Analysis of Velopharyngeal Functions Using Computational Fluid Dynamics Simulations

Construction of virtual airway model to assist surgical correction of velopharyngeal insufficiency with posterior pharyngeal flap

OBJECTIVE

Posterior pharyngeal flap (PPF) is one of the most common surgical technique to correct velopharyngeal insufficiency(VPI), during which controlling the sizes of the lateral pharyngeal ports(LPP) is the key to outcomes. One innovative procedure was developed to well control the size of LPP.

MATERIALS AND METHODS

40 patients with repaired cleft palate were collected from June 2022 to August 2023. All patients were diagnosed with VPI, and treated with modified PPF surgery. For each patient, upper airway model was reconstructed, and the virtual airway model of PPF was designed. The nasal valve area was measured as it was considered to be the narrowest part of the upper airway. The upper airway resistances under different sizes of LPP was predicted through computational fluid dynamics analysis. The minimum size of each lateral pharyngeal port without obviously increase of upper airway resistance was calculated through effect of lateral pharyngeal ports' size on upper airway resistance. Postoperative follow-up was 6-18 months, including speech outcome and respiration outcome. Resting soft palate length (RVL), effective working length of soft palate (EWL) and angle of soft palate elevation (AVL) were measured and compared according to the lateral cephalometric radiograph.

RESULTS

There was a linear relationship between the threshold value and nasal valve (R = 0.62). Among the forty patients, the average size of nasal valve was 47.81 mm2, the average size of the threshold value of LPP was 31.63mm2. The proportion of velopharyngeal closure competence after surgery was 95 %. Compared with the preoperative measurements, there were significantly increase of RVL, EWL and AVL (P < 0.05). There were significantly difference in the nasal obstruction symptom evaluation score in long-term follow-up compared to short-term follow-up (P < 0.05), and no one needed flap revision. There was no significant difference in nasal respiration and nasal resistance before and after surgery (P > 0.05).

CONCLUSION

With the help of computer fluid dynamics analysis, it is possible to predict the threshold size of lateral pharyngeal port without obviously increasing upper airway resistance and reduce the risk of suffering from airway obstruction for patients undergoing PPF surgery.

ChatGPT for shaping the future of dentistry: the potential of multi-modal large language model

The ChatGPT, a lite and conversational variant of Generative Pretrained Transformer 4 (GPT-4) developed by OpenAI, is one of the milestone Large Language Models (LLMs) with billions of parameters. LLMs have stirred up much interest among researchers and practitioners in their impressive skills in natural language processing tasks, which profoundly impact various fields. This paper mainly discusses the future applications of LLMs in dentistry. We introduce two primary LLM deployment methods in dentistry, including automated dental diagnosis and cross-modal dental diagnosis, and examine their potential applications. Especially, equipped with a cross-modal encoder, a single LLM can manage multi-source data and conduct advanced natural language reasoning to perform complex clinical operations. We also present cases to demonstrate the potential of a fully automatic Multi-Modal LLM AI system for dentistry clinical application. While LLMs offer significant potential benefits, the challenges, such as data privacy, data quality, and model bias, need further study. Overall, LLMs have the potential to revolutionize dental diagnosis and treatment, which indicates a promising avenue for clinical application and research in dentistry.

Inspiration After Posterior Pharyngeal Flap Palatoplasty: A Preliminary Study Using Computational Fluid Dynamic Analysis

Posterior pharyngeal flap palatoplasty (PPF) is one of the most commonly used surgical procedures to correct speech, especially for patients suffering from velopharyngeal insufficiency (VPI). During PPF, surgeons use the catheter to control the lateral velopharyngeal port on each side. Airway obstruction and sleep apnea are common after PPF. To understand the air dynamics of the upper airway after PPF, we used computational fluid dynamics (CFD) to demonstrate the airflow. In our previous study, we have revealed the expiration process of the upper airway after PPF and shown the features of how PPF successfully restores the oral pressure for speech. In this study, we focus on examining the inspiration process. Normal airway structures were included. For the normal velopharyngeal structure, one cylinder was applied to each model. For recapitulating the velopharyngeal structure after PPF, two cylinders were used in each model. The ports for borderline/inadequate closure, which can help the oral cavity get the required pressure, were chosen for this study. A real-time CFD simulation was used to capture the airflow through the ports. We found that the airflow dynamics of the upper airway's inspiration were dependent on the velopharyngeal structure. Although the airflow patterns were similar, the velocities between one-port and two-port structures were different, which explained why patients after PPF breathed harder than before and suggested that the one-port structure might be a better choice for secondary VPI reconstruction based on the CFD analyses.

Airflow of the Two-Port Velopharyngeal Closure: Study Using Computational Fluid Dynamics

Posterior pharyngeal flap palatoplasty is used to restore the function of velopharyngeal (VP) closure, after which 2 ports remain between the nasal and oral cavity. The authors hypothesized that the airflow dynamics of the upper airway is different in PPF patients compared to health subjects, who only has 1 movable port. Twenty adults who have multislice spiral computed tomography scan were included in this study. Two cylinders (radius, 2.00 mm; height, 4.5 mm) were used to recapitulate the 2-port VP structure after PPF palatoplasty. The areas of ports were modified by changing the radius of 2 cylinders. Real-time computational fluid dynamics simulation was used to capture the airflow velocity and pressures through the 2 ports. The airflow velocity and pressure of upper airway were recorded as the total areas of 2 VP ports increased. The total orifice areas of the 2-port VP closure for 4 VP conditions, including adequate closure, adequate/borderline closure, borderline/inadequate closure, and inadequate closure, were demonstrated. Significant differences between the 2-port VP function for demonstrating PPF reconstruction and the 1-port VP function were found. Airflow dynamics is dependent on the VP structure. The 2-port airflow model for mimicking VP closure after PPF palatoplasty demonstrated airflow characteristics that were significantly different from the 1-port model in normal VP closure.

Computational technology for nasal cartilage-related clinical research and application

Surgeons need to understand the effects of the nasal cartilage on facial morphology, the function of both soft tissues and hard tissues and nasal function when performing nasal surgery. In nasal cartilage-related surgery, the main goals for clinical research should include clarification of surgical goals, rationalization of surgical methods, precision and personalization of surgical design and preparation and improved convenience of doctor-patient communication. Computational technology has become an effective way to achieve these goals. Advances in three-dimensional (3D) imaging technology will promote nasal cartilage-related applications, including research on computational modelling technology, computational simulation technology, virtual surgery planning and 3D printing technology. These technologies are destined to revolutionize nasal surgery further. In this review, we summarize the advantages, latest findings and application progress of various computational technologies used in clinical nasal cartilage-related work and research. The application prospects of each technique are also discussed.

Computational Fluid Dynamic Analysis of Different Velopharyngeal Closure Patterns

Objective:

Velopharyngeal (VP) closure has high impact on the quality of life, especially in patients with cleft palate. For better understanding the VP closure, it is important to understand the airflow dynamics of different closure patterns, including circular, coronal, sagittal, and circular with a Passavant’s ridge. The purpose of this study was to demonstrate the airflow characteristics of different velopharyngeal closure patterns.

Methods:

Sixteen adults with no notable upper airway abnormality who needed multislice spiral computed tomography scans as part of their clinical care. Airways were reconstructed. A cylinder and a cuboid were used to replace the VP port in three models of VP port patterns. Flow simulations were carried using computational fluid dynamics. Airflow pressures in the VP orifice, oral cavity and nasal cavity, as well as airflow velocity through the velopharyngeal orifice, were calculated.

Results:

The airflow dynamics at the velopharynx were different among different velopharyngeal patterns as the area of the velopharyngeal port increased from 0 to 25 mm2. The orifice areas of different closure conditions in four velopharyngeal closure patterns were significantly different. The maximal orifice area for adequate velopharyngeal closure was 7.57 mm2 in the coronal pattern and 6.21 mm2 in the sagittal pattern.

Conclusions:

Airflow dynamics of the velopharynx were correlated to the velopharyngeal closure patterns. Different closure patterns had different largest permitted orifice areas for getting the appropriate oral pressures for normal speech.