Characterization of upper airway obstruction using cine MRI in children with residual obstructive sleep apnea after adenotonsillectomy

Surgical Management of Pediatric Obstructive Sleep Apnea Beyond Tonsillectomy & Adenoidectomy: Tongue Base and Larynx

Pediatric patients with persistent obstructive sleep apnea (OSA) after adenotonsillectomy often have additional sites of upper airway obstruction such as the tongue base or larynx. Sleep endoscopy and cross-sectional, dynamic imaging can be used to direct surgical management of persistent OSA. The tongue base is one of the most common sites of obstruction in children with persistent OSA, especially for patients with Trisomy 21. Lingual tonsillectomy, tongue suspension, and/or posterior midline glossectomy may be used to address lingual tonsil hypertrophy and tongue base obstruction. Epiglottopexy and/or supraglottoplasty may be used to address laryngomalacia and epiglottic prolapse resulting in OSA.

Alternatives to Polysomnography for the Diagnosis of Pediatric Obstructive Sleep Apnea

Diagnosis of obstructive sleep apnea (OSA) in children with sleep-disordered breathing (SDB) requires hospital-based, overnight level I polysomnography (PSG). Obtaining a level I PSG can be challenging for children and their caregivers due to the costs, barriers to access, and associated discomfort. Less burdensome methods that approximate pediatric PSG data are needed. The goal of this review is to evaluate and discuss alternatives for evaluating pediatric SDB. To date, wearable devices, single-channel recordings, and home-based PSG have not been validated as suitable replacements for PSG. However, they may play a role in risk stratification or as screening tools for pediatric OSA. Further studies are needed to determine if the combined use of these metrics could predict OSA.

Can Dynamic Magnetic Resonance Images Improve Prenatal Diagnosis of Robin Sequence

BACKGROUND

Robin sequence (RS) is a triad of micrognathia, glossoptosis, and airway obstruction. Prenatal diagnosis of RS improves delivery planning and postnatal care, but the process for prenatal diagnosis has not been refined. The purpose of this study was to determine if dynamic cine magnetic resonance imaging (MRI) can improve the reliability of prenatal diagnosis for RS compared to current static imaging techniques.

MATERIALS AND METHODS

This is a retrospective cross-sectional study including fetuses with prenatal MRIs obtained in a single center from January 2014 to November 2019. Fetuses were included if they: 1) had a prenatal MRI with cine dynamic sequences of adequate quality, 2) were live born, and 3) had postnatal craniofacial evaluation to confirm RS. Patients without postnatal confirmation of their prenatal findings were excluded. The primary predictor variable was imaging type (cine or static MRI). Outcome variables were tongue and airway measurements: 1) tongue height, 2) length and width, 3) tongue shape index, 4) observation of tongue touching the posterior pharyngeal wall, and 5) measurement of oropharyngeal space. All measurements were made independently on the cine images and on static MRI sequences for the same cohort of subjects by a pediatric radiologist. Data were analyzed using paired samples t tests and Fisher exact tests, and significance was set as P < .05.

RESULTS

A total of 11 patients with RS were included in the study. The smallest airway space consistently demonstrated complete collapse on the cine series compared to partial collapse on static images (0 mm vs 1.7 ± 1.4 mm, P = .002). No other imaging variable was statistically significantly different between techniques.

CONCLUSIONS

Cine imaging sequences on prenatal MRI were superior to static images in discerning complete collapse of the smallest airway space, an important marker of RS. This suggests a possible benefit to adding dynamic MRI evaluation for prenatal diagnosis of this condition.

Use of Polysomnography and CPAP in Children Who Received Adenotonsillectomy, US 2004 to 2018

OBJECTIVES

1) To determine the prevalence polysomnogram (PSG) and continuous positive airway pressure (CPAP) therapy use in children who received adenotonsillectomy (AT) for sleep symptoms. 2) To identify health care disparities in these regards.

STUDY DESIGN

Retrospective database analysis.

METHODS

This study used data from Optum (Health Services Innovation Company) to identify 92,490 children who received AT for sleep symptoms between 2004 and 2018. Prevalence of preoperative PSG and postoperative PSG and CPAP were described. Clinical and demographic characteristics were compared between children who had preoperative PSG and those who did not. Characteristics of children with trisomy 21 (T21) were compared to assess PSG and CPAP use in a high-risk cohort. Predictive modeling was used to identify patient characteristics associated with postoperative PSG and CPAP use.

RESULTS

Preoperative PSG was obtained in 5.5% of children overall and 33.2% of children with T21. Male sex, obesity, other medical comorbidities, non-White race/ethnicity, and higher parent education were associated with preoperative PSG. Fewer than 3% of children received postoperative PSGs and approximately 3% went on to receive CPAP therapy postoperatively. Multiple logistic regression showed that age at surgery, male sex, obesity, other medical comorbidities, non-White race/ethnicity, and higher parent education were associated with postoperative PSG and CPAP use.

CONCLUSIONS AND RELEVANCE

This study described the prevalence pre-AT PSG use and post-AT PSG and CPAP use for persistent symptoms and identified sleep health care disparities in these regards. These results show that increased, equitable access to PSG is needed in children, particularly in the workup and treatment persistent symptoms after AT.

LEVEL OF EVIDENCE

4 Laryngoscope, 133:184-188, 2023.

Changes in Cone-Beam Computed Tomography Pediatric Airway Measurements After Adenotonsillectomy in Patients With OSA

Importance

Early intervention using cone-beam computed tomography (CBCT) and adenotonsillectomy for children with obstructive sleep apnea (OSA) may prevent impaired growth, adverse cardiovascular consequences, learning deficits, and poor quality of life.

Objective

To assess changes in CBCT airway measurements and polysomnography (PSG) parameters that occur after adenotonsillectomy in children with OSA and to determine whether CBCT changes are correlated with apnea-hypopnea index (AHI) reduction.

Design, Setting, and Participants

This prospective cohort study was conducted at a tertiary medical center from 2013 to 2016. Children aged 7 to 13 years with PSG-confirmed OSA (ie, AHI ≥1) were recruited. Data analysis was performed from March to July 2021.

Exposures

All participants underwent CBCT and PSG before and after adenotonsillectomy.

Main Outcomes and Measures

Changes in PSG and CBCT parameters after adenotonsillectomy were analyzed.

Results

A total of 49 children (mean [SD] age, 9.5 [1.8] years; 34 boys [69.4%]) were recruited. Eighteen participants (36.7%) had obesity. After adenotonsillectomy, AHI significantly decreased from 11.4 to 1.2 events per hour (mean difference, -10.24 events per hour; 95% CI, -13.84 to -6.64 events per hour). The following CBCT parameters significantly increased: total airway volume (from 11 265 to 15 161 mm3; mean difference, 3896.6 mm3; 95% CI, 2788.0 to 5005.2 mm3), nasopharyngeal volume (from 2366 to 3826 mm3; mean difference, 1459.7 mm3; 95% CI, 1122.9 to 1796.5 mm3), minimal nasopharyngeal airway area (from 128 to 191 mm2; mean difference, 63.1 mm2; 95% CI, 47.4 to 78.8 mm2), mean nasopharyngeal airway area (from 144 to 231 mm2; mean difference, 86.8 mm2; 95% CI, 67.0 to 106.5 mm2), oropharyngeal volume (from 8898 to 11 335 mm3; mean difference, 2436.9 mm3; 95% CI, 1477.0 to 3396.8 mm3), minimal oropharyngeal airway area (from 82 to 158 mm2; mean difference, 76.2 mm2; 95% CI, 57.0 to 95.4 mm2), and mean oropharyngeal airway area (from 182 to 234 mm2; mean difference, 52.5 mm2; 95% CI, 33.6 to 71.4 mm2). Among all parameters, only body mass index percentile showed large effect size between the group with residual OSA (postoperative AHI ≥1) and the group with resolved disease, with the residual OSA group having a higher body mass index percentile (87.8 vs 61.4; mean difference, 26.33; 95% CI, 10.00 to 42.66). A quantile regression model revealed that total airway volume and minimal oropharyngeal airway area were significantly correlated with reductions in AHI.

Conclusions and Relevance

These findings suggest that in children undergoing adenotonsillectomy, improvements in total airway volume and oropharyngeal minimal airway area were correlated with reduction of AHI. Future studies are needed to assess whether CBCT has a role in the evaluation of children with OSA who are being considered for adenotonsillectomy.

Long-Term Non-invasive Ventilation in Children With Down Syndrome: A Systematic Review

Context

Children with Down syndrome are at risk for obstructive sleep apnea, which may not be resolved by adenotonsillecotmy, as well as other respiratory disorders that may impact breathing during sleep. Long-term non-invasive ventilation, including continuous and bilevel positive airway pressure delivery, is an alternate treatment strategy.

Objective

To assess the use and outcomes of long-term non-invasive ventilation in children with Down syndrome including comparison to other children using long-term non-invasive ventilation.

Data Sources

The search strategy for the scoping review used Medical Subject Headings (MeSH) and free-text terms for "child" and "non-invasive ventilation." MEDLINE (Ovid), Embase (Ovid), CINAHL (Ebsco), Cochrane Library (Wiley), and PubMed databases were searched (1990-2021).

Study Selection

The scoping review results were searched to identify studies including data on at least three children with Down Syndrome using long-term non-invasive ventilation.

Data Extraction

Study characteristics, subject characteristics, technology type, and outcome measurements were extracted.

Results

A total of 28 articles included 543 children with Down syndrome using long-term non-invasive ventilation. Children with Down syndrome accounted for 18% of children using long-term non-invasive ventilation. Data on efficacy, feasibility, and adherence in children with Down syndrome are comparable to other children. Children with Down syndrome may have greater difficulty initiating long-term non-invasive ventilation, longer time to establish use, and a higher rate of inability to establish use. Outcome data is limited but suggest favorable impact on cardiac function and attention.

Limitations

Articles related to long-term non-invasive ventilation use in adolescents and young adults may have been excluded.

Conclusions

Children with Down syndrome make up a significant portion of the population of children using long-term non-invasive ventilation. While there is more limited data available with respect to the use and outcomes for children with Down syndrome compared to the other children, long-term non-invasive ventilation is an effective and well-tolerated therapy with no clear differences in the use or outcomes for children with Down syndrome. Additional work is needed to understand potential challenges around establishing long-term non-invasive ventilation use in children with Down syndrome.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=206533, identifier: CRD206533.

Pediatric Obstructive Sleep Apnea: Update for the Primary Care Provider

Pediatric obstructive sleep apnea (OSA) is a common entity that can cause both daytime and nighttime issues. Children with symptoms should be screened for OSA. If possible, polysomnography should be performed to evaluate symptomatic children. Depending on the severity, first-line options for treatment of pediatric OSA may include observation, weight loss, medication, or surgery. Even after adenotonsillectomy, about 20% of children will have persistent OSA. Sleep endoscopy and cine MRI are tools that may be used to identify sites of obstruction, which in turn can help in the selection of site-specific treatment.

Persistent Obstructive Sleep Apnea in Children with Down Syndrome After Adenotonsillectomy: Drug Induced Sleep Endoscopy-Directed Treatment

ABSTRACT

Children with down syndrome (DS) are more liable to develop obstructive sleep apnea (OSA) which is usually treated with adenotonsillectomy. However, OSA may persist in many of those patients after the procedure. The aim of this study was to assess the efficacy of drug-induced sleep endoscopy (DISE)-directed treatment in management of DS children with persistent OSA after adenotonsillectomy. Sixteen DS children with persistent OSA after adenotonsillectomy were evaluated. DISE was done in the operating theatre to identify the site of obstruction, and surgical intervention was performed according to the finding. Polysomnographic study was used pre- and post-operatively to measure the outcome. DISE revealed obstruction in different sites of the airway. DISE-directed treatment was done according to the site of obstruction. Polysomnographic study showed postoperative significant changes for all parameters. The authors achieved improvement of overall apnea-hypopnea index which was normalized in seven patients (44%). In conclusion, DISE-directed treatment is an effective procedure for persistent OSA in DS children who underwent adenotonsillectomy. However, residual obstruction in those children may be due to many characteristic features that cause narrowing of the airway.

Neck fat and obstructive sleep apnea in obese adolescents

STUDY OBJECTIVES

Increased neck circumference, a surrogate for the neck fat that can narrow the upper airway in obese individuals, is a risk factor for obstructive sleep apnea syndrome (OSAS) in adults, but the association between neck fat and OSAS in adolescent males and females is unknown. We hypothesized that obese adolescents with OSAS have more neck fat than controls, females more neck fat than males, and that neck fat correlates with obesity and OSAS severity.

METHODS

Obese adolescents with OSAS and obese and normal-weight controls underwent upper airway magnetic resonance imaging, polysomnography, and anthropometrics, including neck circumference measurement. Intra-neck and subcutaneous neck fat measurements were manually segmented and compared among the three groups using ANOVA and between males and females using t-tests. The relationship between polysomnographic parameters and neck fat measurements was assessed in adolescents with OSAS using Pearson correlations.

RESULTS

One-hundred nineteen adolescents (38 females) were studied: 39 obese with OSAS, 34 obese controls, and 46 normal-weight controls. Neck fat was not greater in adolescents with OSAS compared to obese controls (p=0.35), and neck fat volume was not related to OSAS severity (p=0.36). However, obese adolescents had more neck fat than normal-weight controls (p<0.001), and neck fat volume correlated with neck circumference (r=0.53, p<0.001). Females had significantly greater cross-sectional neck fat than males (p<0.001).

CONCLUSIONS

While neck fat is associated with obesity and neck circumference in adolescents and is greater in females versus males, it does not appear to correlate with presence and severity of OSAS.

Comparison of Postoperative Analgesic Effects Between Nalbuphine and Fentanyl in Children Undergoing Adenotonsillectomy: A Prospective, Randomized, Double-Blind, Multicenter Study

Objective: There is no universal agreement on optimal pharmacological regimens for pain management during surgeries. The aim of this study to compare the postoperative analgesic effects of nalbuphine with fentanyl in children undergoing adenotonsillectomy.

Design, Setting, Participants: We conducted a prospective, randomized, double-blind, non-inferiority and multicenter trial in 311 patients admitted to four different medical facilities in China from October 2017 to November 2018.

Main Outcome Measure: The primary outcome was postoperative pain score. The secondary outcomes were as follows: the numbers of patients who developed moderate or severe pain (FLACC ≥4 points); time to first rescue analgesic top up and the actual number of rescue pain medicine given in pain control in post-anesthesia care unit (PACU), and additional analgesics requirement (received ≥2 rescue analgesics or/and other analgesics except study medications administered in PACU and ward); emergence and extubation time; Waking up time; time of PACU stay, and other side effects (desaturation, nausea/vomiting etc.).

Results: A total of 356 children were screened and 322 patients were randomized. The mean age was 5.8 (5.5, 6.1) in the nalbuphine group and 5.6 (5.3, 5.8) in the fentanyl group (p = 0.2132). FLACC score of nalbuphine group was lower than that of fentanyl group upon patients' arrival at PACU (p < 0.05). The time to first required rescue dose of pain drug for nalbuphine group was longer than for the fentanyl group (2.5 vs 1.2 h, p < 0.0001). Only one patient (0.6%) in nalbuphine group presented a slow respiratory rate (RR) at 9/min while 29 patients (18.5%) in fentanyl group developed slow RR ≤10/min in PACU. Meanwhile, SpO₂ was lower in the fentanyl group at 10 min after patients’ arrival in PACU (p < 0.05). The other profiles observed from these two drug groups were similar.

Conclusion: Nalbuphine provided better pain relief with minimal respiration depression than fentanyl in children undergoing Adenotonsillectomy.

Evaluation of Upper Airway in Children with Obstructive Sleep Apnea Using Cone-Beam Computed Tomography

OBJECTIVE

Cone-beam computed tomography (CBCT) offers three-dimensional structures in assessing upper airway of patients. This study aims to compare the cone-beam computerized tomography scan measurements between children with obstructive sleep apnea (OSA) and primary snoring.

STUDY DESIGN

Case-control study.

METHODS

This prospective study was conducted in a tertiary referral center. Thirty-six children with moderate-to-severe OSA (with apnea-hypopnea index [AHI] > 5 events/hour) and 36 age-, gender-, and obesity-matched children with primary snoring (AHI <1) were enrolled. The measurements in CBCT parameters were compared between children with moderate-to-severe OSA and primary snorers by conditional logistic regression model.

RESULTS

A total of 72 children (mean age, 7.9 ± 2.8 years; 64% male) were included. Children with moderate-to-severe OSA had a significantly smaller nasopharyngeal (2900 ± 1400 vs. 3800 ± 1800 mm³ , P = .017) and oropharyngeal airway volume (5600 ± 2700 vs. 7400 ± 4000 mm³ , P = .026) than those with primary snoring. Children with moderate-to-severe OSA, as compared to primary snorers, also had a significantly smaller minimal airway area in nasopharynx (77.4 ± 37.7 vs. 107.7 ± 52.0 mm² , P = .006) and oropharynx (66.6 ± 61.9 vs. 101.6 ± 65.8 mm² , P = .023). Moreover, the airway length was not significantly different between children with moderate-to-severe OSA and primary snoring.

CONCLUSIONS

The three-dimensional CBCT airway analysis could be used as a useful tool to evaluate upper airway in children with OSA.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:680-685, 2021.

Alternative Approaches to Adenotonsillectomy and Continuous Positive Airway Pressure (CPAP) for the Management of Pediatric Obstructive Sleep Apnea (OSA): A Review

Continuous positive airway pressure (CPAP) is considered first-line treatment in the management of pediatric patients without a surgically correctible cause of obstruction who have confirmed moderate-to-severe obstructive sleep apnea (OSA). The evidence supports its reduction on patient morbidity and positive influence on neurobehavioral outcome. Unfortunately, in clinical practice, many patients either refuse CPAP or cannot tolerate it. An update on alternative approaches to CPAP for the management of OSA is discussed in this review, supported by the findings of systematic reviews and recent clinical studies. Alternative approaches to CPAP and adenotonsillectomy for the management of OSA include weight management, positional therapy, pharmacotherapy, high-flow nasal cannula, and the use of orthodontic procedures, such as rapid maxillary expansion and mandibular advancement devices. Surgical procedures for the management of OSA include tongue-base reduction surgery, uvulopalatopharyngoplasty, lingual tonsillectomy, supraglottoplasty, tracheostomy, and hypoglossal nerve stimulation. It is expected that this review will provide an update on the evidence available regarding alternative treatment approaches to CPAP for clinicians who manage patients with pediatric OSA in daily clinical practice.

Treatment of Obstructive Sleep Apnea in Children: Handling the Unknown with Precision

Treatment approaches to pediatric obstructive sleep apnea (OSA) have remarkably evolved over the last two decades. From an a priori assumption that surgical removal of enlarged upper airway lymphadenoid tissues (T&A) was curative in the vast majority of patients as the recommended first-line treatment for pediatric OSA, residual respiratory abnormalities are frequent. Children likely to manifest persistent OSA after T&A include those with severe OSA, obese or older children, those with concurrent asthma or allergic rhinitis, children with predisposing oropharyngeal or maxillomandibular factors, and patients with underlying medical conditions. Furthermore, selection anti-inflammatory therapy or orthodontic interventions may be preferable in milder cases. The treatment options for residual OSA after T&A encompass a large spectrum of approaches, which may be complementary, and clearly require multidisciplinary cooperation. Among these, continuous positive airway pressure (CPAP), combined anti-inflammatory agents, rapid maxillary expansion, and myofunctional therapy are all part of the armamentarium, albeit with currently low-grade evidence supporting their efficacy. In this context, there is urgent need for prospective evidence that will readily identify the correct candidate for a specific intervention, and thus enable some degree of scientifically based precision in the current one approach fits all model of pediatric OSA medical care.

Preoperative identification of children at high risk of obstructive sleep apnea

Obstructive sleep apnea is a common childhood disorder which can lead to serious health problems if left untreated. Enlarged adenoid and tonsils are the commonest causes, and adenotonsillectomy is the recommended first line of treatment. Obstructive sleep apnea poses as an anesthetic challenge, and it is a well-known risk factor for perioperative adverse events. The presence and severity of an obstructive sleep apnea diagnosis will influence anesthesia, pain management, and level of monitoring in recovery period. Preoperative obstructive sleep apnea assessment is necessary, and anesthetists are ideally placed to do so. Currently, there is no standardized approach to the best method of preoperative screening for obstructive sleep apnea. Focused history, clinical assessments, and knowledge regarding the strengths and limitations of available obstructive sleep apnea assessment tools will help recognize a child with obstructive sleep apnea in the preoperative setting.

Updates on management of pediatric obstructive sleep apnea

Obstructive sleep apnea (OSA) affects about 1%-5% of the pediatric population. The consequences of untreated OSA in children include neurocognitive deficits, behavioral problems, poor school performance as well as systemic and pulmonary hypertension. The treatment options for pediatric OSA are numerous with a variety of surgical and non-surgical interventions. As our understanding of the complexities of OSA grows, the options for management have continued to expand as well. The objectives of this review are to describe the commonly prescribed treatments for pediatric OSA including adenotonsillectomy as well as use of positive airway pressure. We also highlight other surgical and non-surgical interventions available. In addition, we provide updates on current research focusing on newer diagnostic and experimental treatment modalities.

Associations among sleep symptoms, physical examination, and polysomnographic findings in children with obstructive sleep apnea

PURPOSE

The relationships among PSG findings, OSA symptoms, and tonsil and adenoid size are not clear. In this study, we aimed to investigate the associations between pediatric OSA and tonsil and adenoid size using subjective (OSA-18 questionnaire) and objective (PSG) measurements.

METHODS

101 consecutive patients aged from 2 to 12 years (mean age, 5.4 ± 2.2 years; boys, 72.3%) diagnosed with OSA were enrolled in two age groups (2-6 years group and 7-12 years group) and underwent PSG and lateral cephalometric radiography. Tonsil size and the adenoid-nasopharyngeal (A/N) ratio were determined. Quality of life and sleep symptoms were measured using the Chinese version OSA-18 questionnaire. Demographic and clinical data were obtained.

RESULTS

75 and 26 patients were separately enrolled in 2-6 years group and 7-12 years group. In 2-6 years group, the multiple linear regression revealed that tonsil size and A/N ratio were associated with log apnea-hypopnea index (AHI), and the Spearman's rank correlation reflected a positive correlation between log AHI and the OSA-18 sleep disturbance score (r = 0.362, P = 0.001). Log OSA-18 score was correlated with tonsil size (r = 0.349, P = 0.002) but not the A/N ratio in 2-6 years group. Finally, no significant associations were observed between log OSA-18 scores and log AHI in all patients.

CONCLUSION

As PSG stays the golden standard for diagnoses of pediatric OSA, physical examinations and quality-of-life assessments are needed to fully assess the impact of OSA on children.

Upper airway visualization in pediatric obstructive sleep apnea

Pediatric Obstructive Sleep Apnea (OSA) is a condition that may lead to a variety of comorbidities in adolescence and adulthood. The gold standard of diagnosing OSA is polysomnography (PSG). Over the past fifteen years numerous publications have explored how to better visualize the upper airway to further assess OSA in the pediatric population, and eventually institute personalized treatment. Lateral neck radiograph, cephalometry, computed axial tomography, and magnetic resonance imaging are all unique imaging techniques that are used in the diagnosis of OSA. Drug Induced Sleep Endoscopy is a direct visualization technique that is gathering momentum in pediatrics. Each approach has respective benefits and weaknesses. However, none of them at this time can replace PSG. They are a helpful supplement in those patients with complicated upper airway anatomy and in those with residual OSA.

Changes in the upper airway following induction of anaesthesia: a prospective observational study protocol to determine the use of ultrasound in the assessment of a difficult airway in China

INTRODUCTION

Difficult airway management is closely related to the safety and quality of medical care. However, the low incidence of correct prediction of difficult airway in clinical screening tests presents physicians with a dilemma. Depressed airway neuromuscular tension during sleep and anaesthesia tends to cause collapse of fragile parts of the upper airway. Although previous studies have confirmed that anterior cervical tissue thickness is associated with difficult airways, there is no evidence to support a correlation between a difficult airway and specific patterns or findings of anaesthesia-induced airway collapse. Thus, this study aims to examine changes in airway dimensions before and after induction of general anaesthesia to explore whether it could provide useful information regarding the specific anatomic changes occurring which may cause difficult airways.

METHODS AND ANALYSIS

This will be a single-centre prospective observational single-blinded study, conducted in a tertiary teaching hospital in Guangzhou, China. Subjects will be recruited from patients (aged 18-65 years) scheduled for elective surgery under general anaesthesia. Sonographic measurement will be performed to detect changes in the thickness of the anterior cervical soft tissue before and after anaesthetic induction. Based on the resulting data distribution, analyses will initially compare these changes using a paired t-test or the Wilcoxon signed-rank test. The correlation of sonographic changes and Cormack-Lehane grade will be evaluated by using receiver-operating characteristic curves to detect the sensitivity and specificity of a measurement for detecting difficulties. Linear stepwise regression analysis will be used to assess the correlation between airway changes and demographic variables as well as clinical tests.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the Ethics Committee of the First Affiliated Hospital of Guangzhou University of Chinese Medicine (ZYYECK (2018) 041). The results will be disseminated through conference presentations, professional journals and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

ChiCTR1900021123; Pre-results.