with Muller’s maneuver has great advantages in detecting sites of upper airway collapsibility and dynamic changes in airway caliber and does not impede the performance of Muller’s maneuver. In this study, we used CT combined with Muller’s maneuver to evaluate dynamic changes in the upper airway before and after OA placement. We aimed to (1) determine whether the effects of OA on the upper airway differ under the intraluminal pressure induced by Muller’s maneuver; (2) identify the mechanism of action of OAs and specific sites of upper airway collapsibility; and (3) evaluate the relationship between OA efficacy and dynamic changes in the upper airway under Muller’s maneuver, with and without OAs.

Each patient underwent baseline one-night polysomnography at the sleep center prior to the study for verifying the diagnosis and disease severity. The polysomnography parameters we used have been previously reported [10]. Data on sleep stages, mean and minimum oxygen saturation, and apneic and hypopneic events were recorded. After at least 2 months of treatment, when the OA had been titrated to achieve appropriate mandibular protrusion and when the patient reported no major discomfort, polysomnography was repeated with the OA in place.

Materials and methods

Upper airway CT with Muller’s maneuver


Dynamic upper airway changes were evaluated using a 16 slice volumetric spiral CT (Light Speed Ultra; GE Healthcare, Milwaukee, WI, USA). Prior to CT, a single investigator taught all subjects to perform Muller’s maneuvers before and after OA placement until they could quickly finish the maneuver. Patients were instructed to perform maximal

Adult Chinese patients with symptomatic sleep apnea were recruited from the sleep center of the Department of Oral and Cranio-Maxillofacial Science, Shanghai Ninth People’s Hospital, between January 2011 and June 2012. None of the


OA Each patient was provided with a custom-made two-piece full-coverage OA (Herbst type). Alginate impressions of the maxillary and mandibular dental arches were obtained. Intercuspal occlusion and maximum mandibular protrusion were also recorded using wax registration. Acrylic splints of the OA were constructed to anchor both dental arches and provide full dentition coverage. The upper and lower parts of the appliance were connected with one adjustable screw on each side, to provide gradual titration of the mandible in 0.25mm increments. The initial mandible titration was set at 65 % of the maximum protrusion, and an adjustment was made within the following month according to the comfort level and symptoms of the patient. The vertical opening of the interincisal edges was set at 5 mm to minimize clockwise rotation of the mandible when wearing the OA.

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inspiration against a closed nose and mouth [16]. All subjects underwent radiography while awake and lying in a supine position. The head of the patient was fixed with a rigid head positioner, with the Frankfort horizontal plane perpendicular to the ground. Patients were instructed to practice two actions: (1) tight dental occlusion without swallowing and (2) Muller’s maneuver. CT scanning was performed from the top of the thyroid cartilage to the intra-orbital plane to capture the retropalatal and retroglossal anatomy. The pharyngeal morphology was imaged in two phases: during end-expiration and during Muller’s maneuver. CT was repeated with the OA in place, and again images were obtained during end-expiration and Muller’s maneuver. All four images of each patient were assessed to determine changes in upper airway morphology (Fig. 1). The CT parameters were

120 kV, 200 mA, and 1.25-mm slice thickness. CT was performed by the same experienced radiologist to avoid systematic bias.

Fig. 1 Four image sequences of changes in upper airway morphology at retropalatal minimum CSA in a selected patient. a retropalatal minimum CSA for end-expiration phase. b retropalatal minimum CSA with oral

appliance. c retropalatal minimum CSA during Muller’s maneuver. d retropalatal minimum CSA during Muller’s maneuver with oral appliance

Image analysis CT images were transferred to a commercially available workstation (GE Advantage Workstation version 4.3; GE Healthcare, Milwaukee, WI, USA) for further upper airway multiplanar reconstruction and measurements. In all four image sequences, the minimum cross-sectional areas (CSAs) of the retropalatal and retroglossal regions were measured in the axial and sagittal planes. The retropalatal region was located between the level of the hard palate and the tip of the uvula; the retroglossal region was located between the tip of the

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uvula and the upper edge of the epiglottis. Using electronic calipers, we measured the anteroposterior (AP) dimension, transverse dimension, and minimum CSA of the retropalatal and retroglossal regions. Retropalatal and retroglossal volumes were measured using volume rendering to disarticulate air from soft tissues. To avoid systematic error, each measurement was performed thrice by the same investigator, and the average value was used.

subjects completed the thorough protocol. Comparison with baseline variables showed that OAs reduced the AHI (by 66.24 %; p50 % or to

Oral appliance effectively reverses Muller's maneuver-induced upper airway collapsibility in obstructive sleep apnea and hypopnea syndrome.

To verify the effects of oral appliance (OA) on upper airway morphology under intraluminal pressure, identify specific sites of upper airway collapsib...
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