Abstract
To assess effectiveness of titratable Oral Appliance (OA) in management of moderate to severe cases of Obstructive Sleep Apnea (OSA). Thirty Polysomnography (PSG) diagnosed cases of moderate to severe OSA were subjected to a thorough cranio-facial-dental evaluation, a detailed sleep history and three dimensional assessment of upper airway geometry utilising Acoustic Pharyngometry (AP) (Eccovision, sleep group solutions). A titratable OA was delivered to all patients for mandibular advancement. Apnea Hypopnea Index (AHI), Oxygen Saturation (SPO2), Epworth's Sleepiness Scale (ESS), Mean area and volume of upper airway were recorded at Baseline (T0) and after 08 weeks of appliance delivery (T1). The mean AHI & ESS scores were significantly lower and SPO2 was significantly higher at T1 compared to T0 (P-value < 0.05 for all). The mean area and volume of upper airway at T1 were significantly higher compared to values at T0 (P-value < 0.05 for both). The mean area showed 19.51% increase at T1 whereas mean volume increased by 18.55%. OA therapy is highly efficacious in cases with moderate to severe OSA, especially, in those with retrognathic mandible. This modality should be considered as an effective alternate to Continuous Positive Airway Pressure (CPAP) therapy in non-compliant patients rather than no treatment. AP is an effective modality to predict airway changes after advancement with OA, to ascertain follow up changes and is highly recommended in routine clinical practice. Large scale, multicenter studies are recommended to elaborate the findings of the present study and to add better quality evidence in this regard.
Keywords: Oral appliance, Moderate, Severe, Obstructive sleep apnea, Acoustic pharyngometry
Introduction
Obstructive Sleep Apnea (OSA), a respiratory disorder, characterised by recurring episodes of cessation of breathing partially (hypopnea) or completely (apnea) due to partial or complete collapse of upper airway during sleep. It may lead to reduced ventilation, sleep fragmentation & interruption in normal sleep which manifests clinically as snoring, excessive daytime sleepiness, excessive fatigue, headaches and other related symptoms which reduce the overall quality of life [1, 2]. This emerging health problem, if left untreated, my lead to adverse health issues such as diabetes, hypertension and other cardiovascular, neural and cognitive disorders [3].
Continuous Positive Airway Pressure (CPAP) therapy; along with lifestyle modification in the form of dietary control, weight reduction, regular exercise, change in sleep posture etc., are the time-tested modalities for management of this condition. The CPAP keeps the airway open during sleep by forming a pneumatic splint in the upper airway, thereby preventing its collapse during sleep. But this therapy is associated with compliance issues due to uneasiness because of CPAP mask, portability issues, leakage from mask and dryness of mouth [4, 5]. Other modalities such as advancement of jaws by orthognathic surgery/ functional /oral appliances have been advocated in cases of non-compliance to CPAP therapy [6, 7].
The effectiveness of Oral Appliance (OA) therapy in the management of non-apneic snoring and mild to moderate OSA is well established [6–8]. However, there is limited evidence regarding their effectiveness in moderate to severe OSA cases, the majority of available literature being case reports/series and retrospective studies which are ranked lower in hierarchy of evidence. Further to this, most of the studies evaluating changes in upper airway have utilised either two dimensional (2D) radiographs like lateral cephalogram, three dimensional (3D) modalities like Cone Beam Computed Tomography (CBCT) or Magnetic Resonance Imaging (MRI). These modalities have disadvantage such as limited information with 2D radiographs and/ or additional radiation exposure & cost factors associated with 3D imaging [9, 10].
To overcome above limitations, the use of Acoustic Pharyngometry (AP) has been popularised recently to predict the expected benefit with mandibular advancement during treatment planning and to compare changes in upper airway during follow up. AP is based on acoustic reflection technique & incurs no radiation exposure to the patient. Literature reveals that its efficacy is comparable to above mentioned 2D and 3D modalities [10, 11].
Therefore, keeping the above perspectives into consideration, and to add quality evidence to the existing literature regarding the usefulness of OA therapy in moderate to severe OSA cases, this prospective study was undertaken.
Aim
This study aimed to assess the effectiveness of a titratable OA in management of moderate to severe cases of OSA utilising a non-invasive & non-ionising technique of AP.
Objectives
The objectives were:
To study changes in Apnea Hypopnea Index (AHI), Epworth's Sleepiness Scale (ESS) and (Oxygen Saturation) SPO2 after OA therapy in moderate to severe OSA cases.
To study changes in mean area and volume of upper airway after OA therapy in moderate to severe OSA cases.
Material and Methods
Study Design
Prospective clinical study.
Study Settings
The Polysomnography (PSG) diagnosed cases of OSA which were referred to the orthodontic clinic by the Sleep Medicine Department for opinion of the orthodontist regarding presence of craniofacial risk factors which may contribute to OSA were taken up for the present study. The patients were subjected to a thorough cranio-facial-dental evaluation, a detailed sleep related history and 3D assessment of upper airway geometry utilising AP equipment (Eccovision, sleep group solutions). The AP for all patients was recorded by a single calibrated operator as per standard recommendations of the manufacturers. A written informed consent was obtained from all patients for participation in the present study. The ethical approval was obtained from the institutional ethical committee.
Study Sample
The study sample consisted of patients diagnosed as cases with OSA (with type 1 PSG), treated at the orthodontic clinic between 01 Jan 2018 to 31 Dec 2020, both genders included, aged between 35 and 50 years with AHI between 15–45/per sleep hour (moderate to severe grade OSA), retrognathia of lower jaw evaluated cephalometrically with Point A-Nasion-Point B angle (ANB) > 4°, healthy dentition with sufficient teeth to support the OA, non-obese patients (BMI < 30 kg/m2) and neck circumference (NC) within normal range (i.e. < 42 cm). The subjects not included were those with sleep apnea due to central causes, recurrent episodes of nasal allergy, macroglossia, enlarged tonsils, any syndrome or disease affecting oro-pharyngeal airway, nasopharyngeal obstruction (deviated nasal septum or polyps), weak dentition not able to support the OA and cases which showed no improvement in airway on mandibular protrusion as shown by AP evaluation.
Variables
The variables studied were AHI, ESS, SPO2, mean area and mean volume of upper airway.
Outcome Variables
The change in the above variables was noted from pre-treatment (T0) to 08 weeks after delivery of OA (T1).
Methodology
Thirty-two patients who matched the selection criteria were taken up for OA therapy. Two patients were lost to follow up. Hence, the study was carried out on 30 patients. A detailed craniofacial examination and recording of sleep history, BMI and NC was done for all patients. The patients were asked to protrude their mandible to ascertain maximum protrusion, which was noted for all patients in their case sheets. The AP of all patients was recorded at rest position to ascertain mean area and volume of upper airway at baseline. A repeat AP was performed at 60% of maximum mandibular protrusion (which is the expected advancement by OA therapy) using Airway Metrics System, Mandibular Positioning Simulator System (Kettenbach, http://www.kettenbach-dental.us). Both the AP graphs obtained on the computer screen (Pharyngogram) were superimposed to quantify the expected change in upper airway area and volume after protrusion with OA (sample AP shown as Fig. 1). The AHI and SPO2 were recorded from the Type 1 (overnight & professionally monitored) PSG at a sleep centre at T0. ESS survey was done with the standard questionnaire survey distributed to the patients to quantify the subjective symptoms at baseline (T0). The baseline characteristics of the patients are shown as Table 1.
Fig. 1.
Acoustic Pharyngometry evaluation for improvement in airway at T1; Trial 1- baseline (T0); Trial 2- after mandibular protrusion (T1); % values showing % change in airway at T1
Table 1.
Baseline characteristics
| Parameters | Study sample (n = 30) | |
|---|---|---|
| Mean | SD | |
| Males (%) | 18 (60.0%) | – |
| Age (years) | 39.6 | 10.4 |
| BMI (kg/m2) | 26.91 | 1.54 |
| Neck circumference (cm) | 39.83 | 1.66 |
| AHI | 25.68 | 9.75 |
| SPO2 (%) | 90.97 | 1.88 |
| ESS | 18.20 | 2.90 |
As recommended by American Academy of Sleep Medicine (AASM) 2015 guidelines [6], a titratable OA, Medical Dental Sleep Appliance (MDSA Pty. Ltd. Registered design patents; Australian No.144305–2001; USA No.D450-6505–2001) (Fig. 2) was used for all patients. The bite recording was done using a George Gauge Bite (Scheu Group, Germany) at predetermined vertical height in the anterior and posterior region compatible with the MDSA screw. The appliance was fabricated at the departmental laboratory using vacuum formed thermoplastic sheets. The appliance was titrated at regular intervals during follow up with the help of titration key to optimise the subjective and objective benefits in the patients. All records i.e., PSG, AP and ESS were repeated at T1 to ascertain the effectiveness of the appliance. The entire study data was compiled in MS Excel sheets and was subjected to suitable statistical analyses.
Fig. 2.
Medical Dental Sleep Appliance
Statistical Analysis
The entire data was statistically analyzed using Statistical Package for Social Sciences (SPSS version 22.0, IBM Corporation, USA) for MS Windows. The pair-wise statistical comparison of the means of continuous variables was done using paired t test. The underlying normality assumption was tested before subjecting the study variables to statistical analysis. The p-values less than 0.05 were considered to be statistically significant. All the hypotheses were formulated using two tailed alternatives against each null hypothesis (hypothesis of no difference).
Results
Change in AHI, SPO2 ad ESS at T1
The mean AHI at T1 was significantly lower compared to mean AHI at T0 (P-value < 0.05). The mean SPO2 at T1 was significantly higher compared to mean SPO2 at T0 (P-value < 0.05). The mean ESS at T1 was significantly lower compared to mean ESS at T0 (P-value < 0.05) (Table 2, Fig. 3).
Table 2.
Change in AHI, SPO2 ad ESS at T1
| Parameters | T0 (n = 30) | T1 (n = 30) | P-value | ||
|---|---|---|---|---|---|
| Mean | SD | Mean | SD | ||
| AHI | 25.68 | 9.75 | 4.98 | 2.15 | 0.001*** |
| SPO2 (%) | 90.97 | 1.88 | 95.73 | 1.53 | 0.001*** |
| ESS | 18.20 | 2.90 | 4.77 | 1.61 | 0.001*** |
P-value < 0.05 indicates the statistically significant. NS-Statistically non-significant, *P-value < 0.05, **P-value < 0.01, ***P-value < 0.001
Fig. 3.
Change in Mean AHI, SPO2 and ESS at T1
Change in Mean Area and Volume at T1
The mean area and volume of upper airway at T1 was significantly higher compared to the values at T0 (P-value < 0.05). The mean area showed 19.51% increase at T1 whereas the mean volume increased by 18.55% (Table 3, Fig. 4).
Table 3.
Change in mean area and volume at T1
| Parameter | Time frame | Mean | SD | P-value (pre-versus post) |
|---|---|---|---|---|
| Mean Area (cm2) | Baseline (T0) | 2.25 | 0.34 | |
| 08 weeks after OA therapy (T1) | 2.69 | 0.35 | ||
| Change (T1-T0) | 0.43 | 0.10 | 0.039* | |
| % Change | 19.51 | – | 0.013* | |
| Mean Volume (cm3) | Baseline (T0) | 22.60 | 3.43 | |
| 08 weeks after OA therapy (T1) | 26.94 | 3.51 | ||
| Change (T1-T0) | 4.37 | 1.05 | 0.044* | |
| % Change | 18.55 | – | 0.011* |
P-value < 0.05 indicates the statistically significant. NS-Statistically non-significant, *P-value < 0.05, **P-value < 0.01, ***P-value < 0.001
Fig. 4.
Change in Mean area and Volume at T1
Discussion
The use of OA therapy in the management of OSA has increased in recent times, as an alternate to CPAP therapy [8, 12]. OA is considered as a second line of therapy, especially in cases of non-compliance to CPAP and in patients with favourable factors such as non-obese patients (i.e., BMI < 30 kg/m2) with lower grade of respiratory compromise, retruded lower jaw contributing to the airway compromise and in patients who can protrude their lower jaw to larger degrees (to obtain maximum increase in airway by OA) [13].
The majority of literature advocate OA therapy in mild to moderate grades of OSA taking into consideration various cardiovascular and neurologic comorbidities associated with severe OSA [14, 15]; some studies have reported efficacy of OA in severe OSA cases also [6, 13–16]. Therefore, to add further evidence regarding usefulness of OA in the management of moderate to severe OSA, a sample of 30 patients was selected, with favourable factors as listed above, to achieve best treatment outcome with OA. A titratable OA as advocated by AASM 2015 guidelines [6] was used at 60% initial advancement and titrated during follow up and monitored subjectively and objectively till best outcome was achieved. Only those patients with sufficient mandibular protrusion and who showed significant improvement in airway during pre-treatment simulation with airway metric system were included in the study.
Studies have shown that patients with OSA have reduced cross sectional areas of upper airway compared to normal subjects and AP has shown accuracy comparable with Computed Tomography (CT) and lateral cephalogram in measuring area and volume of upper airway at no radiation exposure to the patient [11, 17] and therefore, this modality was used to compare airway changes at follow up in the present study along with monitoring by PSG and ESS scores.
The parameters such as AHI, SPO2 & ESS, which mark the severity of OSA, showed significant improvement in the present study, showing efficacy of OA in management of cases with moderate to severe OSA, these findings are similar to other studies in literature which have documented improvement in OSA after OA therapy [18–20], but majority of these studies recommended their use in cases with mild to moderate OSA. Some studies, however, have reported success with OA therapy in reduction in severity of OSA in moderate to severe cases of OSA and have recommended their use, rather than no treatment, in patients who are non-complaint to CPAP and with associated risk factors [21, 22]. The mandibular protrusion & forward positioning of tongue brought about by the OA therapy expands the upper airway and prevents its collapse, thereby preventing the apneic & hypopneic episodes during sleep. Similar findings were observed in the present study, as seen by significant improvement in area and volume of upper airway in the present study, which were evaluated using AP. Similar improvement have been observed in other studies in literature which have utilised various 2D and 3D modalities [6, 8, 23–25]. However, majority of the studies have focussed on cases with mild to moderate OSA whereas, the present study focussed on cases with moderate to severe OSA.
Conclusions
The findings of the present study indicate that OA therapy is highly efficacious in cases with moderate to severe OSA, especially, in those with retrognathic mandible. This modality should be considered as an effective alternate to CPAP therapy in non-compliant patients rather than no treatment. AP is an effective modality to predict airway changes after advancement with OA, to ascertain follow up changes and is highly recommended in routine clinical practice. Large scale, multicenter studies are recommended to elaborate the findings of the present study and to add better quality evidence in this regard.
Funding
None.
Declarations
Conflict of interest
The authors declare that they have no competing interest.
Informed Consent
A written informed consent was obtained from all patients for participation in the present study.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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