The Virtual Pediatric Airways Workbench

The Virtual Pediatric Airways Workbench (VPAW) is a patient-centered surgical planning software system targeted to pediatric patients with airway obstruction. VPAW provides an intuitive surgical planning interface for clinicians and supports quantitative analysis regarding prospective surgeries to aid clinicians deciding on potential surgical intervention. VPAW enables a full surgical planning pipeline, including importing DICOM images, segmenting the airway, interactive 3D editing of airway geometries to express potential surgical treatment planning options, and creating input files for offline geometric analysis and computational fluid dynamics simulations for evaluation of surgical outcomes. In this paper, we describe the VPAW system and its use in one case study with a clinician to successfully describe an intended surgery outcome

Pediatric sleep-related breathing disorders: advances in imaging and computational modeling

We understand now that sleep of sufficient length and quality is required for good health. This is particularly true for infants and children, who have the added physiologic task of growth and development, as compared to their adult counterparts. Sleep-related breathing disorders (SRBDs) are common in childhood and if unrecognized and not treated can result in significant morbidity. For example, children with obstructive sleep apnea (OSA) can exhibit behavioral, mood, and learning difficulties. If left untreated, alterations in the function of the autonomic nervous system and a chronic inflammatory state result, contributing to the risk of heart disease, stroke, glucose intolerance, and hypertension in adulthood

疾患鼻気道における空気流と粒子堆積の計算流体力学的研究

Understanding the properties of airflow in the nasal cavity is very important in determining the nasal physiology and in diagnosis of various anomalies associated with the nose. The complex anatomy of the nasal cavity has proven to be a significant obstacle in the understanding of nasal obstructive disorders. Due to their non-invasiveness, Computational Fluid Dynamics (CFD) has now been utilized to assess the effects of surgical interventions on nasal morphological changes as well as local breathing airflow characteristics through the upper airway of individual patients. Furthermore, nasal inhalation is a major route of entry into body for airborne pollutions. Therefore, the function of the upper airway to filter out the inhaled toxic particles is considered important. The determination of the total particle filtering efficiency and the precise location of the induced lesion in the upper airway is the first step in understanding the critical factors involved in the pathogenesis of the upper airway injury. The present work involved development of three-dimensional diseased upper airway models from Computed Tomographic (CT) scan images derived from a nasal airway without any nasal diseased and an upper airway which was diagnosed with chronic nasal obstruction and obstructive sleep apnea. Numerical simulation of airflow and transport and deposition of inhaled pollutant through chronic diseased nasal airway, constricted pharyngeal representing Obstructive Sleep Apnea (OSA) and diseased upper airway with OSA for pre- and post-operative cases have been studied. Detailed flow pattern and characteristics for inspiratory airflow for various breathing rates (7.5-40 L/min) were evaluated. Simulation of the particle transport and deposition of micro-sized particles with particle diameter ranging from 1-40 ?m were also investigated. In the first part of this study, the surgical treatment performed in the nasal cavity which include septoplasty, inferior turbinate reduction and partial concha bullosa resection substantially increased nasal volume, which influenced flow partitioning and decreases the pressure drop and flow resistance of the nasal passage. The removal of the obstruction in the nasal airway significantly improve the breathing quality. However, the nasal airway experienced approximately about a 50 % decrease in total particle filtering efficiency after surgery. Therefore, careful consideration should be given to this matter before nasal operation especially for a patient with breathing allergic history. In the second part of this study, the morphology of the constricted pharyngeal representing OSA was found to significantly affect the airflow pattern and the deposition fraction of microparticles. The morphology of the upper airway, the size of the inhaled particle and breathing rate was found significantly affect the total particle deposition efficiency and local deposition fraction in the upper airway. The presented regional deposition fraction may be used in specifying the site of highest possibility for respiratory lesions according to the breathing rate and the size of the inhaled toxic particles. Results obtained from this study can be also used to estimate the location of airway obstruction in upper airway of patient with sleep apnea symptom. In the third part of this study, the surgical conducted procedure has cleared out the obstructions in the nasal airway hence improve the airflow distribution through the upper airway during inhalation process. This study shows that the nasal surgery alone can help improve the breathing quality in the upper airway with OSA. The reduction of the airflow resistance in the nasal cavity affect the pressure distribution in the lower part of the upper airway. Obstruction in the nasal passage and sudden airway expansion in the upper airway increased number of particles trap, recirculated and finally deposited in the airway. Finally, the experimental data obtained from the experimental study utilizing the developed pharyngeal airway further validate the result obtained from the numerical study.九州工業大学博士学位論文 学位記番号：生工博甲第315号 学位授与年月日：平成30年3月23日1: INTRODUCTION|2: LITERATURE REVIEW|3: MODELLING THE HUMAN UPPER AIRWAY|4: NUMERICAL SIMULATION METHODOLOGY|5: NUMERICAL INVESTIGATION ON AIRFLOW CHARACTERISTICS IN NASAL CAVITY HAVING TURBINATE HYPERTROPHY, CONCHA BULLOSA, AND SEPTUM DEVIATION WITH OSA: PRE- AND POST SURGERY|6: COMPUTATIONAL FLUID DYNAMICS STUDY OF AIRFLOW AND MICROPARTICLE DEPOSITION IN A CONSTRICTED PHARYNGEAL SECTION REPRESENTING OBSTRUCTIVE SLEEP APNEA DISEASE|7: NUMERICAL SIMULATION OF AIRFLOW AND AEROSOL DEPOSITION IN REALISTIC HUMAN UPPER AIRWAY WITH OBSTRUCTIVE SLEEP APNEA AND CHRONIC NASAL OBSTRUCTION: PRE- AND POST-SURGERY|8: EXPERIMENTAL INVESTIGATION|9: CONCLUSIONS AND FUTURE RECOMMENDATIONS九州工業大学平成29年

Fluid Structure Interaction Study of the Obstructive Sleep Apnea and Surgical Treatment Using Suture-Patch Device on the Patient’s Tongue

Up to 14% of the U.S. population is estimated to have obstructive sleep apnea (OSA) related to obesity, and there is increased incidence occurring worldwide. While treatment with continuous positive airway pressure (CPAP) resolves airway obstruction, patient compliance is relatively low. Alternative interventions are available to treat OSA patients; however, their outcomes have had variable results. For example, current technologies have demonstrated an inability to define and treat the specific anatomical site(s) causing the obstruction, resulting in suboptimal modifications of the airway and poor control of OSA. In the current study, a three-dimensional (3-D) fluid-structure interaction (FSI) numerical simulation has been applied to simulate upper airway (UA) collapse, without considering the individual muscles. The objective of this study is to demonstrate how to use the two-way FSI numerical simulation to study the characteristics of and identify the precise location of an upper airway collapse on female and male patients with OSA. This task was accomplished using Simpleware®, which is medical image processing software, and ANSYS® Fluent, which is computational fluid dynamics (CFD) and structural software. Simpleware® is able to process a patient’s 3-D computed tomography (CT) scan image and render this airway image to ANSYS® Fluent in order to generate the computational domains of fluid and structure. During FSI numerical simulation, areas that are prone to collapse and precipitate apneic episodes were identified at the tip of the soft palate and the base of the tongue, with intrathoracic pressures as low as -1370 Pa. These results are consistent with anatomical structures that are currently indicated and targeted in the treatment of OSA. The negative pressure is similar to previous values reported in human esophageal pressure measurements in UA resistance syndrome. This improved two-way FSI numerical simulation, which is the first to accurately model the UA geometry in OSA, can allow virtual modification of the airway before actual clinical treatment by ear, nose, and throat (ENT) medical doctors. The improved two-way FSI numerical simulation was later used to model and simulate a unique suture-patch device, which can be used to virtually apply force to the tongue. Based on the numerical simulation results, this device can effectively reduce the risk of UA occlusion and open up the UA at the pharynx 92% of its original area under the peak inhale volume for a specific patient. This provides a possible treatment for the patient, instead of conducting tissue removal or requiring use of a CPAP mask. Three locations to put the suture-patch device on the patient’s tongue were compared in the study, and the suture-patch at location 2 is recommended. Next, the bisection method is used to find the minimum force needed to open up the airway from occlusion. The results show that 1.25 N is the recommended force. Both male and female OSA patients were studied and compared in three different aspects: geometry, flow field, and tissue movement. The results from this case study show that tissue movement does not depend only on the apnea and hypopnea index (AHI). They show that classic symptoms, like snoring, should not be the only diagnosis of OSA. Anyone with restless sleep or daytime fatigue, with snoring syndrome, should visit an ENT doctor and have a clinical sleep test in order to find out whether he or she has OSA. Using the current FSI development, a patient-specific numerical simulation can be carried out prior to surgery to virtually audit different treatments, when the patient is diagnosed with severe OSA and needs surgical treatment. Then the ENT doctor can discuss the best treatment with the patient based on the simulation results. Moreover, ENT doctors and patients will be able to visualize the outcome of virtual surgery from numerical simulations. This will give patients more confidence and help to alleviate their trepidation about treatment options. Moreover, the patient-specific numerical simulations can be used to compare different OSA cases to study the characteristics they have in common. Therefore, patients can understand more about OSA, and ENT doctors can determine the possible ways to conduct the best treatment in the near future

A matter of life and breath:Children with severe acute asthma admitted to the pediatric intensive care unit

Risk factors, treatment and psychosocial outcomes of children with severe acute asthma admitted to the pediatric intensive care unit

Development and validation of HRCT airway segmentation algorithms

Direct measurements of airway lumen and wall areas are potentially useful as a diagnostic tool and as an aid to understanding the pathophysiology underlying lung disease. Direct measurements can be made from images created by high resolution computer tomography (HRCT) by using computer-based algorithms to segment airways, but current validation techniques cannot adequately establish the accuracy and precision of these algorithms. A detailed review of HRCT airway segmentation algorithms was undertaken, from which three candidate algorithm designs were developed. A custom Windows-based software program was implemented to facilitate multi-modality development and validation of the segmentation algorithms. The performance of the algorithms was examined in clinical HRCT images. A centre-likelihood (CL) ray-casting algorithm was found to be the most suitable algorithm due to its speed and reliability in semi-automatic segmentation and tracking of the airway wall. Several novel refinements were demonstrated to improve the CL algorithm’s robustness in HRCT lung data. The performance of the CL algorithm was then quantified in two-dimensional simulated data to optimise customisable parameters such as edge-detection method, interpolation and number of rays. Novel correction equations to counter the effects of volume averaging and airway orientation angle were derived and demonstrated in three-dimensional simulated data. The optimal CL algorithm was validated with HRCT data using a plastic phantom and a pig lung phantom matched to micro-CT. Accuracy was found to be improved compared to previous studies using similar methods. The volume averaging correction was found to improve precision and accuracy in the plastic phantom but not in the pig lung phantom. When tested in a clinical setting the results of the optimised CL algorithm was in agreement with the results of other measures of lung function. The thesis concludes that the relative contributions of confounders of airway measurement have been quantified in simulated data and the CL algorithm’s performance has been validated in a plastic phantom as well as animal model. This validation protocol has improved the accuracy and precision of measurements made using the CL algorith

Computational Fluid Dynamics Study Of Nasal Cavity Model

Understanding the properties of airflow in the nasal cavity is very important in determining the nasal physiology and in diagnosis of various anomalies associated with the nose. Inter-human anatomical variation for the nasal cavity exists and also differences on physiological morphology are observed based on gender. No specific numerical modeling studies have been carried out to compare and ascertain the effect of gender on flow variable inside the nasal cavity. Also numerical modeling involves various simplifications, for example the postural effect and appropriate boundary conditions which affect the outcome of the airflow studies. The present work involves development of three-dimensional nasal cavity models using computed tomographic images of healthy Malaysian females. A steady state continuity and Navier stoke equations were solved for both inspiratory and expiratory mechanism with flow rates ranging from 7.5 to 15 L/min as laminar and 20 to 40 L/min studies were simulated depicting turbulent flow conditions. Computational fluid dynamics (CFD) analysis provided effective visualization of the flow features inside the nasal cavity. The comparison between inspiratory and expiratory mechanism and the effect of different breathing rates on nasal function have been presented. The value of maximum wall shear stress at the vestibule region increased by more than 2000 % as the flow rate increased from 7.5 to 40 L/min. The complicated anatomy of the nasal cavity has been naturally designed to attain the physiological function desired to facilitate normal breathing. The xix current study has identified certain gender based anatomical and physiological differences. The use of computational fluid dynamic has assisted in the understanding of these differences which could not be earlier quantified based on mere medical observation and measurement devices. The influence of postural changes in nasal cavity has also been investigated. Around 0.3% change in the average static pressure is observed while changing from sitting to supine position. The change in the direction of gravity due to change of posture significantly influences the flow parameters and hence should be considered in all future studies involving nasal flow. Most of the researchers employ plug flow boundary definitions to address the flow problems associated with nasal flow. This study has revealed the fallacy of such a definition and found significant differences in values obtained in either case. Comparative study of the pull flow model and the plug flow model has found significant variations highlighting the need for using the right boundary conditions. At the nasal valve, the resistance for plug flow was 0.311 Pa-min/L and for pull flow the value was 0.147 Pa-min/L. Maximum variation was noticed at the vestibule region with 0.3578 Pa-min/L. The average velocity for nasal vestibule and nasal valve is 1.4m/s and 1.6m/s for plug flow. Whereas, for pull flow case, the average velocity value in nasal vestibule and nasal valve region was observed to be around 0.96m/s and 1.41m/s respectively. A correct approach therefore to the numerical model is the pull flow model, which more directly represents the physiological inspiratory mechanism

Investigation of fontanelle photoplethysmographs and oxygen saturations in intensive care neonates and infants utilising miniature photometric sensors

In children and newborn babies on intensive care, information regarding blood oxygen saturation (SpO2) is determined non-invasively by a device called a pulse oximeter. Sensors are usually placed on a hand or foot where their operation relies on the presence of pulsatile arterial blood. Light shines at two or more wavelengths (usually red and infrared) into the tissue where the pulsatile blood modulates, absorbs and scatters the different wavelengths of light in varying amounts and is detected by a photo-detector as a photoplethysmograph (PPG). The spectral information received is then processed electronically and digitally to determine the amount of haemoglobin present. In the sickest of children blood supply can become compromised to these sensor locations and the pulsatile component of the blood may diminish and pulse oximeter readings may become unreliable, especially at times when accurate blood oxygen information would be vital. Currently the alternative is to take blood from an arterial line and run a relatively lengthy analysis (pulse oximeters are near-instantaneous in their operation) that may be unnecessary if the pulse oximeter could be relied upon at these critical moments. In the smallest of babies invasive sampling of blood becomes even more of an issue as any blood loss could lead to hypovolaemia and introduce extra sites of infection plus it causes a lot of stress to the neonate. Since central blood flow may be preferentially preserved, the anterior fontanelle was investigated as an alternative monitoring site. Custom reflectance fontanelle and reference PPG sensors have been designed and built to investigate the fontanelle in those children at risk of peripheral supply compromise. Dedicated instrumentation and software has also been successfully developed for the control of the sensor electronics and the data-logging of PPG signals for retrospective analysis. Sixteen neonates were recruited for fontanelle monitoring; all were ASA 1 – 3 (ASA ranges from 1 to 5 where 1 is the least sick and 5 is the most critically ill). As part of the approved protocol the delivered oxygen to the patients was artificially altered to look for corresponding changes in PPG signal amplitudes. Amplitude results reveal strong correlations (R > 0.5) between the reference sensor (placed on the foot) and the fontanelle sensor. This suggests that the fontanelle sensor is sensitive to changes in amplitude when oxygen in the blood alters. Correlation of the health of the child, using the ASA score, and the difference in amplitudes of PPGs between the sensors reveals that the fontanelle sensor does detect increasing fontanelle PPG amplitudes when compared to the PPGs from the reference sensor the sicker the child is, confirming that pulsatile flow is being preferentially preserved at the fontanelle in those children who are the most at risk from peripheral supply compromise. SpO2 estimation at the fontanelle reveals a mean difference of 2.2 % to the SpO2 as read by the commercial device and a 1.7 % difference to the blood gas results. These results confirm that the anterior fontanelle may be used as an alternative location for SpO2 measurement in those who are at most risk of peripheral supply compromise

Clinical evaluation of a new optical fibre method of measuring oxygen saturation using photoplethysmograph signals reflected from internal tissues

MD (Res)Traditional methods of measuring oxygen saturation, e.g. pulse oximetry, depend on an adequate peripheral circulation and have a 20–30 second lag time before readings are obtained. This was a series of evaluations of novel optical probes, designed to measure oxygen saturation using fibreoptic technology directly from internal organs including the brain, oesophagus and organs with splanchnic circulations. A series of pilot studies were proposed and research ethics approval obtained to carry out studies in humans, under general anaesthesia, using these probes. Innovative reflectance probes were designed specifically for each of the four applications, so as to obtain potentially useful signals needed for signal processing, analysis and evaluation. Signals were successfully obtained from the brain, oesophagus and splanchnic region in almost all of the patients recruited. Good quality photoplethysmograph signals were recorded and these were translated into clinically meaningful values of oxygen saturation comparable to traditional methods of pulse oximetry. Overall, the signals were prone to movement artefacts as well as occasional interference from surgical diathermy and other sources. Nonetheless, the probes could prove to be a useful alternative to conventional external transmittance pulse oximetry methods as well as providing useful information regarding regional perfusion and oxygenation. The success of these pilot studies will form the basis of more research in the area and further development of such probes on the medical engineering front