Functional respiratory imaging as a tool to assess upper airway patency in children with obstructive sleep apnea

Diagnosis of Paediatric Obstructive Sleep-Disordered Breathing beyond Polysomnography

Obstructive sleep-disordered breathing (SDB) has significant impacts on health, and therefore, a timely and accurate diagnosis is crucial for effective management and intervention. This narrative review provides an overview of the current approaches utilised in the diagnosis of SDB in children. Diagnostic methods for SDB in children involve a combination of clinical assessment, medical history evaluation, questionnaires, and objective measurements. Polysomnography (PSG) is the diagnostic gold standard. It records activity of brain and tibial and submental muscles, heart rhythm, eye movements, oximetry, oronasal airflow, abdominal and chest movements, body position. Despite its accuracy, it is a time-consuming and expensive tool. Respiratory polygraphy instead monitors cardiorespiratory function without simultaneously assessing sleep and wakefulness; it is more affordable than PSG, but few paediatric studies compare these techniques and there is optional recommendation in children. Nocturnal oximetry is a simple and accessible exam that has high predictive value only for children at high risk. The daytime nap PSG, despite the advantage of shorter duration and lower costs, is not accurate for predicting SDB. Few paediatric data support the use of home testing during sleep. Finally, laboratory biomarkers and radiological findings are potentially useful hallmarks of SDB, but further investigations are needed to standardise their use in clinical practice.

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.

Does rapid maxillary expansion improve nasal airway obstruction? A computer fluid dynamics study in patients with nasal mucosa hypertrophy and obstructive adenoids

INTRODUCTION

Rapid maxillary expansion (RME) expands the maxillary dentition laterally and improves nasal airway obstruction. However, the incidence of nasal airway obstruction improvement after RME is approximately 60%. This study aimed to clarify the beneficial effects of RME on nasal airway obstruction in specific pathologic nasal airway diseases (nasal mucosa hypertrophy and obstructive adenoids) using computer fluid dynamics.

METHODS

Sixty subjects (21 boys; mean age 9.1 years) were divided into 3 groups according to their nasal airway condition (control, nasal mucosa hypertrophy, and obstructive adenoids), and those requiring RME had cone-beam computed tomography images taken before and after RME. These data were used to evaluate the nasal airway ventilation condition (pressure) using computer fluid dynamics and measure the cross-sectional area of the nasal airway.

RESULTS

The cross-sectional area of the nasal airway significantly increased after RME in all 3 groups. The pressures in the control and nasal mucosa groups significantly reduced after RME but did not change significantly in the adenoid group. The incidence of improvement in nasal airway obstruction in the control, nasal mucosa, and adenoid groups was 90.0%, 31.6%, and 23.1%, respectively.

CONCLUSIONS

The incidence of improvement in nasal airway obstruction after RME depends on the nasal airway condition (nasal mucosa hypertrophy and obstructive adenoids). In patients with nonpathologic nasal airway conditions, the obstruction may be sufficiently improved with RME. Furthermore, to some extent, RME may be effective in treating nasal mucosa hypertrophy. However, because of obstructive adenoids, RME was ineffective in patients with nasal airway obstruction.

Diagnostic value of upper airway morphological data based on CT volume scanning combined with clinical indexes in children with obstructive sleep apnea syndrome

Background and purpose

Early diagnosis is important for treatment and prognosis of obstructive sleep apnea (OSA)in children. Polysomnography (PSG) is the gold standard for the diagnosis of OSA. However, due to various reasons, such as inconvenient implementation, less equipped in primary medical institutions, etc., it is less used in children, especially in young children. This study aims to establish a new diagnostic method with imaging data of upper airway and clinical signs and symptoms.

Methods

In this retrospective study, clinical and imaging data were collected from children ≤10 years old who underwent nasopharynx CT scan(low-dose protocol)from February 2019 to June 2020,including 25 children with OSA and 105 non-OSA. The information of the upper airway (A-line; N-line; nasal gap; upper airway volume; upper and lower diameter, left and right diameter and cross-sectional area of the narrowest part of the upper airway) were measured in transaxial, coronal, and sagittal images. The diagnosis of OSA and adenoid size were given according to the guidelines and consensus of imaging experts. The information of clinical signs, symptoms, and others were obtained from medical records. According to the weight of each index on OSA, the indexes with statistical significance were screened out, then were scored and summed up. ROC analysis was performed with the sum as the test variable and OSA as the status variable to evaluate the diagnostic efficacy on OSA.

Results

The AUC of the summed scores (ANMAH score) of upper airway morphology and clinical index for the diagnosis of OSA was 0.984 (95% CI 0.964–1.000). When sum = 7 was used as the threshold (participants with sum>7 were considered to have OSA), the Youden’s index reached its maximum at which point the sensitivity was 88.0%, the specificity was 98.1%, and the accuracy was 96.2%.

Conclusion

The morphological data of the upper airway based on CT volume scan images combined with clinical indices have high diagnostic value for OSA in children; CT volume scanning plays a great guiding role in the selection of treatment scheme of OSA. It is a convenient, accurate and informative diagnostic method with a great help to improving prognosis.

Upper Airway Flow Dynamics in Obstructive Sleep Apnea Patients with Various Apnea-Hypopnea Index

BACKGROUND AND AIM

This study evaluates the upper airway flow characteristics, anatomical features and analyzes their correlations with AHI in patients with varied degrees of OSA severity seeking for discernments of the underlying pathophysiological profile.

MATERIALS AND METHODS

Patient-specific computational fluid dynamics models were reconstructed from high-resolution cone-beam computed tomography images for 4 OSA patients classified as minimal, mild, moderate, and severe according to AHI.

RESULTS

The parameters, minimal cross-sectional area (MCA), and the pharyngeal airway volume did not show clear correlations with the OSA severity defined according to AHI. No correlations were found between the classically defined resistance of the airway in terms of pressure drop and AHI. The flow analysis further showed that the fluid mechanisms likely to cause airway collapse are associated with the degree of narrowing in the pharyngeal airway rather than AHI. Results also suggested that some patients classified as severe OSA according to the AHI can show less susceptibility to airway collapse than patients with relatively lower AHI values and vice versa.

CONCLUSIONS

The relative contribution of anatomical and non-anatomical causes to the OSA severity can significantly vary between patients. AHI alone is inadequate to be used as a marker of the pathophysiological profile of OSA. Combining airflow analysis with AHI in diagnosing OSA severity may provide additional details about the underlying pathophysiology, subsequently improving the individualized clinical outcomes.

Effect of adenoids and tonsil tissue on pediatric obstructive sleep apnea severity determined by computational fluid dynamics

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is a respiratory disorder caused by the obstruction of the upper airway during sleep. The most common cause of pediatric OSA is adenotonsillar hypertrophy. Adenotonsillectomy is the first-line treatment for pediatric OSA; however, OSA persists in a significant number of patients due, in part, to the method of evaluating enlarged adenoids and tonsil tissue. The reason for these effects on OSA severity is not clear. This study aimed to establish a method to diagnose the need for adenoidectomy or tonsillectomy.

METHODS

Twenty-seven Japanese children (mean age 6.6 years) participated in this study, undergoing polysomnography and computed tomography examination. Pharyngeal airway morphology (adenoids and tonsil tissue size, volume, and cross-sectional area [CSA]) and pressure on the upper airway were evaluated at each site using computational fluid dynamic analysis.

RESULTS

Apnea-hypopnea index (AHI) showed a strong linear association with maximum negative pressure (P_max) (AHI = -0.055* events/h P_max -1.326, R² = .805). The relationship between minimum CSA (CSA_min) and P_max was represented by an inversely proportional fitted curve (P_max = -4797/CSA_min -5.1, R² = .507). The relationship between CSA_min and AHI was also represented by an inversely proportional fitted curve (AHI = 301.6 events/h/CSA_min ^1.22, R² = .680). P_max greatly increased if CSA_min became ≤ 30 mm². The negative pressure of each site increased when CSA measured ≤ 50 mm².

CONCLUSIONS

In children, when the CSA for each site is ≤ 50 mm², AHI is likely to be elevated, and the patient may require tonsillectomy or adenoidectomy.

Computational fluid dynamics modelling of human upper airway: A review

BACKGROUND AND OBJECTIVE

Human upper airway (HUA) has been widely investigated by many researchers covering various aspects, such as the effects of geometrical parameters on the pressure, velocity and airflow characteristics. Clinically significant obstruction can develop anywhere throughout the upper airway, leading to asphyxia and death; this is where recognition and treatment are essential and lifesaving. The availability of advanced computer, either hardware or software, and rapid development in numerical method have encouraged researchers to simulate the airflow characteristics and properties of HUA by using various patient conditions at different ranges of geometry and operating conditions. Computational fluid dynamics (CFD) has emerged as an efficient alternative tool to understand the airflow of HUA and in preparing patients to undergo surgery. The main objective of this article is to review the literature that deals with the CFD approach and modeling in analyzing HUA.

METHODS

This review article discusses the experimental and computational methods in the study of HUA. The discussion includes computational fluid dynamics approach and steps involved in the modeling used to investigate the flow characteristics of HUA. From inception to May 2020, databases of PubMed, Embase, Scopus, the Cochrane Library, BioMed Central, and Web of Science have been utilized to conduct a thorough investigation of the literature. There had been no language restrictions in publication and study design of the database searches. A total of 117 articles relevant to the topic under investigation were thoroughly and critically reviewed to give a clear information about the subject. The article summarizes the review in the form of method of studying the HUA, CFD approach in HUA, and the application of CFD for predicting HUA obstacle, including the type of CFD commercial software are used in this research area.

RESULTS

This review found that the human upper airway was well studied through the application of computational fluid dynamics, which had considerably enhanced the understanding of flow in HUA. In addition, it assisted in making strategic and reasonable decision regarding the adoption of treatment methods in clinical settings. The literature suggests that most studies were related to HUA simulation that considerably focused on the aspects of fluid dynamics. However, there is a literature gap in obtaining information on the effects of fluid-structure interaction (FSI). The application of FSI in HUA is still limited in the literature; as such, this could be a potential area for future researchers. Furthermore, majority of researchers present the findings of their work through the mechanism of airflow, such as that of velocity, pressure, and shear stress. This includes the use of Navier-Stokes equation via CFD to help visualize the actual mechanism of the airflow. The above-mentioned technique expresses the turbulent kinetic energy (TKE) in its result to demonstrate the real mechanism of the airflow. Apart from that, key result such as wall shear stress (WSS) can be revealed via turbulent kinetic energy (TKE) and turbulent energy dissipation (TED), where it can be suggestive of wall injury and collapsibility tissue to the HUA.

Functional respiratory imaging of the airways in the acute respiratory distress syndrome

BACKGROUND

Alveolar flooding and airway obstruction are present in the acute respiratory distress syndrome. The impact of positive end-expiratory pressure on regional airway aeration has not been described.

AIM

To assess bronchial and lung recruitment and distension during an incremental positive end-expiratory pressure trial in patients with acute respiratory distress syndrome.

METHODS

Six patients underwent lung and airway imaging at four positive end-expiratory pressure levels in a cohort trial. Images were post-processed by means of Functional Respiratory Imaging. This technique offers 3-dimensional visualisation and quantification of patients' airway and lung geometry on a regional level.

RESULTS

With increasing positive end-expiratory pressure from 0 to 20 cmH₂O, the median bronchial recruitment was 151% and the median bronchial distension 43%. Non-aerated lower lobes bronchi had more bronchial volume increase at high positive end-expiratory pressure than partially aerated upper lobes bronchi. Lung recruitment tended to be higher in patients with non-focal acute respiratory distress syndrome. In two patients, bronchial volume increase at high positive end-expiratory pressure largely exceeded bronchial volume increase observed in matched healthy control subjects at total lung capacity, suggesting severe bronchial over-distension.

CONCLUSIONS

In early acute respiratory distress syndrome, Functional Respiratory Imaging gives an innovative insight into the relationship between positive end-expiratory pressure-induced bronchial distension and recruitment, positive end-expiratory pressure-induced lung recruitment and hyperinflation and lung morphology.

Primary site identification in children with obstructive sleep apnea by computational fluid dynamics analysis of the upper airway

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is a respiratory disorder caused by the obstruction of the upper airway during sleep. The identification of the primary site of OSA is essential to determine treatment strategy. This study aimed to establish computational fluid dynamics (CFD) analysis for determining the clinical severity of OSA and the primary site of OSA.

METHODS

Twenty children (mean age, 6 years) were divided into OSA and control groups according to their apnea-hypopnea index. Three-dimensional airways were constructed from computed tomography data. The pharyngeal airway morphology and the pressure and velocity of the upper airway were evaluated using CFD analysis.

RESULTS

The maximum velocity and negative pressure of the upper airway in the OSA group were significantly correlated with the severity of OSA (r_s = .741, P < .001; r_s = -.653, P = .002). A velocity higher than 12 m/s indicated the primary site of OSA. In addition, we found that the primary site of OSA is not necessarily the same as the collapsible conduit site.

CONCLUSIONS

CFD analysis allows both the evaluation of the disease severity of OSA and the identification of the primary site of OSA in children. The primary site of OSA is not necessarily the same as the collapsible conduit site; therefore, CFD analysis can be used to identify the appropriate intervention for treating OSA.

Evaluation of human obstructive sleep apnea using computational fluid dynamics

Obstructive sleep apnea (OSA) severity might be correlated to the flow characteristics of the upper airways. We aimed to investigate the severity of OSA based on 3D models constructed from CT scans coupled with computational fluid dynamics (CFD) simulations. The CT scans of seven adult patients diagnosed with OSA were used to reconstruct the 3D models of the upper airways and CFD modeling and analyses were performed. Results from the fluid simulations were compared with the apnea-hypopnea index. Here we show a correlation between a CFD-based parameter, the adjusted pressure coefficient (Cp*), and the respective apnea-hypopnea index (Pearson's r = 0.91, p = 0.004), which suggests that the anatomical-based model coupled with CFD could provide functional and localized information for different regions of the upper airways.

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.

Retropalatal Cross-Sectional Area Is Predictive of Obstructive Sleep Apnea in Patients With Syndromic Craniosynostosis

OBJECTIVE

There is a high rate of obstructive sleep apnea (OSA) in patients with syndromic craniosynostosis (SCS). Little is known about the airway anatomy in this population. The purpose of this study is to characterize the 3 dimensional (3D) upper airway in patients with SCS with and without OSA.

DESIGN

This is a retrospective study of patients with SCS treated at Boston Children's Hospital from 2000 to 2015. Patients were divided into OSA and no-OSA groups based on polysomnography. Predictor variables included age, sex, body mass index (BMI), and 3D upper airway measurements. The primary outcome variable was the presence or absence of OSA. Secondary outcome variables were apnea-hypopnea index and oxygen saturation nadir. Descriptive and bivariate statistics were computed, and significance was set as P < .05.

RESULTS

There were 24 patients: 16 in the OSA group and 8 in the no-OSA group. The 2 groups did not differ significantly by age, BMI, or syndromic diagnosis. The presence of OSA was associated with a smaller minimum retropalatal cross-sectional area (minRPCSA; P < .001). In a logistic regression model controlling for age, sex, and upper airway length, minRPCSA was the primary predictor of OSA (P ≤ .002). Receiver operating characteristic analysis determined minRPCSA = 55.3 mm² to be the optimal diagnostic threshold for OSA, with sensitivity = 100% and specificity = 87.5% (P < .001).

CONCLUSION

A minRPCSA ≤55.3 mm² is predictive of the presence of OSA in patients with SCS.

A review of fluid-structure interaction simulation for patients with sleep related breathing disorders with obstructive sleep

Obstructive sleep apnea is one of the most common breathing disorders. Undiagnosed sleep apnea is a hidden health crisis to the patient and it could raise the risk of heart diseases, high blood pressure, depression and diabetes. The throat muscle (i.e., tongue and soft palate) relax narrows the airway and causes the blockage of the airway in breathing. To understand this phenomenon computational fluid dynamics method has emerged as a handy tool to conduct the modeling and analysis of airflow characteristics. The comprehensive fluid-structure interaction method provides the realistic visualization of the airflow and interaction with the throat muscle. Thus, this paper reviews the scientific work related to the fluid-structure interaction (FSI) for the evaluation of obstructive sleep apnea, using computational techniques. In total 102 articles were analyzed, each article was evaluated based on the elements related with fluid-structure interaction of sleep apnea via computational techniques. In this review, the significance of FSI for the evaluation of obstructive sleep apnea has been critically examined. Then the flow properties, boundary conditions and validation of the model are given due consideration to present a broad perspective of CFD being applied to study sleep apnea. Finally, the challenges of FSI simulation methods are also highlighted in this article.

Evolution of obstructive sleep apnea syndrome, nasal flow and systolic pressure of the pulmonary artery in children with indication for adenoidectomy and/or tonsillectomy over 18 months

BACKGROUND

Obstructive sleep apnea syndrome in childhood has aroused great interest due to its cardiovascular repercussions and its adverse effects on the quality of life of the affected individuals. However, fundamental aspects of the syndrome remain unknown.

OBJECTIVE

Herein we prospectively assessed pulmonary artery systolic pressure (PASP) and nasal flow in children with obstructive oral breathing with an indication for adenoidectomy and/or tonsillectomy and their relationship to the obstructive apnea and hypopnea index (OAHI).

METHODS

Twenty-one children were evaluated at the time of the surgical indication (T0) and 18 months later (T1). Polysomnography, and rhinomanometry data were collected when we evaluated PASP.

RESULTS

Among the 21 children, 13 (61.9%) presented an altered OAHI at T0. Fourteen children (66.7%) underwent surgery. Of these, nine (64.3%) had an altered OAHI at T0 and seven (50.0%) at T1. Of the seven non-operated children, four (57.1%) had an altered OAHI at T0 and two (33.3%) at T1. Mean nasal flow increased in both groups independently of surgery (p- ≤ 0.001). PASP exhibited a significant reduction between T0 and T1 in the operated group (p ≤ 0.001). OAHI of the operated group did not show a significant decrease over time (p = 0.074). In the non-operated children, the average nasal flow increased (p < 0.001), the PASP values did not reduce (p = 0.99), and the OAHI increased and then decreased over time (p = 0.025).

CONCLUSION

PASP decreased significantly and OAHI did not normalize in the operated group. Mean nasal airflow increased in the operated and non-operated groups.

The role of upper airway morphology in apnea versus hypopnea predominant obstructive sleep apnea patients: an exploratory study

OBJECTIVE

The objective of this study was to investigate the association between upper airway morphology and apnea vs hypopnea predominance in patients with obstructive sleep apnea (OSA) syndrome.

METHODS

A retrospective study on consecutively CT scans obtained from 54 OSA patients and 53 non-snoring controls. CT scans were measured to evaluate upper airway and surrounding structures' morphologic characteristics. OSA patients (matched for age, gender and body mass index) compared as two groups; apneic group: apnea ratio >50% and hypopneic group: hypopnea ratio >50%. Morphologic characteristics were analyzed using Kruskal-Wallis test and Pearson's correlation test.

RESULTS

Apneic group (17 patients) showed 76.56% apnea rate and hypopneic group (37 patients) showed 78.46% hypopnea rate. Minimal lateral and anteroposterior dimensions of velopharynx in the apneic group (0.86 ± 0.73 and 0.21 ± 0.13 cm, respectively) was statistically lesser from that of the hypopneic group (1.2 ± 0.42 and 0.54 ± 0.22 cm, respectively). Minimum cross-sectional area of the velopharynx was also lesser in apneic group (0.21 ± 0.16 cm²) than that in hypopneic group (0.65 ± 0.38 cm²). Almost all upper airway parameters in both apneic and hypopneic groups were tended to be smaller than in controls.

CONCLUSION

Decrease in airway volume does not signify the type of respiratory event, but significant narrowing of velopharynx in both dimensions; thus having the narrowest value below a certain level causes more apnea. Advances in knowledge: We did not find a similar study when we did a literature search, showing the relationship of apnea vs hypopnea predominance and upper airway parameters in CT in patients with OSA.

The Role of Functional Respiratory Imaging in Treatment Selection of Children With Obstructive Sleep Apnea and Down Syndrome

STUDY OBJECTIVES

The complexity of the pathogenesis of obstructive sleep apnea (OSA) in children with Down syndrome (DS) is illustrated by a prevalence of residual OSA after adenotonsillectomy. The aim of this study was to investigate whether upper airway imaging combined with computation fluid dynamics could characterize treatment outcome after adenotonsillectomy in these children.

METHODS

Children with DS and OSA were prospectively included. All children underwent an evaluation of the upper airway and an ultra-low dose computed tomography scan of the upper airway before adenotonsillectomy. The upper airway tract was extracted from the scan and combined with computational fluid dynamics. Results were evaluated using control polysomnography after adenotonsillectomy.

RESULTS

Thirty-three children were included: 18 boys, age 4.3 ± 2.3 years, median body mass index z-score 0.6 (-2.9 to 3.0), and median obstructive apnea-hypopnea index was 15.7 (3-70) events/h. The minimal upper airway cross-sectional area was significantly smaller in children with more severe OSA (P = .03). Nineteen children underwent a second polysomnography after adenotonsillectomy. Seventy-nine percent had persistent OSA (obstructive apneahypopnea index > 2 events/h). A greater than 50% decrease in obstructive apnea-hypopnea index was observed in 79% and these children had a significantly higher volume of the regions below the tonsils.

CONCLUSIONS

This is the first study to characterize treatment outcome in children with DS and OSA using computed tomography upper airway imaging. At baseline, children with more severe OSA had a smaller upper airway. Children with a less favorable response to adenotonsillectomy had a smaller volume of regions below the tonsils, which could be due to enlargement of the lingual tonsils, glossoptosis, or macroglossia.

COMMENTARY

A commentary on this article appears in this issue on page 501.

The Finite Element Simulation of the Upper Airway of Patients with Moderate and Severe Obstructive Sleep Apnea Hypopnea Syndrome

Objectives

To investigate the snoring modes of patients with Obstructive Sleep Apnea Hypopnea Syndrome and to discover the main sources of snoring in soft tissue vibrations.

Methods

A three-dimensional finite element model was developed with SolidEdge to simulate the human upper airway. The inherent modal simulation was conducted to obtain the frequencies and the corresponding shapes of the soft tissue vibrations. The respiration process was simulated with the fluid-solid interaction method through ANSYS.

Results

The first 6 orders of modal vibration were 12 Hz, 18 Hz, 21 Hz, 22 Hz, 36 Hz, and 39 Hz. Frequencies of modes 1, 2, 4, and 5 were from tongue vibrations. Frequencies of modes 3 and 6 were from soft palate vibrations. Steady pressure distribution and air distribution lines in the upper airway were shown clearly in the fluid-solid interaction simulation results.

Conclusions

We were able to observe the vibrations of soft tissue and the modeled airflow by applying the finite element methods. Future studies could focus on improving the soft tissues vibration compliances by adjusting the model parameters. Additionally, more attention should be paid to vibrational components below 20 Hz when performing an acoustic analysis of human snore sounds due to the presence of these frequencies in this model.

Predicting the effect of treatment in paediatric OSA by clinical examination and functional respiratory imaging

OBJECTIVE

The aim of this study was to investigate whether functional respiratory imaging (FRI) or clinical examination could predict treatment outcome for obstructive sleep apnea (OSA) in normal-weight, non-syndromic children.

METHODS

Normal weight children diagnosed with OSA by polysomnography were prospectively included. All children got a thorough evaluation and an ultra-low dose computed tomography scan of the upper airway (UA). A 3-D reconstruction was built combined with computational fluid dynamics for FRI. Decisions on the need and type of surgery were based upon findings during drug-induced sleep endoscopy. A second polysomnography was performed 3-12 months after surgery.

RESULTS

Ninety-one children were included: 62 boys, 5.0 ± 2.7 years, and BMI z-score of -0.1 ± 1.2. Children with more severe OSA had a smaller volume of the overlap region between the adenoids and tonsils. Nineteen out of 60 patients had persistent OSA (oAHI >2/h). A lower conductance in the UA and a higher tonsil score predicted successful treatment.

CONCLUSIONS

A less constricted airway, as characterized by both FRI and a lower tonsil score, was associated with a less favorable response to (adeno) tonsillectomy. Further studies after treatment using FRI and DISE are warranted to further characterize the UA of these subjects.

The incompressibility assumption in computational simulations of nasal airflow

Most of the computational works on nasal airflow up to date have assumed incompressibility, given the low Mach number of these flows. However, for high temperature gradients, the incompressibility assumption could lead to a loss of accuracy, due to the temperature dependence of air density and viscosity. In this article we aim to shed some light on the influence of this assumption in a model of calm breathing in an Asian nasal cavity, by solving the fluid flow equations in compressible and incompressible formulation for different ambient air temperatures using the OpenFOAM package. At low flow rates and warm climatological conditions, similar results were obtained from both approaches, showing that density variations need not be taken into account to obtain a good prediction of all flow features, at least for usual breathing conditions. This agrees with most of the simulations previously reported, at least as far as the incompressibility assumption is concerned. However, parameters like nasal resistance and wall shear stress distribution differ for air temperatures below [Formula: see text]C approximately. Therefore, density variations should be considered for simulations at such low temperatures.

Three-dimensional analysis of craniofacial bones and soft tissues in obstructive sleep apnea using cone beam computed tomography

A total of 154 adult patients with sleep complaints underwent a polysomnography and a craniofacial cone beam computed tomography (CBCT). OSA was defined as an apnea and hypopnea index (AHI) or an oxygen desaturation index (ODI) ≥ 10. Soft tissues and craniofacial bones volumes were prospectively measured by CBCT and collected blindly from sleep polysomnography. Among the study patients, 127 (83%) suffered from OSA and 27 (17%) did not. OSA patients demonstrated a narrower maxillo-palatine core volume (11.7±3.2 vs 14.6±4.9cm³) even when adjusting for age, gender, height, neck circumference and body mass index. These upper airway measures provide a comprehensive analysis of bony structures and soft tissues, which can be involved in OSA.

Obstructive sleep disordered breathing in 2- to 18-year-old children: diagnosis and management

This document summarises the conclusions of a European Respiratory Society Task Force on the diagnosis and management of obstructive sleep disordered breathing (SDB) in childhood and refers to children aged 2-18 years. Prospective cohort studies describing the natural history of SDB or randomised, double-blind, placebo-controlled trials regarding its management are scarce. Selected evidence (362 articles) can be consolidated into seven management steps. SDB is suspected when symptoms or abnormalities related to upper airway obstruction are present (step 1). Central nervous or cardiovascular system morbidity, growth failure or enuresis and predictors of SDB persistence in the long-term are recognised (steps 2 and 3), and SDB severity is determined objectively preferably using polysomnography (step 4). Children with an apnoea-hypopnoea index (AHI) >5 episodes·h(-1), those with an AHI of 1-5 episodes·h(-1) and the presence of morbidity or factors predicting SDB persistence, and children with complex conditions (e.g. Down syndrome and Prader-Willi syndrome) all appear to benefit from treatment (step 5). Treatment interventions are usually implemented in a stepwise fashion addressing all abnormalities that predispose to SDB (step 6) with re-evaluation after each intervention to detect residual disease and to determine the need for additional treatment (step 7).

Computational fluid dynamics endpoints for assessment of adenotonsillectomy outcome in obese children with obstructive sleep apnea syndrome

BACKGROUND

Improvements in obstructive sleep apnea syndrome (OSAS) severity may be associated with improved pharyngeal fluid mechanics following adenotonsillectomy (AT). The study objective is to use image-based computational fluid dynamics (CFD) to model changes in pharyngeal pressures after AT, in obese children with OSAS and adenotonsillar hypertrophy.

METHODS

Three-dimensional models of the upper airway from nares to trachea, before and after AT, were derived from magnetic resonance images obtained during wakefulness, in a cohort of 10 obese children with OSAS. Velocity, pressure, and turbulence fields during peak tidal inspiratory flow were computed using commercial software. CFD endpoints were correlated with polysomnography endpoints before and after AT using Spearman׳s rank correlation (rs).

RESULTS

Apnea hypopnea index (AHI) decreases after AT was strongly correlated with reduction in maximum pressure drop (dPTAmax) in the region where tonsils and adenoid constrict the pharynx (rs=0.78, P=0.011), and with decrease of the ratio of dPTAmax to flow rate (rs=0.82, P=0.006). Correlations of AHI decrease to anatomy, negative pressure in the overlap region (including nasal flow resistance), or pressure drop through the entire pharynx, were not significant. In a subgroup of subjects with more than 10% improvement in AHI, correlations between flow variables and AHI decrease were stronger than in all subjects.

CONCLUSIONS

The correlation between change in dPTAmax and improved AHI suggests that dPTAmax may be a useful index for internal airway loading due to anatomical narrowing, and may be better correlated with AHI than direct airway anatomic measurements.