Effect of titrated mandibular advancement and jaw opening on the upper airway in nonapneic men: a magnetic resonance imaging and cephalometric study

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 role of oral appliance therapy in obstructive sleep apnoea

There is now widespread recognition within the world of sleep medicine of the increasing importance of dental sleep medicine and, in particular, the role of oral appliance therapy (OAT) in the management of adults with obstructive sleep apnoea (OSA). For the purpose of this review, the term OAT refers to a custom-made intra-oral appliance, which acts to posture the mandible in a forward and downward direction, away from its natural resting position. Whilst nasally applied continuous positive airway pressure remains the "gold standard" in nonsurgical OSA management, OAT remains the recognised alternative treatment.This review of OAT aims to provide an evidence-based update on our current understanding of their mode of action, exploring the potential anatomical and physiological impact of their use in preventing collapse of the upper airway; the current clinical practice guidelines, including the recently published National Institute of Clinical Excellence 2021 guidance, in conjunction with the American Academy of Sleep Medicine and American Academy of Dental Sleep Medicine; optimal design features, comparing the role of custom-made versus noncustom OAT devices and the importance of titration in achieving a dose-dependent effect; patient predictors, preference and adherence to OAT; its impact on a range of both patient- and clinician-centred health outcomes, with a comparison with CPAP; the limitations and side-effects of providing OAT; and, finally, a look at future considerations to help optimise the delivery and outcomes of OAT.

Impact of occlusal reconstruction positions on airway dimensions in patients with edentulism and long centric occlusion

OBJECTIVE

To study the airway changes of edentulous patients with a magnitude of long centric (MLC) ≥ 1.5 mm during occlusal reconstruction at the centric relation position (CRP) and muscular position (MP).

METHODS

The CRP and MP were determined by Gothic arch. The cephalometric analysis was taken at the two occlusal positions. The sagittal distance of each part of the upper airway was measured. The differences between two occlusal positions were compared. The difference values were calculated by subtracting the two. The correlation between the MLC and the difference value was analyzed.

RESULTS

The sagittal diameters of palatopharynx and glossopharynx airway at MP were statistically larger than those at CRP (P < 0.05). The MLC had a strong correlation with the ANB angle (r = 0.745, P < 0.001).

CONCLUSION

Compared with the occlusal position of CRP, occlusion reconstruction at MP can provide better airway condition for edentulous patients with large MLC.

Equal effect of a noncustom vs a custom mandibular advancement device in treatment of obstructive sleep apnea

STUDY OBJECTIVES

Numerous types of mandibular advancement devices (MADs) are available to treat patients with obstructive sleep apnea, varying from noncustom to custom devices. Only a limited number of studies have been performed to determine whether a noncustom MAD could be used to predict treatment success of a custom MAD. In this study, we investigated the potential of a new-generation noncustom MAD, by comparing its effectiveness with a custom MAD. We hypothesized that the effectiveness of the devices is similar with regard to both objective (polysomnography) and self-reported (questionnaires, adherence, and patient satisfaction) outcomes.

METHODS

This was a single-center prospective randomized crossover study including a consecutive series of patients with obstructive sleep apnea. Patients were randomized to start either with the noncustom or custom MAD. Both MADs were applied for 12 weeks, followed by polysomnography with MAD in situ and questionnaires. After the first 12 weeks of follow-up, a washout period of 1 week was applied. Equal effectiveness was defined as no significant differences in both objective and self-reported outcomes between both devices.

RESULTS

Fifty-eight patients were included; 40 completed the full follow-up. The median apnea-hypopnea index significantly decreased from 16.3 (7.7, 24.8) events/h to 10.7 (5.6, 16.6) events/h with the custom MAD (P = .010) and to 7.8 (2.9, 16.1) events/h with the noncustom MAD (P < .001). Self-reported outcomes significantly improved in both groups. No significant differences were found between both devices.

CONCLUSIONS

The effectiveness of a noncustom and custom MAD is comparable, which suggests that a noncustom MAD can be used as a selection tool for MAD treatment eligibility to improve MAD treatment outcome.

CLINICAL TRIAL REGISTRATION

Registry: Netherlands Trial Register; Name: The Use of a Boil and Bite Mandibular Advancement Device vs a Custom Mandibular Advancement Device in Obstructive Sleep Apnea Management; URL: https://www.trialregister.nl/trial/7249; Identifier: NL64738.100.18.

CITATION

Bosschieter PFN, Uniken Venema JAM, Vonk PE, et al. Equal effect of a noncustom vs a custom mandibular advancement device in treatment of obstructive sleep apnea. J Clin Sleep Med. 2022;18(9):2155-2165.

Effects of Wearing a 50% Lower Jaw Advancement Splint on Biophysical and Perceptual Responses at Low to Severe Running Intensities

Acute ergogenic effects of wearing occlusal splints have been reported for aerobic and anaerobic exercises, but the literature centered on performance improvement by using jaw repositioning splints is scarce. We aimed to analyze the effect of wearing a 50% lower jaw advancement splint on biophysical and perceptual responses at low to severe running intensities. Sixteen middle- and long-distance runners performed twice a 7 × 800 m intermittent running protocol (with 1 km·h⁻¹ increments and 30 s rest periods) in an outdoor track field using two lower intraoral splints (a placebo and a lower jaw advancer). These devices were custom manufactured for each participant and a randomized and repeated measure design was used to compare conditions. No differences between placebo and lower jaw advancer were found (e.g., 52.1 ± 9.9 vs. 53.9 ± 10.7 mL·kg⁻¹·min⁻¹ of oxygen uptake, 3.30 ± 0.44 vs. 3.29 ± 0.43 m of stride length and 16 ± 3 vs. 16 ± 2 Borg scores), but small effects were sometimes observed (e.g., 109.2 ± 22.5 vs. 112.7 ± 25.2 L·min⁻¹ of ventilation, ES = −0.42). Therefore, this jaw advancement splint had no substantial ergogenic effect on biophysical and perceptual responses when running at different intensities.

Correlation between Polysomnographic Parameters and Tridimensional Changes in the Upper Airway of Obstructive Sleep Apnea Patients Treated with Mandibular Advancement Devices

BACKGROUND

The effectiveness of mandibular advancement devices has been solidly demonstrated in the past. They are considered a valid alternative treatment to continuous positive airway pressure for patients with obstructive sleep apnea. Nevertheless, the relationship between polysomnographic parameters and the increase in the volume of the upper airway in patients with obstructive sleep apnea syndrome has not been clearly established so far. This study aimed to determine the impact of these oral appliances upon the volume of the airway after the device titration phase and correlate it with the degree of mandibular advancement and the improvement of polysomnographic parameters.

METHODS

All patients were diagnosed by polysomnography and were treated with a customized, titratable mandibular advancement device. Three-dimensional volumetric measurements were performed using cone beam computed tomography.

RESULTS

The present study included 45 patients diagnosed with obstructive sleep apnea hypopnea syndrome (mild in 23 patients, moderate in 11 and severe in 11). Forty-four percent of the patients presented with an apnea hypopnea index <5/h at the end of treatment. The volume of the upper airway increased an average of 4.3 ± 5.9 cm3, this represents a percentage increase of 20.9%, which was significantly correlated with an apnea hypopnea index and a minimum oxygen saturation improvement.

CONCLUSIONS

The mandibular advancement device used was found to be effective in improving polysomnographic parameters. Moreover, the oral appliance was able to significantly increase the tridimensional dimensions of the upper airway. Moreover, this finding was correlated with a reduction in the apnea hypopnea index (p = 0.007) and an increase on minimum oxygen saturation (p = 0.033).

The effect of gradually increased mandibular advancement on the efficacy of an oral appliance in the treatment of obstructive sleep apnea

STUDY OBJECTIVES

To analyze the effect of gradual increments of mandibular advancement on the treatment efficacy of mandibular advancement devices and identify determinants of effective and target protrusion for OSA.

METHODS

Patients were prospectively recruited. The mandible was titrated from 0 mm with a stepwise increment of 0.5 mm until the AHI was reduced to the lowest level. Rhinospirometry, rhinomanometry, and magnetic resonance imaging were used to observe the change of respiratory function and upper airway morphology.

RESULTS

Forty-two patients aged 41.5 ± 9.0 years participated. There was a dose-dependent relationship between mandibular protrusion and the AHI improvement rate, the success rate, and the normalization rate; the changing curves plateaued after approximately 70% of maximal mandibular protrusion was achieved. The correlation between AHI and mandibular protrusion became stronger as the severity of OSA increased. The target protrusion for patients with mild, moderate, and severe OSA was 3.5 ± 1.8 mm (38.6 ± 19.4% maximal mandibular protrusion), 5.8 ± 1.9 mm (62.9 ± 18.8% maximal mandibular protrusion), and 5.9 ± 2.2 mm (68.8 ± 15.6% maximal mandibular protrusion), respectively. Regression analysis revealed that the factors influencing effective and target protrusion included change of maximal lateral dimension of the total upper airway with mandibular advancement devices, mean lateral dimension of the oropharynx, and soft palate length. Further protrusion brought more lateral expansion of the velopharynx, whereas the change in nasal ventilation was not significant.

CONCLUSIONS

The dose-dependent effect of mandibular protrusion on reduction of AHI by mandibular advancement devices was nonlinear and became more pronounced with increased severity of OSA. The mandibular protrusion should be more personalized to each patient.

CLINICAL TRIAL REGISTRATION

Registry: Chinese Clinical Trial Registry; Name: Study of the Onset Point of Oral Appliance Treatment in Obstructive Sleep Apnea and Hypopnea Syndrome; URL: http://www.chictr.org.cn/showproj.aspx?proj=22291; Identifier: ChiCTR-IND-17013232.

Effects of dental implant treatment on sleep quality in edentulous older people: A prospective cohort study

Background

Edentulism and sleep disturbances are commonly seen among older people and cause serious negative effects on their daily lives. Edentulism can induce sleep problems by changing maxillo-mandibular anatomy and surrounding soft tissues. The effect of the treatment of complete edentulism on sleep disturbances is not sufficiently understood. The purpose of this cohort study is to detect how different treatment options affect sleep quality, daytime fatigue and sleep disorder breathing in totally edentulous elderly people.

Material and Methods

Ninety-six individulas (50 male and 46 female) participated in this prospective cohort study. The patients were non-randomly assigned to three groups, fixed implant-supported prostheses (FP), removable implant-supported prostheses (RP) and conventional total prostheses (CP). The Pittsburgh Sleep Quality Index (PSQI), the Epworth Sleepiness Scale (ESS) and the STOP-Bang questionnaire were calculated before (T0) and one year after (T1) their prosthetic rehabilitations.

Results

Although there was no statistically significant difference between groups in terms of mean PSQI (p=0.524), ESS (p=0.410) and STOP-Bang (p=0.697) scores at T0, there was a significant difference between groups in terms of mean PSQI (p=0.011), ESS (p=0.030) and STOP-Bang (p=0.024) scores at T1. The FP group, when compared to CP group was associated with significantly better scores in the PSQI (Δ = -3.399, 95% CI= -4.612 to -2.187), ESS (Δ = -1.663, 95% CI= -3.149 to -0.176) and STOP-Bang (Δ = -0.994, 95% CI= -1.592 to -0.397).

Conclusions

Within the limitations of this study FP was associated with a positive influence on sleep disturbances. Randomized controlled trials will be needed to provide reliable inference on this association.

Key words:Dental implant, edentulism, older people, sleep disturbances.

Ready-made versus custom-made mandibular advancement appliances in obstructive sleep apnea: A systematic review and meta-analysis

Mandibular advancement appliances (MAAs) are an increasingly accepted treatment choice in obstructive sleep apnea management. The ready-made MAAs has questioned the need for a customised MAAs, given the former is more accessible and considerably cheaper. We conducted a systematic review and meta-analysis to evaluate both objective and patient-centred outcomes in relation to ready-made and custom-made MAAs s. Biomedical electronic databases, clinical trials registers and Grey literature were searched to January 2017, for randomised controlled trials. Meta-analyses of clinical trials were conducted for a range of objective (apnea-hypopnea index, treatment response) and subjective scales (daytime sleepiness; quality of life; patient preference and adherence). The review included three randomised controlled trials, which revealed low risk of bias. Custom-made MAAs s achieved a significant mean difference in the apnea-hypopnea index (-3.2; 95% confidence interval -5.18, -1.22; p = .004), daytime sleepiness (-0.98; 95% confidence interval -1.97, 0.01; p = .05), observed mean difference in Functional Outcomes of Sleep Questionnaire scores (0.76; 95% confidence interval 0.14, 1.38; p = .02), self-reported adherence (6.4-7 nights per week and 5-6.3 hr per night) and expressed preference (p ≤ .001) when compared with the ready-made MAAs s. Custom-made MAAs s offer clear definable advantages, demonstrating significant clinical effectiveness, patient preference and adherence.

An update on mandibular advancement devices for the treatment of obstructive sleep apnoea hypopnoea syndrome

Continuous positive airway pressure (CPAP) remains the gold standard treatment for obstructive sleep apnoea hypopnoea syndrome (OSAHS). However, the high efficacy of CPAP is offset by intolerance and poor compliance, which can undermine effectiveness. This means that alternatives to CPAP are also necessary. In recent years, oral appliances have emerged as the leading alternative to CPAP. There is now a strong body of evidence supporting their use in OSAHS and clinical guidelines now recommend their use in mild OSAHS and in more severe cases when CPAP fails. These devices are by no means a homogenous group as they differ greatly in both design and action. The most commonly used appliances are mandibular advancement devices (MAD) that increase airway diameter with soft tissue displacement achieved by mandibular protrusion. Despite the growing evidence, there are still barriers to MAD provision. Their effectiveness can be difficult to predict and there is debate about the required level of design sophistication. These uncertainties prevent more widespread inclusion of MAD within clinical sleep services. This review will focus on the efficacy, effectiveness, design features, side-effects of and patient selection for MAD therapy. Comparison will also be made between MAD and CPAP therapy.

Ready-Made Versus Custom-Made Mandibular Repositioning Devices in Sleep Apnea: A Randomized Clinical Trial

STUDY OBJECTIVES

To compare the effectiveness of a custom-made (MRDc) versus ready-made (MRDr) mandibular repositioning devices (MRD) in the management of obstructive sleep apnea (OSA).

METHODS

A randomized crossover trial design was adopted in which patients with a confirmed diagnosis of OSA were randomly allocated to receive either a 3-month period of ready-made or custom-made MRD, with an intervening washout period of 2 weeks, prior to crossover. Treatment outcomes included both objective sleep monitoring and patient-centered measures (daytime sleepiness, partner snoring and quality of life).

RESULTS

Twenty-five patients, with a mild degree of OSA (apnea-hypopnea index of 13.3 [10.9-25] events/h) and daytime sleepiness (Epworth Sleepiness Scale of 11 [6-16]), completed both arms of the trial. The MRDc achieved a complete treatment response in 64% of participants, compared with 24% with the MRDr (p < 0.001). A significant difference was observed in treatment failures, when comparing the MRDr (36%) with the MRDc (4%). Excessive daytime sleepiness (Epworth Sleepiness Scale ≥ 10) persisted in 33% (MRDc) and 66% (MRDr) of OSA subjects, following treatment. A statistically significant improvement was observed in quality of life scales following MRDc therapy only. Significant differences were observed in relation to both the number of nights per week (p = 0.004) and hours per night (p = 0.006) between the two different designs of device.

CONCLUSIONS

The study demonstrates the significant clinical effectiveness of a custom-made mandibular repositioning device, particularly in terms of patient compliance and tolerance, in the treatment of OSA.

The size and behavior of the human upper airway during inhalation of aerosols

INTRODUCTION

The mouth, the pharynx and the larynx are potential sites of aerosol deposition in the upper airway during inhalation of aerosolized drugs. The right angle bend of the lumen at the back of the mouth, the position of the tongue, the variable size and shape of the lumen in the pharynx and the larynx, and the breathing pattern could increase aerosol deposition in the upper airway and decrease lung deposition. Areas covered: In this review, the anatomy of the upper airway from the oral cavity to the glottis and the impact of mandibular protrusion and incisal opening on the size of the upper airway are highlighted. In addition, the impact of inhalation maneuvers, inhaler mouthpiece geometries and a stepped mouthpiece on the size of the upper airway are discussed. Expert opinion: The structure of the upper airway lumen does not have a fixed cross sectional area and is susceptible to both constriction and distension during inhalation. The size of the upper airway can be enlarged through mandibular protrusion and/or incisal opening which might decrease aerosol deposition in the upper airway and increase lung deposition.

Effects of varying mandibular protrusion and degrees of vertical opening on upper airway dimensions in apneic dentate subjects

INTRODUCTION

Despite numerous studies investigating the dimensional and therapeutic effects of mandibular advancement splints (MASs), data regarding the effects of differently designed individual and non-adjustable MASs on the upper airway in fully dentate apneic subjects in the sagittal plane including comparison of these effects with a placebo device are sparse. The present study aimed to determine the dimensional changes in the sagittal plane created by differently designed MASs in the upper airway in fully dentate apneic subjects and to compare these changes with the effects of a placebo device.

MATERIALS AND METHODS

Magnetic resonance (MR) images of 9 dentate apneic subjects with 5 differently designed MASs and without a MAS were obtained. We measured the area of the entire pharynx (velopharynx, oropharynx, hypopharynx) on these MR images and compared the dimensional changes.

RESULTS

The dimensional changes triggered by two specific MASs (75% of the maximum mandibular protrusion with 5 mm vertical opening, and 75% of the maximum mandibular protrusion with 10 mm of vertical opening) in the entire pharynx in the sagittal plane were statistically significant compared to the other MASs (p < 0.05). The MAS effecting 75% of the maximum mandibular protrusion and 10 mm of vertical opening created a significant dimensional increase only in the velopharyngeal area among the three pharyngeal sites (p ≤ 0.003).

CONCLUSION

While the degree of mandibular protrusion created by the MAS affects the dimensions of the upper airway, the degree of the vertical opening exerts no significant dimensional effect in the sagittal plane in fully dentate apneic patients. The mandibular protrusion effect is comparatively larger in the velopharyngeal region.

An animal model of obstructive sleep apnoea-hypopnea syndrome corrected by mandibular advancement device

OBJECTIVE

The aim of the study is to establish a stable animal model of obstructive sleep apnoea-hypopnea syndrome (OSAHS) and assess the effectiveness of a mandibular advancement device (MAD).

MATERIALS AND METHODS

Eighteen 6-month-old male New Zealand white rabbits were randomized into three groups according to intervention: Group OSAHS, Group MAD, and a control group (n = 6 for each group). Rabbits in Group OSAHS and Group MAD were established as OSAHS model by injection, at a dose of 2 ml hydrophilic polyacrylamide gel, in the submucous muscular layer of the soft palate. Computed tomography (CT) and polysomnography (PSG) showed that OSAHS was developed successfully, the rabbits in Group MAD were fitted with the MAD and CT of the upper airway and PSG evaluated its effectiveness. Histological observation of the injection sites was conducted.

RESULTS

CT scans showed the reduced sagittal space and cross-sectional areas of retropalatal upper airway in Group OSAHS were corrected by MAD (upper airway space in Group MAD was similar to that in the control group). The rabbits in Group OSAHS developed obvious sleep apnoea and hypopnea in supine position, with increased apnoea-hypopnea index and decreased oxygen saturation (SaO2). These were significantly improved by MAD and apnoea and hypopnea were not observed. Histology of the soft palate showed that the injected gel was entirely surrounded with connective tissues.

CONCLUSION

We primarily developed an OSAHS and MAD therapy animal model with narrow oropharynx in upper airway which could be further available for OSAHS analysis.

Clinical guidelines for oral appliance therapy in the treatment of snoring and obstructive sleep apnoea

The purpose of this review is to provide guidelines for the use of oral appliances (OAs) for the treatment of snoring and obstructive sleep apnoea (OSA) in Australia. A review of the scientific literature up to June 2012 regarding the clinical use of OAs in the treatment of snoring and OSA was undertaken by a dental and medical sleep specialists team consisting of respiratory sleep physicians, an otolaryngologist, orthodontist, oral and maxillofacial surgeon and an oral medicine specialist. The recommendations are based on the most recent evidence from studies obtained from peer reviewed literature. Oral appliances can be an effective therapeutic option for the treatment of snoring and OSA across a broad range of disease severity. However, the response to therapy is variable. While a significant proportion of subjects have a near complete control of the apnoea and snoring when using an OA, a significant proportion do not respond, and others show a partial response. Measurements of baseline and treatment success should ideally be undertaken. A coordinated team approach between medical practitioner and dentist should be fostered to enhance treatment outcomes. Ongoing patient follow-up to monitor treatment efficacy, OA comfort and side effects are cardinal to long-term treatment success and OA compliance.

Tongue and lateral upper airway movement with mandibular advancement

STUDY OBJECTIVES

To characterize tongue and lateral upper airway movement and to image tongue deformation during mandibular advancement.

DESIGN

Dynamic imaging study of a wide range of apnea hypopnea index (AHI), body mass index (BMI) subjects.

SETTING

Not-for-profit research institute.

PARTICIPANTS

30 subjects (aged 31-69 y, AHI 0-75 events/h, BMI 17-39 kg/m(2)).

INTERVENTIONS

Subjects were imaged using dynamic tagged magnetic resonance imaging during mandibular advancement. Tissue displacements were quantified with the harmonic phase technique.

MEASUREMENTS AND RESULTS

Mean mandibular advancement was 5.6 ± 1.8 mm (mean ± standard deviation). This produced movement through a connection from the ramus of the mandible to the pharyngeal lateral walls in all subjects. In the sagittal plane, 3 patterns of posterior tongue deformation were seen with mandibular advancement-(A) en bloc anterior movement, (B) anterior movement of the oropharyngeal region, and (C) minimal anterior movement. Subjects with lower AHI were more likely to have en bloc movement (P = 0.04) than minimal movement. Antero-posterior elongation of the tongue increased with AHI (R = 0.461, P = 0.01). Mean anterior displacements of the posterior nasopharyngeal and oropharyngeal regions of the tongue were 20% ± 13% and 31% ± 17% of mandibular advancement. The posterior tongue compressed 1.1 ± 2.2 mm supero-inferiorly.

CONCLUSIONS

Mandibular advancement has two mechanisms of action which increase airway size. In subjects with low AHI, the entire tongue moves forward. Mandibular advancement also produces lateral airway expansion via a direct connection between the lateral walls and the ramus of the mandible.

CITATION

Brown EC; Cheng S; McKenzie DK; Butler JE; Gandevia SC; Bilston LE. Tongue and lateral upper airway movement with mandibular advancement. SLEEP 2013;36(3):397-404.

Effects of mandibular advancement on upper airway dimension and collapsibility in patients with obstructive sleep apnea using dynamic upper airway imaging during sleep

OBJECTIVES

The objective of this study was to evaluate the effects of mandibular advancement on oropharyngeal dimension and collapsibility and reveal the predominate site of change produced by mandibular advancement in patients with obstructive sleep apnea (OSA).

STUDY DESIGN

Sixteen adults (13 males and 3 females) with symptomatic mild to severe OSA participated. Custom-made silicone mandibular positioners were used to keep the mandible at 67% of maximum advancement. Changes in the oropharyngeal size and collapsibility with mandibular advancement were evaluated using ultrafast computed tomography taken during wakefulness and midazolam-induced sleep. Cross-sectional areas were assessed using electron beam tomography at 4 levels: high retropalatal (HRP), low retropalatal (LRP), high retroglossal (HRG), and low retroglossal (LRG).

RESULTS

During sleep, the minimum cross-sectional areas decreased 36.5%, 67.8%, 75.5%, and 65.8% at each level of HRP, LRP, HRG, and LRG respectively, as compared with those measured during wakefulness. Mandibular advancement during sleep increased 75.7%, 141.3%, 128.1%, and 119.9% at each level. The oropharynx showed 70.3%, 110.4%, 140.3%, and 156.9% increase in the Collapsibility Indices during sleep at each level of HRP, LRP, HRG, and LRG, respectively, compared with wakefulness. However, collapsibility indices decreased 29.1%, 23.2%, 21.4%, and 34.1% at each level with mandibular advancement.

CONCLUSION

Mandibular advancement increases oropharyngeal diameter and decreases oropharyngeal collapsibility during midazolam-induced sleep respiration at the retropalatal as well as the retroglossal region in most patients with OSA.

Effect of head posture on pediatric oropharyngeal structures: implications for airway management in infants and children

PURPOSE OF REVIEW

Although head and neck posture has direct effects on the upper airway in infants and children, many of these effects remain unclear or not well established. As airway patency and airway access are critical in sedated and/or unconscious children, recent developments in this area should be made known to pediatric anesthesiologists, intensive care physicians and other emergency caregivers.

RECENT FINDINGS

All recent studies observed large interindividual variability in anatomical measurements, especially in trachea length. More evidence has been gained that lateral position improves upper airway patency in sedated children. Several studies brought indirect information on head posture for laryngoscopy and intubation.

SUMMARY

The site of obstruction of the airway in sedated children in different postures is now more clear. Implications of head flexion and extension in intubated children have been extensively studied, and clinical consequences have been detailed. Due to large interindividual anatomic variability, depth marks set on the tubes by their manufacturers and guidelines regarding calculations of insertion depth should be made with caution in infants and neonates. Despite several studies, there is still little scientific evidence regarding proper head posture for laryngoscopy and intubation.

Effect of oral appliances on genioglossus muscle tonicity seen with diffusion tensor imaging: a pilot study

OBJECTIVE

The purpose of this study was to examine whether the diffusion tensor imaging (DTI) technique can be used as a modality to represent the structural deformation in the in vivo genioglossus (GG) muscle fibers with oral appliances (OAs).

STUDY DESIGN

Three healthy subjects were recruited for the pilot study. A custom-made OA, which is modified from a tongue retaining device (TRD), was constructed for each subject before the DTI acquisitions. Recordings were made with and without OAs to compare the GG muscle fiber deformation.

RESULT

DTI provided good resolution of tongue muscle fibers in vivo and successful isolation of each muscle fiber bundle. In particular, the GG muscle fiber deformation due to OAs was clearly visualized.

CONCLUSIONS

This DTI technique may be used not only to identify the individual myoarchitecture, but also to assess muscle fiber deformations in vivo, such as constriction, dilatation, and rotation with OAs. Clinical studies for OSA patients will be the next step.

The effect of mandibular advancement appliances on awake upper airway and masticatory muscle activity in patients with obstructive sleep apnoea

BACKGROUND

There is little understanding of how dental appliances, designed to posture the mandible forwards, act on pharyngeal airway dilatory and masticatory muscles in patients with obstructive sleep apnoea (OSA). This study evaluates, in a prospective cohort design, the effect of mandibular advancement splints (MAS) on awake genioglossus (GG), geniohyoid (GH) and masseter (M) muscle activity.

METHODS

Fifty OSA patients received a custom-made removable Herbst MAS appliance, adjusted for maximum therapeutic benefit, as judged by subjective improvement. Awake electromyographic (EMG) activity was recorded at baseline and with the MAS in situ, by using bipolar surface electrodes in patients seated upright and in the natural head position. The lower splint was modified to facilitate the placement of the intra-oral bipolar surface electrodes used to record GG EMG activity.

RESULTS

Significant increases in GG (P = 0.041), GH (P<0.001) and M (P<0.001) muscle activity accompanied placement of the MAS.

CONCLUSIONS

These findings support the contention of a physiological role, which may act to augment the anatomical action of MAS.

A pilot study of quantitative assessment of mandible advancement using pressure?flow relationship during midazolam sedation

It has been proposed that a titration of the mandibular positioner would be a promising method for predicting the outcome of nasal continuous positive airway pressure (CPAP) therapy. This study was carried out to test the hypothesis that mandible advancement could be evaluated by analysis of inspiratory flow limitation using a titration procedure. To explore its effect, we examined upper airway pressure-flow relationships using a titrated mandible positioner during midazolam sedation. Non-flow limited inspiration occurred when the mandible was advanced 7.1 +/- 1.2 mm from centric occlusion position. In the centric occlusion position (0 mm advancement), Pcrit was -1.9 +/- 2.9 cmH2O and Rua was 23.3 +/- 4.5 cmH2O L(-1) s(-1). In the eMAP position, Pcrit was -7.3 +/- 1.9 cmH2O and Rua was 27.8 +/- 3.3 cmH2O L(-1) s(-1). Essentially no CPAP was required to overcome flow limitation in eMAP position, whereas 3.7 +/- 2.2 cmH2O CPAP was required in centric occlusion position. We conclude that assessing inspiratory flow limitation using a titrated mandible positioner was effective for estimating individual-matched mandible positions.

Influences of the breathing route on upper airway dynamics properties in normal awake subjects with constant mouth opening

MB (mouth breathing) promotes the occurrence of sleep-disordered breathing even in non-apnoeic subjects. Considering that MO (mouth opening) contributes to an increase in UA (upper airway) collapsibility independently of MB, the aim of the present study was to assess the influence of breathing route on UA dynamics in the presence of MO. Bilateral anterior magnetic phrenic nerve stimulation was performed 2 s after expiratory onset in 12 healthy male subjects during wakefulness (age, 50±5 years; body mass index, 27.8±2.4 kg/m2) during MB through a mouthpiece and during exclusive NB (nasal breathing) with the same mouthpiece in place. Twitch-induced V̇I (instantaneous flow), Pph and Pes (pharyngeal and oesophageal pressures respectively) were recorded and the corresponding resistances were measured. A polynomial regression model, V̇I=k1Pd+k2Pd2, was used to characterize flow–pressure relationship and to determine the Pd value at which UA collapses. There was no difference in UA dynamic properties between NB and MB when UA collapse occurred above the pharyngeal catheter. For twitches where UA collapse occurred lower in the UA, pharyngeal resistance decreased from NB to MB (2.0±0.3 and 1.5±0.2 cmH2O·l−1·s respectively; P=0.02; values are means±S.D.), whereas closing pressure increased (−25.7±10.1 and −18.0±3.0 cmH2O respectively; P=0.04). We conclude that (i) in the presence of MO the dynamic properties of the proximal UA free of phasic activity do not differ between NB and MB, and (ii) MB decreases the upstream resistance and increases collapsibility of the distal UA.

Effect of a non-adjustable oral appliance on upper airway morphology in obstructive sleep apnoea

BACKGROUND

To evaluate the effect of oral appliance (OA) on upper airway morphology and its relationship with treatment response in subjects with obstructive sleep apnoea (OSA).

METHODS

Symptomatic OSA subjects were recruited. Non-adjustable OA was custom made. Variables examined at baseline and while wearing the device at 2 months included polysomnographic data, computed tomographic measurements of upper airway cross sectional area at level of velopharynx (VA) and hypopharynx (HA), upper airway volume, and cephalometric parameters. Treatment outcome was based on post-treatment apnoea-hypopnoea index (AHI).

RESULTS

Forty patients were recruited and 23 (7 women) completed the study. They were middle-aged (49, 40-58 years) (median, interquartile range) and overweight (BMI 26, 23.3-29.5 kg/m2), with moderate OSA (AHI 26.4, 14.1-36). The overall post treatment AHI was 8.4 (2.4-12.5), with 14 (61%) patients showing good response (AHI<10), and the other 9 patients showing moderate response (>50% reduction in AHI but still 10). OA decreased the cross-sectional area of the HA (P=0.046), showed a trend of decreasing the ratio of cross-sectional area of the HA to cross-sectional area of the VA (P=0.053) and significantly increased the overall upper airway volume (P=0.006, n=11). No significant relationship between upper airway parameters and treatment outcome was identified.

CONCLUSIONS

OA altered upper airway morphometry towards a profile consistent with decreased propensity to collapse, which may thus have contributed to improvement of OSA.

Sleep nasendoscopy: a diagnostic tool for predicting treatment success with mandibular advancement splints in obstructive sleep apnoea

This prospective, cohort study evaluated the role of sleep nasendoscopy (SNE) with simultaneous mandibular protrusion in predicting successful mandibular advancement splint (MAS) therapy in subjects with obstructive sleep apnoea (OSA). Nineteen OSA subjects diagnosed by overnight polysomnography were referred for MAS therapy, following SNE investigation. A Herbst MAS was fabricated for each subject. Once this had been adjusted for maximal, subjective, therapeutic effect, follow-up sleep studies were undertaken with the appliance in situ. The SNE was repeated with the appliance in place to allow the effects of the original mandibular protrusion and the actual effect of the MAS to be compared. The MAS was removed and the original and current site(s) of obstruction evaluated. Pre-treatment SNE showed airway obstruction at the following levels: intermittent multi-level (16 subjects), sustained multi-level (two subjects) and tongue base (one subject). In all individuals, gentle advancement of the mandible during SNE improved airway patency and reduced snoring. When the SNE was repeated with the MAS in situ, all subjects showed improvements in snoring and airway patency. Follow-up sleep studies confirmed the efficacy of the MAS, with all patients showing a reduction in the apnoea/hypopnoea index (AHI). Median reductions in AHI (from 28.1 to 6.1, P < 0.001) and Epworth Sleepiness Scale (ESS) scores (from 9 to 6, P < 0.001) were highly statistically significant. The results suggest that SNE with concomitant mandibular advancement to mimic MAS wear, could be a valuable prognostic indicator of successful MAS treatment.

Clinical audit of subjects with snoring & sleep apnoea/hypopnoea syndrome fitted with mandibular repositioning splint

Snoring and obstructive sleep apnoea/hypopnoea syndrome (OSAHS) are often treated with mandibular repositioning splints (MRS), but the efficacy and satisfaction of them has not been comprehensively addressed. A survey on the use of and satisfaction with MRS was posted to 177 patients referred by a hospital orthodontic department for custom-fitting of a MRS. Data were analysed using non-parametric techniques. The response rate was 81% (n=144). Responders (30F, 114M) had mean (SD) age of 51 (11) years, apnoea+hypopnoea index (AHI) of 24 (21) per hr and Epworth Score of 10 (5) at diagnosis, and had been supplied with their MRS a median 7 (IQR 5-11) months previously. Fifty of the 144 patients (35%) had been offered continuous positive airway pressure (CPAP) treatment but had declined or abandoned this. Self-reported MRS use was 5 (2) h/night, with 74 of the 144 patients (51%) continuing to use MRS at least occasionally at a median 7 months after fitting. Survival analysis showed 12% still using MRS at 12 months. Epworth score fell slightly with MRS therapy [-2.4 (3.5); P=0.005] and 7 daytime and 2 nocturnal symptoms improved in MRS users (all P<0.05). Marital satisfaction did not change with MRS. Problems preventing MRS use in 70 non-users included: non-retention (n=12), sore mouth (n=13) or jaw (n=7), difficulties falling asleep (n=10) or breathing (n=7), excessive salivation (n=4), dental damage (n=4) and other problems (n=3). Continued use of MRS therapy was associated with a higher number of teeth, low marital satisfaction perceived by partners and greater improvement in symptoms reported by patients and partners. Continuance with MRS may be low and linked to tolerance problems.