Application of patient-specific simulation workflow for obstructive sleep apnea diagnosis and treatment with a mandibular advancement device

Tissue-specified reconstruction modeling of the head and neck structure and its application in simulating airway obstruction

Background and objective

Three-dimensional (3D) reconstruction of head and neck tissues has extensive clinical applications, but due to the complexity and variability of tissue structure, there is still a lack of a complete scheme to reconstruct the head and neck tissues. This study aims to establish a tissue-specified multi-directional cross-sectional image sequence construction method to capture diverse tissue contour information.

Methods

The image sequences that are most conducive to acquiring the boundary contours of the target tissue are constructed from 3D MRI images of the head and neck in a non-traditional way based on the characteristics of each target tissue, and an effective registration strategy is used to integrate the boundaries of the target tissue segmented from multiple image sequences. The NURBS (Non-Uniform Rational B-Splines) surface modeling method is used to construct the 3D structure of the head and neck based on the segmented tissue boundaries, and then the constructed structure is used to build a fluid-structure interaction model to simulate airway collapse.

Results

The multi-directional cross-sectional image sequences of head and neck tissues were reconstructed, which successfully supplemented the missing boundary information in unidirectional image sequences commonly used in anatomical reconstructions. The boundaries of the tongue and soft palate were obtained from three corresponding sequential images respectively, and nonlinear registration methods were developed to match the intersections of the target tissue boundaries segmented from different image sequences. The complete 3D head and neck structure, including the surrounding tissues of the upper airway, was accurately reconstructed, and then directly converted into a finite element model through a meshing procedure. The head and neck numerical models successfully simulate airway collapse in both the obstructive sleep apnea patient and the normal subject, providing detailed information on soft tissue deformation and predicting the values of the airway critical closing pressure.

Conclusions

A complete 3D reconstruction scheme from multi-directional image sequence construction to nonlinear boundary registration and NURBS surface generation is established. The constructed model can accurately reflect the characteristics of real anatomical structure, and can be directly used for complex numerical simulations of upper airway collapse.

Transoral Drug-Induced Sleep Endoscopy: A Useful Complementary Tool in Sleep Surgery

Introduction  Drug-induced sleep endoscopy (DISE) is performed widely, and several studies have demonstrated its validity as it provides clinical information not available by routine clinical inspection alone. Objective  This study aims to evaluate the role of transoral drug-induced sleep endoscopy (DISE) in the evaluation of tongue-palate (TP) interaction and its impact on surgical outcomes. Methods  A total of 42 patients with known obstructive sleep apnea syndrome (OSAS) were classified into two groups according to TP interaction (the absence of space between tongue and palate with the visual impression that the tongue is pushing the soft palate) into +ve and -ve TP interaction. Snoring according to the visual analogue scale (VAS), the Epworth Sleepiness Scale (ESS), and sleep study data were recorded before and after the pharyngoplasty operation. Results  There was a statistically significant difference between studied groups postoperative regarding minimal oxygen saturation, snoring index, apnea-hypopnea index (AHI), the ESS, and visual analogue scale of snoring ( p  = 0.003*, p  < 0.001*, p  < 0.001*, p  = 0.004*, and p  = 0.003*, respectively). It displayed a marked higher average improvement among cases with -ve than in those with +ve TP interaction in terms of snoring index, AHI, and ESS. Conclusion  The Transoral DISE Has A Valuable Role In Evaluating And Assessing TP Interaction And Its Importance On Surgical Outcomes. Cases With Positive TP Interaction Show Poor Response To Isolated Palatopharyngeal Expansion And Need Further Analysis To Create A Better Treatment Plan And Improve Outcomes.

A systematic review on 4D images of the upper airway in patients with OSA

AIM-BACKGROUND

In the treatment of obstructive sleep apnoea (OSA), oral appliances are now being recognized as a valuable alternative to continuous positive airway pressure (CPAP). Various static imaging techniques of the upper airways allow for assessment of bone and soft tissue structures. However, static images do not capture dynamic airway characteristics. The aim of this paper was to review 4D imaging techniques in patients with OSA.

METHODS

PubMed/MEDLINE, Web of Science and Embase were systematically searched for studies published before June 2022. The review was compliant with the PRISMA guidelines. The quality of each eligible study was critically evaluated by all four authors independently. Four unique articles with qualitative analyses were retrieved. All included studies had a clear objective/aim, an appropriate endpoint and sufficiently described eligibility criteria.

RESULTS

With dynamic imaging (4D) evaluation of the upper airway, the incidence of upper airway collapsibility due to use of a mandibular advancement device (MAD) was reduced, extraluminal tissue pressure was decreased and the space in the upper airway was increased, notably in the retropalatal and retroglossal areas of the airway. These findings suggest that MADs may be effective for OSA regardless of whether or not the obstruction site is in the velopharynx or oropharynx. However, further investigation of dynamic changes in the upper airway is required to explain the efficacy of OSA treatment and the underlying mechanisms.

Potential of computational models in personalized treatment of obstructive sleep apnea: a patient-specific partial 3D finite element study

The upper airway experiences mechanical loads during breathing. Obstructive sleep apnea is a very common sleep disorder, in which the normal function of the airway is compromised, enabling its collapse. Its treatment remains unsatisfactory with variable efficacy in the case of many surgeries. Finite element models of the upper airway to simulate the effects of various anatomic and physiologic manipulations on its mechanics could be helpful in predicting surgical success. Partial 3D finite element models based on patient-specific CT-scans were undertaken in a pilot study of 5 OSA patients. Upper airway soft tissues including the soft palate, hard palate, tongue, and pharyngeal wall were segmented around the midsagittal plane up to a width of 2.5 cm in the lateral direction. Simulations of surgical interventions such as Uvulopalatopharyngoplasty (UPPP), maxillo-mandibular advancement (MMA), palatal implants, and tongue implants have been performed. Our results showed that maxillo-mandibular advancement (MMA) surgery of 1 cm improved the critical closing pressure by at least 212.2%. Following MMA, the best improvement was seen via uvulopalatopharyngoplasty (UPPP), with an improvement of at least 19.12%. Palatal and tongue implants also offered a certain degree of improvement. Further, we observed possible interacting mechanisms that suggested simultaneous implementation of UPPP and tongue stiffening; and palatal and tongue stiffening could be beneficial. Our results suggest that computational modeling is a useful tool for analyzing the influence of anatomic and physiological manipulations on upper airway mechanics. The goal of personalized treatment in the case of OSA could be achieved with the use of computational modeling.

The use of CBCT in orthodontics with special focus on upper airway analysis in patients with sleep-disordered breathing

Applications of cone-beam CT (CBCT) in orthodontics have been increasingly discussed and evaluated in science and practice over the last two decades. The present work provides a comprehensive summary of current consolidated practice guidelines, cutting-edge innovative applications, and future outlooks about potential use of CBCT in orthodontics with a special focus on upper airway analysis in patients with sleep-disordered breathing. The present scoping review reveals that clinical applications of CBCT in orthodontics are broadly supported by evidence for the diagnosis of dental anomalies, temporomandibular joint disorders, and craniofacial malformations. On the other hand, CBCT imaging for upper airway analysis-including soft tissue diagnosis and airway morphology-needs further validation in order to provide better understanding regarding which diagnostic questions it can be expected to answer. Internationally recognized guidelines for CBCT use in orthodontics are existent, and similar ones should be developed to provide clear indications about the appropriate use of CBCT for upper airway assessment, including a list of specific clinical questions justifying its prescription.

Computational Rhinology: Unraveling Discrepancies between In Silico and In Vivo Nasal Airflow Assessments for Enhanced Clinical Decision Support

Computational rhinology is a specialized branch of biomechanics leveraging engineering techniques for mathematical modelling and simulation to complement the medical field of rhinology. Computational rhinology has already contributed significantly to advancing our understanding of the nasal function, including airflow patterns, mucosal cooling, particle deposition, and drug delivery, and is foreseen as a crucial element in, e.g., the development of virtual surgery as a clinical, patient-specific decision support tool. The current paper delves into the field of computational rhinology from a nasal airflow perspective, highlighting the use of computational fluid dynamics to enhance diagnostics and treatment of breathing disorders. This paper consists of three distinct parts-an introduction to and review of the field of computational rhinology, a review of the published literature on in vitro and in silico studies of nasal airflow, and the presentation and analysis of previously unpublished high-fidelity CFD simulation data of in silico rhinomanometry. While the two first parts of this paper summarize the current status and challenges in the application of computational tools in rhinology, the last part addresses the gross disagreement commonly observed when comparing in silico and in vivo rhinomanometry results. It is concluded that this discrepancy cannot readily be explained by CFD model deficiencies caused by poor choice of turbulence model, insufficient spatial or temporal resolution, or neglecting transient effects. Hence, alternative explanations such as nasal cavity compliance or drag effects due to nasal hair should be investigated.

Long-term evaluation of treatment protocols for isolated midfacial fractures in a German nation-wide craniomaxillofacial trauma center 2007-2017

An update on the trends in maxillofacial traumatology provides additional information on the actual and changing needs. This retrospective study aimed to review all patient records of patients treated for isolated midface fractures in the Department of Cranial- and Maxillofacial Surgery at the Dortmund General Hospital between 2007 and 2017. The patient radiographs and patient files were reviewed. The safety and efficacy of the applied methods were controlled by assessing complications based on the Clavien-Dindo classification system. The statistical analysis included descriptive methods including regression analysis and χ2-test. In eleven years, 3474 isolated midface fracture sites have been identified in 2868 patients. The yearly trend is slightly increasing, in elderly clearly worsening, in children and youth decreasing. The male-to-female ratio was 2.16:1 for the whole study population, in the age group 18-25 y.o. 6.95:1 while in elderly above 80 y.o. 1:2.51, the age group specific incidence reflects this result, too. The most common fractures were nasal bone fractures (1405), zygomatic fractures (832) and orbital floor fractures (700). The average hospital stay was 2.7 days, the most fractures were operated within 24 h. The complication rate was 2.02% (Clavien-Dindo class II-V). The incidence of midfacial fractures is increasing in the total population and especially in elderly, but decreasing in children. Development of injury prevention measures is needed in this population. The diagnostic and therapeutic procedures are appropriate, as there is a low complication rate and short inpatient stay observed.

Experimental study on the influence of model variations on the airway occlusion of an obstructive sleep apnea patient

This study deals with the analysis of model parameters to mimic the airway collapse of an obstructive sleep apnea patient during nasal breathing. Different material properties and geometry variations of a patient-specific airway model are analyzed in detail. The patient-specific airway geometry is obtained from MRI data. A completely rigid model is compared to two partly elastic variations with different elasticities. Furthermore, the influence of the nasal cavities and the treatment effect of a mandibular protrusion are studied. Rigid model parts are 3D-printed and elastic parts cast from silicone. The models are analyzed under the impact of a transient airflow which is realized through a computer controlled piston pump. The results suggest, that, for moderate deformations, the elasticity of the soft tissue replicate influences rather the level of the pressure drop inside the airway than the shape of the pressure curve. The same suggestion can be made for the influence of the nasal cavities. Often, the spatial location of the minimum pressure is taken as the collapse site of the airway geometry. This study demonstrates, that the spatial locations of the minimum pressure and the maximum deformation do not match. This reveals the importance of a coupled approach of soft tissue and airflow analysis in the search of the collapse site and therefore the best treatment option. A treatment effect of the mandibular protrusion can be anticipated with an accurate patient-specific airway model.