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Figure.
Lateral cephalometry showing parameters measured. A, The length from anterior nasal spine (ANS) to posterior nasal spine (PNS) was measured. The length of the soft palate was defined as the distance from the posterior nasal spine to the uvula tip; retropalatal space, as the narrowest posterior airway space at the level of the soft palate; and retrolingual space, as the narrowest posterior airway space at the level of the tongue base. B, Angle of mouth opening was measured as the angle defined by a maxillary incisor–to–glenoid fossa line intersecting with a glenoid fossa–to–mandibular incisor line.

Lateral cephalometry showing parameters measured. A, The length from anterior nasal spine (ANS) to posterior nasal spine (PNS) was measured. The length of the soft palate was defined as the distance from the posterior nasal spine to the uvula tip; retropalatal space, as the narrowest posterior airway space at the level of the soft palate; and retrolingual space, as the narrowest posterior airway space at the level of the tongue base. B, Angle of mouth opening was measured as the angle defined by a maxillary incisor–to–glenoid fossa line intersecting with a glenoid fossa–to–mandibular incisor line.

Table 1. 
Comparison of Cephalometric Variables Between Success and Nonsuccess Groups
Comparison of Cephalometric Variables Between Success and Nonsuccess Groups
Table 2. 
Comparison of Sleep Videofluoroscopic Variables Between Success and Nonsuccess Groups Without and With the Application of the MAD
Comparison of Sleep Videofluoroscopic Variables Between Success and Nonsuccess Groups Without and With the Application of the MAD
Table 3. 
Comparison of Sleep Videofluoroscopic Variables Without and With Application of the MAD Between Success and Nonsuccess Groups
Comparison of Sleep Videofluoroscopic Variables Without and With Application of the MAD Between Success and Nonsuccess Groups
1.
American Sleep Disorders Association, Practice parameters for the treatment of snoring and obstructive sleep apnea with oral appliances. Sleep 1995;18 (6) 511- 513
PubMed
2.
Lee  CHMo  JHChoi  IJ  et al.  The mandibular advancement device and patient selection in the treatment of obstructive sleep apnea. Arch Otolaryngol Head Neck Surg 2009;135 (5) 439- 444
PubMedArticle
3.
Suratt  PMDee  PAtkinson  RLArmstrong  PWilhoit  SC Fluoroscopic and computed tomographic features of the pharyngeal airway in obstructive sleep apnea. Am Rev Respir Dis 1983;127 (4) 487- 492
PubMed
4.
Walsh  JKKatsantonis  GPSchweitzer  PKVerde  JNMuehlbach  M Somnofluoroscopy: cineradiographic observation of obstructive sleep apnea. Sleep 1985;8 (3) 294- 297
PubMed
5.
Pepin  JLFerretti  GVeale  D  et al.  Somnofluoroscopy, computed tomography, and cephalometry in the assessment of the airway in obstructive sleep apnoea. Thorax 1992;47 (3) 150- 156
PubMedArticle
6.
Hillarp  BNylander  GRosen  IWickstrom  O Videoradiography of patients with habitual snoring and/or sleep apnea: technical description and presentation of videoradiographic results during sleep concerning occurrence of apnea, type of apnea, and site of obstruction. Acta Radiol 1996;37 (3, pt 1) 307- 314
PubMedArticle
7.
Lee  CHMo  JHKim  BJ  et al.  Evaluation of soft palate changes using sleep videofluoroscopy in patients with obstructive sleep apnea. Arch Otolaryngol Head Neck Surg 2009;135 (2) 168- 172
PubMedArticle
8.
Lee  CHKim  JWLee  HJ  et al.  An investigation of upper airway changes associated with mandibular advancement device using sleep videofluoroscopy in patients with obstructive sleep apnea. Arch Otolaryngol Head Neck Surg 2009;135 (9) 910- 914
PubMedArticle
9.
Sforza  EKrieger  JBacon  WPetiau  CZamagni  MBoudewijns  A Determinants of effective continuous positive airway pressure in obstructive sleep apnea: role of respiratory effort. Am J Respir Crit Care Med 1995;151 (6) 1852- 1856
PubMedArticle
10.
Ng  ATQian  JCistulli  PA Oropharyngeal collapse predicts treatment response with oral appliance therapy in obstructive sleep apnea. Sleep 2006;29 (5) 666- 671
PubMed
11.
Sadaoka  TKakitsuba  NFujiwara  YKanai  RTakahashi  H The value of sleep nasendoscopy in the evaluation of patients with suspected sleep-related breathing disorders. Clin Otolaryngol Allied Sci 1996;21 (6) 485- 489
PubMedArticle
Original Article
July 19, 2010

Determinants of Treatment Outcome After Use of the Mandibular Advancement Device in Patients With Obstructive Sleep Apnea

Author Affiliations

Author Affiliations: Departments of Otorhinolaryngology (Drs C. H. Lee, J.-W. Kim, H. J. Lee, Seo, and D.-Y. Kim), Oral Surgery (Dr Yun), and Psychiatry (Dr Yoon), Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, South Korea; Departments of Otorhinolaryngology (Dr Rhee) and Pharmacology (Dr Park), Seoul National University College of Medicine, Seoul National University Hospital, Seoul, South Korea; and Department of Otorhinolaryngology, Dankook University College of Medicine, Chonan-si, Korea (Dr Mo).

Arch Otolaryngol Head Neck Surg. 2010;136(7):677-681. doi:10.1001/archoto.2010.106
Abstract

Objective  To determine the predictors affecting treatment outcome after application of the mandibular advancement device (MAD).

Design  Retrospective analysis.

Setting  Tertiary care university hospital.

Patients  A total of 76 patients (68 men and 8 women) who were treated with the MAD for obstructive sleep apnea (OSA) were included from September 2005 through August 2008. All the subjects underwent cephalometry, nocturnal polysomnography, and sleep videofluoroscopy (SVF) before and at least 3 months after receipt of a custom-made MAD. Sleep videofluoroscopy was performed before and after sleep induction and was analyzed during 3 states of awakeness, normoxygenation sleep, and desaturation sleep. Subjects were divided into success and nonsuccess groups depending on treatment outcome.

Main Outcome Measures  Multiple variables from cephalometry and SVF including the length of the soft palate, retropalatal space, retrolingual space, and mouth opening angle were evaluated during sleep events with or without the MAD between success and nonsuccess group.

Results  The soft palate was significantly longer in the nonsuccess group than in the success group. The retropalatal and retrolingual airway spaces and mouth opening angle were not different between 2 groups. Application of the MAD increased the retrolingual space and decreased the length of the soft palate and the mouth opening angle significantly in both success and nonsuccess groups. However, retropalatal space was widened only in the success group, which showed that retropalatal space may be important in determining treatment response of the MAD.

Conclusion  The length of the soft palate showed a difference between success and nonsuccess groups, and widening of retropalatal space might be an important factor for successful outcome with MAD application.

At present, the use of the mandibular advancement device (MAD) is increasing because of its convenience and excellent outcomes. The established indication for the MAD was mild to moderate obstructive sleep apnea (OSA), and the MAD was recommended as the first-line therapy for mild OSA and as the second-line therapy for moderate to severe OSA.1 Recently, several authors reported its outstanding outcome even in patients with severe OSA, and we have also reported the success rate of 75% in patients with severe OSA.2

The action mechanism of the MAD for improving OSA has been reported to be the maintenance of the upper airway, not only by increasing retropalatal and retrolingual spaces but also by reducing pharyngeal collapsibility. However, it is not known which factors are involved with successful treatment outcome with application of the MAD.

Sleep videofluoroscopy (SVF) has been introduced as a valuable modality for evaluation of dynamic airway changes quantitatively,36 and we also have reported the efficacy of SVF for evaluation of patients with OSA.7 In the present study, we tried to determine the differences between success and nonsuccess groups after application of the MAD and determinants that may account for treatment outcomes.

METHODS
SUBJECTS

From September 2005 through August 2008, 76 Korean subjects (68 men and 8 women, mean [SD] age, 51.7 [0.3] years [range, 21-69 years]) who visited the Sleep Center at Seoul National University Bundang Hospital, Seongnam, South Korea, were retrospectively included. All the subjects underwent full-night nocturnal polysomnography (PSG) and were diagnosed as having OSA. They had undergone both cephalometry and SVF without MAD application after the first visit. They were referred to 1 dentist, and a custom-made MAD was fabricated for each patient. The MAD was designed as a monobloc that holds the mandible fixed at 60% of maximal protrusion without open bites. Patients had a second full-night PSG, cephalometry, and SVF after at least 3 months with the custom-made MAD applied.

Subjects with previous oropharyngeal surgery were excluded from this study. All subjects had a body mass index lower than 35 (calculated as weight in kilograms divided by height in meters squared). This study was approved by the institutional review board of Seoul National University Bundang Hospital.

ASSESSMENT OF TREATMENT RESULTS

Subjects were divided into success and nonsuccess groups depending on treatment outcome. Success was defined as more than 50% reduction of apnea-hypopnea index (AHI) and a postoperative AHI lower than 20. Those who did not meet these criteria were included in the nonsuccess group.

SLEEP VIDEOFLUOROSCOPY

All the subjects underwent SVF as previously described, with or without the MAD.7 Briefly, in an angiography room subjects were place in a supine position on a C-arm table (Allura Xper FD fluoroscopy; Philips, Eindhoven, the Netherlands), with the head on a pillow. They were instructed to breathe in and out naturally with a physician's guidance. Oxygen saturation was monitored throughout the examination. Fluoroscopic images of lateral view in the head and neck area were recorded for 15 seconds in each of 3 events: awake event, normoxygenation sleep event, and desaturation sleep events.

During the normal respiration before sedation, an awake event was recorded for 15 seconds. Then, subjects were given approximately 0.05 mg/kg of midazolam initially. If patients did not fall asleep after the initial injection, an additional 0.02 mg/kg of midazolam was added to a maximum dose of 0.1 mg/kg. In patients with OSA, after administration of midazolam, oxygen saturation does not drop initially, and after a couple of minutes, patients begin to snore and oxygen saturation begins to decrease. One 15-second normoxygenation sleep event was recorded while oxygen saturation did not change compared with oxygen saturation during wakefulness, and two 15-second desaturation sleep events were recorded when oxygen saturation dropped by 4% or more. A 4% oxygen drop represents a direct result of cessation of airflow and represents a period of apnea or hypopnea. Desaturation sleep event could not be seen in patients without OSA.

EVALUATION OF PARAMETERS OF CEPHALOMETRY AND SVF BETWEEN SUCCESS AND NONSUCCESS GROUPS

Cephalometric parameters such as the length from anterior nasal spine to posterior nasal spine, length of the soft palate, retropalatal space, and retrolingual space were measured and analyzed between success and nonsuccess groups. The length of the soft palate, retropalatal space, retrolingual space, and the angle of mouth opening were measured and evaluated during 3 different events: the awake event and 2 sleep events (normoxygenation sleep event and desaturation sleep event). The length of the soft palate was defined as the distance from the posterior nasal spine to the uvula tip; retropalatal space, as the narrowest posterior airway space at the level of the soft palate; retrolingual space, as the narrowest posterior airway space at the level of the tongue base; and the angle of mouth opening, as the angle formed by a maxillary incisor–to–glenoid fossa line intersecting a glenoid fossa–to–mandibular incisor line (Figure).

STATISTICAL ANALYSIS

The unpaired t test was used to analyze differences among awake or sleep events. The paired t test was used to analyze differences between parameters with or without the MAD. All parametric results were expressed as mean (SD). P < .05 was considered statistically significant for all parameters.

RESULTS
DEMOGRAPHIC DATA

The mean (SD) AHI was 38.9 (19.7) in subjects without the MAD and 12.3 (11.4) in subjects with the MAD. The mean (SD) body mass index (BMI) was 25.6 (2.6), and the lowest oxygen saturation was 79.2% (7.8%) without the MAD and 83.5% (12.2%) with the MAD.

Among 75 patients, 56 met the success criteria and 20 did not. The number of patients with mild, moderate, and severe OSA were 11, 39, and 26, respectively, and the success rate of patients with mild, moderate, and severe OSA were 55%, 77%, and 77%, respectively.

COMPARISON OF CEPHALOMETRIC VARIABLES

When cephalometric variables were compared between success and nonsuccess groups with or without application of the MAD, the length from anterior nasal spine to posterior nasal spine, retropalatal space, and retrolingual space were not different between the 2 groups (Table 1). Only the length of the soft palate showed a marked difference between the 2 groups (P = .005). The mean (SD) length of the soft palate was 42.3 (4.6) mm and 46.2 (5.8) mm in the success and nonsuccess groups without application of the MAD, respectively. With application of the MAD, the mean (SD) length of the soft palate also showed a significant difference between the success (40.4 [3.9] mm) and nonsuccess (46.0 [4.9] mm) groups (P = .001).

COMPARISON OF SLEEP VIDEOFLUOROSCOPIC VARIABLES

Without application of the MAD, retropalatal space, retrolingual space, and mouth opening angle did not show any significant difference between success and nonsuccess groups both during awakeness and sleep events. Only the length of the soft palate showed significant differences during awakeness and desaturation sleep events (P = .002 and .04, respectively), and it was significantly longer in the nonsuccess group without MAD application. During normoxygenation sleep events, it was longer in the nonsuccess group but without statistical significance (P = .17; Table 2).

With the application of a MAD, the length of the soft palate, retropalatal space, and angle of mouth opening showed a marked difference between success and nonsuccess group during desaturation sleep events. The mean (SD) length of the soft palate was 41.7 (6.6) mm in the success group and 46.0 (5.2) mm in the nonsuccess group. The retropalatal spaces were 3.2 (2.6) mm and 1.0 (1.9) mm in the success and nonsuccess groups, respectively, and it was shown that retropalatal space was almost collapsed in the nonsuccess group during desaturation sleep events, whereas retrolingual space was preserved in the nonsuccess group even during desaturation sleep events. While the angle of mouth opening did not increase during sleep events in the success group, it increased significantly during sleep events in the nonsuccess group (P < .005). The angle of mouth opening was significantly greater in the nonsuccess group (P = .003; Table 2).

COMPARISON OF VIDEOFLUOROSCOPIC VARIABLES WITH OR WITHOUT MAD APPLICATION

We have shown in our previous study that the MAD increased retrolingual and retropalatal spaces and decreased the length of the soft palate and mouth opening angle.8 In the success group, the effect of MAD application showed results similar to our previous study. The MAD increased retropalatal and retrolingual space and decreased the length of the soft palate and the mouth opening angle significantly in the success group. However, in the nonsuccess group, although the MAD increased retrolingual space and decreased the length of the soft palate and the mouth opening angle, it did not increase retropalatal space, which is a noteworthy difference between success and nonsuccess groups (P = .88 during desaturation sleep events; Table 3).

COMMENT

This study showed predictors of treatment outcomes with MAD application. We compared several variables of cephalometry and SVF between success and nonsuccess groups and revealed that the length of the soft palate was the most important prognostic factor in predicting the outcome of the MAD.

In cephalometric findings, only the length of the soft palate showed a marked difference between success and nonsuccess groups. The protrusion of the mandible by the MAD is likely to increase the tension around the upper airway, resulting in a decrease in the collapsibility of the upper airway. If patients with OSA have a longer soft palate, it could be assumed that the retropalatal airway might collapse more easily during sleep compared with patients with a shorter soft palate.

The dynamic parameters of SVF also showed similar results with cephalometric findings. The length of the soft palate was different between success and nonsuccess groups: it was longer in nonsuccess group, suggesting that more tension around retropalatal space might be needed to prevent the airway from being collapsed.

In our previous study, we had shown that the length of the soft palate was not different between success and nonsuccess groups (P = .08).2 The previous study had fewer subjects (n = 49) compared with this study (n = 76). The increased number of subjects might explain the increased significance of this study.

We have shown in our previous study that the length of the soft palate is elongated in patients with OSA and correlated with the severity of OSA.7 However, the meaning of the length of the soft palate is not understood completely in the context of OSA. When we assess the surgical outcome of uvulopalatopharyngoplasty in patients with OSA, the length of the soft palate did not affect the surgical outcome (data not shown). Since the elongated soft palate was usually resected in the surgical procedure, the soft palate might not have influenced the surgical outcome.

With regard to continuous positive airway pressure (CPAP) treatment, it was reported that the length of the soft palate affected the level of effective CPAP, showing that more pressure is needed to overcome the collapsibility of the soft palate with a longer soft palate.9 In the case of MAD application, although it was reported that soft palate length showed a significantly greater shortening in responders after treatment, this is the first report, to our knowledge, in which the success group (responders) had a shorter soft palate. Because more CPAP pressure is needed in patients with a longer soft palate, more advancement of the MAD might be needed in patients with a longer soft palate for successful management.

Another finding of this study was that the retropalatal space was wider and not collapsed in the success group with application of the MAD, whereas it was collapsed in the nonsuccess group. This might support the importance of retropalatal space in determining the response to the MAD. Retrolingual space is widened in both the success and nonsuccess groups; however, retropalatal space is widened only in the success group (Table 3). In other words, preservation of the retropalatal airway after application of the MAD might be important in predicting treatment outcome after application of the MAD. One recent study showed similar results, in which oropharyngeal collapse predicts treatment outcome with oral appliance therapy for OSA.10 The study showed that patients with primary oropharyngeal collapse showed good response and those with primary velopharyngeal collapse showed poor response with application of the MAD, suggesting that the MAD could control retrolingual space more effectively than retropalatal space.

Our results provide useful information on revealing differences between success and nonsuccess groups and give some insights on treatment outcome of the MAD. The MAD gives tension to the soft tissue around the upper airway, preventing collapse of the airway space.

This study, however, also has some limitations, and they were discussed in our previous report.7 Briefly, both cephalometry and SVF are superimposed 2-dimensional images of 3-dimensional structures. Therefore, it could not explain lateral movement of the upper airway. In addition, a whole sleep period was not included for SVF and sleep was induced by drug administration, although there was a study proving that drug-induced sleep represents normal sleep.11 In spite of all of those limitations, the present study provided novel information about predictors of treatment outcome of MAD application and a difference in the action mechanism of the MAD between success and nonsuccess group in patients with OSA.

In conclusion, the length of the soft palate was longer in the nonsuccess group compared with the success group, and a longer soft palate might help the retropalatal airway collapse more easily. In those with MAD application, SVF showed the difference between success and nonsuccess groups, in which the retropalatal airway was well preserved in the success group and collapsed in the nonsuccess group.

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Article Information

Correspondence: Ji-Hun Mo, MD, PhD, Department of Otorhinolaryngology, Dankook University College of Medicine, San 16-5 Anseo-dong, Cheonan, Chungcheongnam-do 330-715, South Korea (jihunmo@gmail.com).

Submitted for Publication: September 7, 2009; final revision received January 26, 2010; accepted February 17, 2010.

Author Contributions: Dr Mo had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Drs C. H. Lee and J.-W. Kim contributed equally to this article. Study concept and design: C. H. Lee, J.-W. Kim, Yun, D.-Y. Kim, Yoon, Rhee, Park, and Mo. Acquisition of data: H. J. Lee, Seo, and Mo. Analysis and interpretation of data: Mo. Drafting of the manuscript: H. J. Lee, Seo, Yun, D.-Y. Kim, Yoon, Rhee, and Park. Critical revision of the manuscript for important intellectual content: C. H. Lee, J.-W. Kim, and Mo. Statistical analysis: H. J. Lee, Seo, Yun, D.-Y. Kim, Yoon, and Mo. Administrative, technical, and material support: C. H. Lee, J.-W. Kim, Seo, Rhee, Park, and Mo. Study supervision: Mo.

Financial Disclosure: None reported.

References
1.
American Sleep Disorders Association, Practice parameters for the treatment of snoring and obstructive sleep apnea with oral appliances. Sleep 1995;18 (6) 511- 513
PubMed
2.
Lee  CHMo  JHChoi  IJ  et al.  The mandibular advancement device and patient selection in the treatment of obstructive sleep apnea. Arch Otolaryngol Head Neck Surg 2009;135 (5) 439- 444
PubMedArticle
3.
Suratt  PMDee  PAtkinson  RLArmstrong  PWilhoit  SC Fluoroscopic and computed tomographic features of the pharyngeal airway in obstructive sleep apnea. Am Rev Respir Dis 1983;127 (4) 487- 492
PubMed
4.
Walsh  JKKatsantonis  GPSchweitzer  PKVerde  JNMuehlbach  M Somnofluoroscopy: cineradiographic observation of obstructive sleep apnea. Sleep 1985;8 (3) 294- 297
PubMed
5.
Pepin  JLFerretti  GVeale  D  et al.  Somnofluoroscopy, computed tomography, and cephalometry in the assessment of the airway in obstructive sleep apnoea. Thorax 1992;47 (3) 150- 156
PubMedArticle
6.
Hillarp  BNylander  GRosen  IWickstrom  O Videoradiography of patients with habitual snoring and/or sleep apnea: technical description and presentation of videoradiographic results during sleep concerning occurrence of apnea, type of apnea, and site of obstruction. Acta Radiol 1996;37 (3, pt 1) 307- 314
PubMedArticle
7.
Lee  CHMo  JHKim  BJ  et al.  Evaluation of soft palate changes using sleep videofluoroscopy in patients with obstructive sleep apnea. Arch Otolaryngol Head Neck Surg 2009;135 (2) 168- 172
PubMedArticle
8.
Lee  CHKim  JWLee  HJ  et al.  An investigation of upper airway changes associated with mandibular advancement device using sleep videofluoroscopy in patients with obstructive sleep apnea. Arch Otolaryngol Head Neck Surg 2009;135 (9) 910- 914
PubMedArticle
9.
Sforza  EKrieger  JBacon  WPetiau  CZamagni  MBoudewijns  A Determinants of effective continuous positive airway pressure in obstructive sleep apnea: role of respiratory effort. Am J Respir Crit Care Med 1995;151 (6) 1852- 1856
PubMedArticle
10.
Ng  ATQian  JCistulli  PA Oropharyngeal collapse predicts treatment response with oral appliance therapy in obstructive sleep apnea. Sleep 2006;29 (5) 666- 671
PubMed
11.
Sadaoka  TKakitsuba  NFujiwara  YKanai  RTakahashi  H The value of sleep nasendoscopy in the evaluation of patients with suspected sleep-related breathing disorders. Clin Otolaryngol Allied Sci 1996;21 (6) 485- 489
PubMedArticle
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