Sleep Breath DOI 10.1007/s11325-014-0947-3

ORIGINAL ARTICLE

Videoendoscopic diagnosis for predicting the response to oral appliance therapy in severe obstructive sleep apnea Yasuhiro Sasao & Kanji Nohara & Kentaro Okuno & Yuki Nakamura & Takayoshi Sakai

Received: 21 July 2013 / Revised: 19 January 2014 / Accepted: 28 January 2014 # Springer-Verlag Berlin Heidelberg 2014

Abstract Purpose In treatment for obstructive sleep apnea (OSA), oral appliance (OA) therapy is indicated in patients with mild– moderate OSA. However, since patients with severe OSA in whom OA therapy was effective have also been reported, it may not be possible to determine indications for OA therapy based on the severity alone. The purpose of this study was to determine indications for OA therapy using endoscopy during wakefulness in patients with severe OSA. Methods The subjects consisted of 36 patients (27 males and 9 females) diagnosed with severe OSA using all-night polysomnography. In each patient, a nasoendoscope was inserted in a horizontal position during nasal breathing, and morphological changes in the airway of the velopharynx and oro-hypopharynx with mandibular advancement were evaluated. Results With mandibular advancement, the oro-hypopharynx was widened in all patients while the velopharynx was widened in 29 patients, but not in 7. The apnea hypopnea index (AHI) reduction rate after OA application was 79.8 % (SD, 13.0 %) in the group with and 40.6 % (SD, 27.0 %) in the group without velopharyngeal widening, being significantly different between the two groups. In the group showing velopharyngeal widening, evaluation of the direction of Y. Sasao (*) Sasao Dental Clinic, Center for Oral Functional Disorders, 1-23-18, Nakatsumachi, Iwakuni City, Yamaguchi 740-0027, Japan e-mail: [email protected] K. Nohara (*) : K. Okuno : Y. Nakamura : T. Sakai Division for Oral-Facial Disorders, Osaka University Dental Hospital, 1-8, Yamadaoka, Suita City, Osaka 565-0871, Japan e-mail: [email protected] T. Sakai Division for Oral-Facial Disorders, Osaka University Graduate School of Dentistry, Osaka, Japan

widening revealed two types: the “all-round type”, which is circumferential widening in the anteroposterior–lateral directions, and the “lateral dominant type”, which is widening mainly in the lateral direction. The AHI reduction rate was 80.1 % (SD, 15.0 %) for the all-round type and 79.3 % (SD, 10.6 %) for the lateral dominant type showing no significant difference. Discussion (1) Concerning indications for OA therapy, findings in the velopharynx rather than those in the hypopharynx may be important. (2) The effects of OA therapy can be expected in the presence of velopharyngeal widening irrespective of its direction. Thus, to determine whether OA therapy is indicated, endoscopic evaluation of morphological changes in the velopharynx with mandibular advancement may be important. Keyword Endoscopy . Sleep apnea . Oral appliance . Velopharynx . Predict

Introduction One of the treatment methods for obstructive sleep apnea (OSA) is oral appliance (OA) therapy, which widens the airway or decreases airway resistance by mandibular advancement to maintain a patent respiratory tract. This therapy has been reported to be effective in 50–80 % of patients [1–5], and there are patients who readily respond and those with difficultly responding to this therapy. The Guidelines of the American Academy of Sleep Medicine (AASM) state that OA therapy is indicated in patients with mild–moderate OSA or those in whom CPAP is not indicated [6]. Thus, based on the severity using the apnea hypopnea index (AHI) as a parameter, patients in whom OA therapy is indicated are selected at present. However, patients with severe OSA who responded to

Sleep Breath

OA therapy have also been reported [7]. Therefore, whether OA therapy is indicated cannot be determined based on the severity alone. To determine whether it is indicated, not only the use of AHI but also the prediction of treatment effects by appropriate pretreatment evaluation is necessary. For determination, evaluation of morphological changes in the upper airway as the obstructive area with mandibular advancement is of primary importance. For this, cephalometry, computerized tomography (CT), magnetic resonance imaging (MRI), and transnasal endoscopy are used [8, 9]. Among these methods, transnasal endoscopy allows observation of the horizontal plane of the pharynx and evaluation of the time course of dynamic morphological changes in the pharynx in the anteroposterior and lateral directions with expiration–inspiration. Therefore, this method, as with sleep fiber optic endoscopy, is used as an examination for the upper airway [7]. Sleep fiber optic endoscopy is performed in combination with all-night polysomnography (PSG), but rarely used in clinical practice due to the complexity of the procedure and time and labor involved in the medical care system. In this study, we used nasoendoscopy during wakefulness to increase its clinical usefulness, and evaluated the association between morphological changes in the airway with mandibular advancement and the effects of OA therapy during sleep in order to determine indications for OA therapy.

OA For each patient, an OA to fix the mandible in the advanced position was produced. Using maxillary and mandibular plaster casts, acrylic plates (ERKODENT®) were molded employing a hot compression molding apparatus into maxillary and mandibular mouthpieces. These mouthpieces were fixed in each subject’s oral cavity using quick-cure resin. The mandible was fixed in a position as forward as possible without causing side effects such as pain of the teeth or temporomandibular joint. In all subjects, the mandibular position was 2/3 or more of the maximum protrusion. Endoscopy and test task Endoscopy was performed using a flexible nasoendoscope (FNL-10RP3, PENTAX) by dentists with ≥7 years of clinical endoscopy experience. In each patient, the nasoendoscope was inserted in a supine position during nasal breathing while lying on a bed, and two areas (the velopharynx and orohypopharynx) were observed. As a test task, each subject was asked to move the mandible from the centric occlusal to maximum forward position five times without OA. Endoscopic images obtained while performing the task were captured using a DVD recorder. Evaluation methods

Methods Subjects The subjects consisted of all 36 Japanese patients (27 males and 9 females) who visited Osaka University Dental Hospital during the 7 years between 2005 and 2012, and were diagnosed with severe OSA syndrome (AHI≥30) using all-night PSG. Their mean age was 57.6 (±11.6)years, and the mean body mass index (BMI) was 24.5 (±3.3). This study was performed with the approval of the Ethical Committee of Osaka University Dental Hospital (H19-E3-1) and consent of all subjects.

In the velopharynx and oro-hypopharynx, changes in the airway due to the test task were classified as “no widening” or “widening” (Table 1), and the direction of widening was classified as “anteroposterior” and/or “lateral”. Evaluation was performed by consultation between two dentists with 7 years of clinical endoscopy experience. In each patient, an OA was produced, PSG was performed with use of the OA, and the AHI before as well as after OA application was obtained. Based on the AHI, the AHI reduction rate after OA application was calculated, and compared between groups with or without widening in the velopharynx or oro-hypopharynx. In addition, in the group showing widening, to evaluate the influences of the direction of widening on the AHI reduction rate, this rate was compared between the groups primarily showing anteroposterior or lateral widening.

All-night PSG Statistical analysis Apnea in all-night PSG was defined as the cessation of airflow at ≥10 s. Hypopnea was defined as a respiratory event causing a ≥50 % reduction in airflow with a ≥3 % peripheral artery oxygen desaturation (SpO2) persisting for ≥10 s or requiring arousal. The AHI was defined as the total number of apnea and hypopnea events per hour [10].

Data were expressed as mean and standard deviation (SD). All data were analyzed by Microsoft Excel Statistics software. Welch’s t test was used for comparison of parameters between two groups. P values < 0.01 was considered statistically significant.

Sleep Breath Table 1 Example of endoscopic evaluation of the morphological changes in the oro-hypopharynx and velopharynx with mandibular advancement

Oro-hypopharynx

Centric occlusal position

Advancing the mandible

Widened

Not widened

No subject

All-round type

Widened Lateral dominant type

Not widened

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Results In all patients, the AHI decreased after OA application. As shown in Table 2, when the patients were arranged in decreasing order of the AHI reduction rate, oro-hypopharyngeal widening was observed in all patients while velopharyngeal widening was observed in some patients but not in others, and the ranks of patients showing no widening tended to be low. In the velopharynx, the AHI reduction rate was 79.8 % (SD,

13.0 %) in the group with and 40.6 % (SD, 27.0 %) in the group without widening, being significantly different between the two (t=3.742, P=0.004; Fig. 1). In the group showing velopharyngeal widening, evaluation of the direction of widening revealed two types: the “all-round type”, which is circumferential widening in the anteroposterior–lateral directions and the “lateral dominant type”, which is widening mainly in the lateral direction (Table 2). The AHI reduction rate was 80.1 % (SD, 15.0 %)

Table 2 Nasoendoscopic findings of the pharynx with mandibular advancement Gender

Age

BMI

AHI Pre-OA

AHI reduction rate

Oro-hypopharynx

Velopharynx

Type of velopharyngeal widening

With OA

M M M

60 35 72

16.9 23.5 24.6

64.3 34.3 33.1

2.1 1.3 1.4

96.7 96.2 95.8

Widened Widened Widened

Widened Widened Widened

All-round All-round All-round

M M F F F M M F M M M F F F M M M M

60 68 51 60 54 69 37 57 40 69 59 65 48 64 56 62 58 59

22.9 19.1 24.7 24.9 29.4 23.9 26.0 22.2 18.9 26.6 21.6 21.6 26.1 17.8 24.0 23.4 25.6 21.7

32.0 33.8 30.2 45.2 50.0 38.5 51.6 46.1 39.6 60.0 36.8 39.0 37.1 37.5 34.0 34.1 54.5 40.8

1.7 2.4 2.4 3.7 4.5 3.7 5.3 6.1 5.4 8.5 5.3 6.2 6.0 7.0 8.4 8.8 14.2 11.0

94.7 92.9 92.1 91.8 91.0 90.4 89.7 86.8 86.4 85.8 85.6 84.1 83.8 81.3 75.3 74.2 73.9 73.0

Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened

Widened Widened Widened Widened Widened Widened Not widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened

Lateral dominant Lateral dominant All-round Lateral dominant All-round All-round – All-round Lateral dominant Lateral dominant All-round Lateral dominant All-round All-round Lateral dominant Lateral dominant All-round Lateral dominant

M M M F F M M M M M M M M M M

71 50 78 60 73 69 54 54 36 72 41 53 47 40 71

23.7 26.2 23.5 30.0 27.6 26.2 28.8 25.7 24.6 27.0 25.4 24.6 24.8 31.6 28.1

48.8 50.4 55.8 41.9 36.1 34.7 30.6 51.1 56.6 35.6 44.9 38.6 64.1 32.6 37.3

13.8 14.3 15.9 12.7 11.3 13.5 12.1 20.3 25.7 19.1 24.5 24.7 43.9 25.4 35.5

71.7 71.6 71.5 69.7 68.7 61.1 60.5 60.3 54.6 46.3 45.4 36.0 31.5 22.1 4.8

Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened Widened

Widened Widened Widened Widened Widened Widened Widened Widened Not widened Widened Not widened Not widened Not widened Not widened Not widened

All-round Lateral dominant Lateral dominant Lateral dominant All-round All-round All-round Lateral dominant – All-round – – – – –

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90

AHI reduction rate (%)

80 70 60 50 40 30 20 10 P