Obstructive Sleep Apnea Syndrome (OSAS) is a relatively common disorder in childhood that causes behavioral problems,1 attention and learning deficits, evidence of neuronal brain damage, increased cardiovascular risk profile, and poor quality of life.2–5 Habitual snoring rates vary significantly in the literature, depending on the definition adopted, the age group studied, and the questionnaire employed. The prevalence of chronic snoring found among Brazilian children was 27.6%, while 0.8% reported apnea, 15.5% described daytime mouth breathing, and 7.8% complained of excessive daytime sleepiness.6

The most common otorhinolaryngological disorder in children with OSAS is adenoid and tonsil hypertrophy, accompanied by allergic rhinitis, snore, mouth breathing, episodes of apnea, and restless sleep difficulties in swallowing saliva at night, as well as in chewing/swallowing, and postural changes.7

Adenotonsillectomy (AT) is the recommended first-line treatment for OSAS in children with adenotonsillar hypertrophy.8 However, a significant number of children with OSAS undergoing AT exhibit residual SDB after surgery.9 Although OSAS improved postoperatively, the proportion of patients who had residual OSAS ranged from 13% to 29% in low-risk populations to 73% when obese children were included, and stricter polysomnographic criteria were used.10 Possible factors influencing AT failure are patients with comorbidities, craniofacial anomalies, and nasal obstruction.11,12

Children with craniofacial anomalies with OSAS have a high-arched palate, increased mandibular plane angle, constricted upper and lower arches, and retrognathic mandible. Maxillary constriction deficiency plays a role in the etiology of severe respiratory disorders such as OSAS in growing individuals.12,13 Rapid Maxillary Expansion (RME) improves the nasal airway patency and effectively treats obstructive sleep apnea in children with maxillary constriction.14

Upper airway three-dimensional analysis and evaluation have received significant attention in the literature due to the more straightforward assessment and advantages provided by newer three-dimensional imaging techniques. Upper airway evaluation includes nasopharyngoscopy, cephalometry, multi-slice Computed Tomography (CT), Magnetic Resonance Imaging (MRI), and Cone-Beam Computed Tomography (CBCT) for visualization and measurement of the pharyngeal airway volume.15 There are differences in upper airway morphology and function between supine and upright positions during the acquisition of images generated by CT and CBCT for upper airway assessment.16 The airway of OSA patients was smaller when the patients were in a supine compared with an upright position. Airway changes in obstructive sleep apnea patients associated with a supine versus an upright position examined using cone-beam computed tomography.17

This prospective study aimed to investigate the effects of RME in children with residual snoring and obstructive sleep apnea after adenotonsillectomy, by correlating airway volumes using Multi-Slice Computed Tomography (MCT) and polysomnography.

Given the multifactorial nature of SDB, airway narrowing may be induced by obesity, adenotonsillar hypertrophy, retrognathia, or other factors that obstruct the airway.12,13,19 Patients with adequate weight may develop OSA due to craniofacial growth restriction, whereas obese patients typically present with soft tissue enlargement.

Craniofacial growth influenced by genetic inheritance and functional factors can impact on general health.21 Several studies prove that craniofacial morphology is a strong risk factor for pediatric SDB.22 Obstructive sleep apnea has been associated with deflections in craniofacial growth and development in children. A small maxilla or mandible can predispose the child to snore and obstructive sleep apnea.12,19,21 Orthodontic treatments such as RME,21,23 orthopedic orthodontic appliances,24 and functional orthodontic appliances25 can reduce snoring and OSA in ideal conditions during child growth and development.21 Effective treatment for SDB should target one or more risk factors to help cure the obstruction. Therefore, an accurate diagnosis of the etiology of SDB is crucial for treatment success, which must be multifaceted for all existing factors.19

Patients with maxillary transverse deficiency are predisposed to OSA and often present with tooth crowding and malocclusion, which can be treated by RME.26 RME is believed to decrease nasal resistance and facilitate the passage of air through the nose. In addition to improving the quality of nasal breathing, RME transversally increases the maxilla and thus enhances the tongue position, allowing proper lip sealing when the mouth is closed.23,27 It also indirectly increases the oropharyngeal space.

In a systematic review, Niu et al.28 studied the three-dimensional analyses of short- and long-term effects of rapid maxillary expansion on nasal cavity and upper airway. They concluded that there was an increase in the volume of the nasopharynx and oropharynx in the short term. However, more studies need to evidence these changes and the long-term stability of these results. Pirelli et al.29 confirmed the improvement of chronic snoring and OSA signs and symptoms with an increase in the total volume of the upper airways after RME in a recent study. We also confirmed these findings. In our research, the oropharynx volume in the total sample increased statistically significantly after RME compared to that observed before RME. As for the comparison between groups, the mean oropharyngeal volume was higher in the primary snoring group than in the OSA group; however, the differences were neither significant before nor after RME. Correlations values between saturation and oropharyngeal volume were not significant, both before RME and after RME. Based on the findings of the present investigation, it is not recommended to use volumetric changes of the airways after RME of children as a valid and reliable aspect to quantify breathing improvement. Most patients will show a degree of volumetric airway change that will not correlate to the quantitative breathing improvement.

Due to the complex nature of OSA, a multidisciplinary approach can optimize treatment. Although physicians are first-line providers in treatment and diagnosis, an integrated approach of health professionals including orthodontists, speech therapists, nutritionists, and psychologists can improve sleep-disordered breathing in childhood. Educating healthcare professionals about the potential benefits of RME is an essential step in interdisciplinary care. Assuming that craniofacial abnormalities are risk factors for SDB12 and can be corrected or minimized in a non-invasive manner only in childhood, new studies with larger samples are fundamental for preventing adult’s apnea.

Patients in this study will continue to be followed up to assess growth, development, and stability treatment benefits. In addition, complementary studies in association with other functional25 or fixed orthodontic appliances24 (for patients with skeletal class II) and myofunctional treatment30 to improve breathing and OSA should be considered to maintain or even improve the quality of life of these patients.

This study showed that when rapid maxillary expansion is performed in individuals with SDBs, there were statistically significant differences in oropharyngeal volume between pre-RME and post-RME. However, no correlation was found between oropharyngeal volume increase and oxygen saturation values.

This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) [grant number: 8882.430440/2019-01], and by Associação Fundo de Incentivo à Pesquisa (AFIP).

The authors declare no conflicts of interest.

No conflicts of interest of any kind were involved in the study. The funding sources had no involvement for the conduct of the research, preparation of the article, study design, collection, and analysis, interpretation of data, writing, and decision to submit the article for publication.