Insights from 3D modeling and fluid dynamics in COVID-19 pneumonia.

We address the lack of research regarding aerodynamic events behind respiratory distress at COVID-19. The use of chest CT enables quantification of pneumonia extent; however, there is a paucity of data regarding the impact of airflow changes. We reviewed 31 COVID-19 patients who were admitted in March 2020 with varying severity of pulmonary disease. Lung volumes were segmented and measured on CT images and patient-specific models of the lungs were created. Incompressible, laminar, and three-dimensional Navier-Stokes equations were used for the fluid dynamics (CFD) analyses of ten patients (five mild, five pneumonia). Of 31 patients, 17 were female, 18 had pneumonia, and 2 were deceased. Effective lung volume decreased in the general group, but the involvement of the right lung was prominent in dyspnea patients. CFD analyses revealed that the mass flow distribution was significantly distorted in pneumonia cases with diminished flow rate towards the right lung. In addition, the distribution of flow parameters showed mild group had less airway resistance with higher velocity (1.228 m/s vs 1.572 m/s) and higher static pressure values at airway branches (1.5112 Pa vs 1.3024 Pa). Therefore, we conclude that airway resistance and mass flow rate distribution are as important as the radiological involvement degree in defining the disease severity.

Effect of glottic geometry on breathing: three-dimensional unsteady numerical simulation of respiration in a case with congenital glottic web.

Glottic obstruction is a major cause of dyspnea. Without understanding the normal function of the glottis in breathing, treating dyspnea does not restore normal physiology. Therefore, we designed a computational fluid dynamics (CFD) model that tested the respiratory cycle in larynges with normal glottis and congenital glottic web (CGW). A CGW case and a control subject (CC) were selected from the computed tomography (CT) archive. 3D computational models of the larynges with structured boundary layer were constructed from axial CT images after mesh refinement study. CFD analyses were based on the Reynolds-averaged Navier-Stokes approach. Incompressible flow solver (pressure-based) and SST k-w turbulence model were chosen for this study. To simulate a real-time breathing process, time varying flow rate boundary condition was derived from the spirometer of a healthy, non-smoking woman. Glottic areas were measured as 51.64 and 125.43 mm(2) for the CGW patient and CC, respectively. Time-dependent velocity contours and streamlines for the CC and CGW patient were drawn. The CC showed uniform flow, all through the inspiration and expiration phases. However, the CGW patient showed separation of flow at the glottis level, which caused areas of stagnation in the supraglottis (during expiration) and the subglottis and trachea (during inspiration). Specialized geometry of the normal larynx maintained uniform flow with low shear stress values on the wall even at high mass flow rates. Distortion of this geometry may cause obstruction of flow at multiple levels and, therefore, should be evaluated at multiple levels.

A computational study on the characteristics of airflow in bilateral abductor vocal fold immobility.

OBJECTIVES/HYPOTHESIS: To evaluate airway sufficiency and airflow dynamics in a group of patients who underwent a posterior transverse laser cordotomy (PTLC) procedure. STUDY DESIGN: Mixed methods research, university hospital setting. METHODS: Sixteen patients who underwent a PTLC procedure volunteered to be involved in this study. Dyspnea levels, voice, and glottic opening in indirect laryngoscopy were evaluated subjectively. The airway was evaluated objectively by pulmonary function tests, and glottic areas were measured from axial computed tomography (CT) images. The control group consisted of 63 subjects from the tomography archive. For computational fluid dynamics (CFD) analyses, two subjects from the study group were chosen on the basis of obstruction level, and a normal female subject was selected from the control group. Cartesian coordinates for airway boundaries were determined from axial CT images, and a three-dimensional computational model of the larynx was constructed. Flow simulations were performed with two different flow conditions during inspiration. Comparison of velocity, static pressure, turbulence intensity, and wall shear stress distribution values were made between selected cases and control. RESULTS: Pulmonary data varied widely and did not correlate with the size of the glottic area or dyspnea level. CFD analyses revealed that in addition to obstruction at the glottic level, aerodynamic properties of the larynx are altered due to loss in muscular tonus. Also, the contour of the glottic opening was found to be very important in determining the character of airflow as laminar or turbulent. CONCLUSIONS: Patients have considerable differences in their flow patterns and force distributions during respiration. Patient-specific models may help in evaluation and treatment planning.

Four hands technique in transoral endoscope-assisted fixation of condyle fractures.

OBJECTIVE: We present the short-term treatment results of a modified technique in transoral endoscopic condyle repair. DESIGN: A pilot prospective study from April 2006 to November 2007. SETTING: Ankara University Medical School Teaching Hospital. METHODS: Four patients with subcondylar fracture were treated with transoral endoscopic condyle repair. Preliminary restoration of the occlusion was provided with maxillomandibular fixation. Four hands endoscopic sinus surgery principles were adapted to transoral endoscopic condyle repair. MAIN OUTCOME MEASURES: Providing condylar stabilization with good occlusion and temporomandibular joint function was expected from treatment. RESULTS: Open reduction and internal fixation were achieved in all patients. Condylar stabilization was confirmed by intraoperative endoscopic findings and postoperative panoramic radiographs. Uneventful healing with good occlusion and temporomandibular joint function were noted in 3 to 14 months of follow-up. CONCLUSION: Endoscope-assisted minimal invasive procedures have been taking more part in head and neck soft tissue and trauma surgery. The cost of instruments and technical difficulties are the main constraints of endoscopic techniques. In this study, we present a practical way to perform transoral endoscopic condyle repair using the otolaryngologist's standard sinus surgery endovisual equipment and a titanium miniplate system. With the addition of a surgical hand, successful treatment results could be achieved with reduced cost.

The clinical value of pharyngeal pH monitoring using a double-probe, triple-sensor catheter in patients with laryngopharyngeal reflux.

OBJECTIVE: To determine the clinical value of pharyngeal pH monitoring for the diagnosis of laryngopharyngeal reflux (LPR) by using a double-probe, triple-sensor catheter in patients with symptoms of LPR. DESIGN: Prospective review of pH values recorded at the pharyngeal sensor, with the sensor placed in the proximal esophagus in patients with suspected LPR. SETTING: Tertiary care university hospital. PATIENTS: Thirty-three consecutive patients with symptoms of LPR. MAIN OUTCOME MEASURES: A pH test result was considered abnormal if a single reflux episode was detected in the hypopharynx and if, in the proximal esophagus, the total percentage of time the pH value was below 4 was 1.0% or higher. Data obtained from sensors were compared to determine the validity of pharyngeal sensor. Correlation between patients' reflux finding scores, reflux finding indexes, and reflux episodes were analyzed. RESULTS: Of 33 patients, 17 had more than 1 reflux episode detected by the pharyngeal sensor and 19 had pathological reflux detected by the proximal esophageal sensor. Four patients who had pharyngeal reflux had a normal esophageal acid exposure time, and 6 patients who had pathological reflux detected by the proximal esophageal sensor did not experienced any pharyngeal reflux episode. Four patients would have had a false-negative test result and 6 subjects would have had a false-positive test result if a hypopharyngeal pH sensor was not implemented. CONCLUSIONS: The adjustable, bifurcated, triple-sensor pH probe allows identifying true hypopharyngeal reflux episodes. If single-probe, double-sensor pH monitoring is to be performed, the proximal probe should be placed in the pharynx, not in the upper esophagus.

Aerodynamic, acoustic and functional results of posterior transverse laser cordotomy for bilateral abductor vocal fold paralysis.

Bilateral abductor vocal fold paralysis (BAVFP) is a rare but life-threatening condition which may require an emergency tracheotomy procedure. The ideal surgical technique for this condition should improve quality of life by relieving the airway obstruction while preserving laryngeal functions such as phonation and deglutition. Posterior transverse laser cordotomy (PTLC) was first described by Dennis and Kashima as a technique for providing an airway at the posterior glottis without pre-operative tracheotomy; they reported it as a successful method with satisfactory functional results. The aim of this prospective study was to evaluate long term acoustic, aerodynamic and functional results of the primary bilateral PTLC technique in 22 BAVFP patients. Severity of dyspnoea was evaluated using a five-level subjective symptom scale graded according to the limitation in daily activity and level of respiratory difficulty. Aerodynamic and acoustic analyses were performed pre-operatively and prospective changes in aerodynamic and acoustic parameters were collected after one post-operative year.

Unilateral hearing loss as a presenting manifestation of granulocytic sarcoma (chloroma).

OBJECTIVE: To present a case of acute granulocytic sarcoma of the cerebellopontine angle whose presenting symptom was sudden onset unilateral sensorineural hearing loss. STUDY DESIGN: Case report and review of the literature (MEDLINE, 1962-2005). METHODS: A 34-year-old female patient with acute myeloid leukemia on remission admitted because of sudden hearing loss in her right ear for 10 days. She had experienced occasional tinnitus, ear fullness, and dizziness for a couple of months. After confirmation of her audiometric findings with auditory brainstem responses, the patient was put on a treatment regimen for sudden hearing loss. RESULTS: On the second day of treatment, she developed ipsilateral facial paralysis, hoarseness caused by ipsilateral vocal fold paralysis, and nystagmus. Magnetic resonance imaging of the cranium revealed findings consistent with granulocytic sarcoma at the cerebellopontine angle, infiltrating the internal acoustic canal. As increased intracranial pressure symptoms developed subsequently, subtotal tumor resection was performed. However, the patient was lost, with Cushing's triad at the second postoperative month during postoperative chemotherapy. CONCLUSION: Although up to 40% of leukemic patients may have otologic symptoms, sudden onset of sensorineural hearing loss is very rare. The patient presented in this report is the first reported case with a granulocytic sarcoma of the cerebellopontine angle who presented with acute sensorineural hearing loss. Despite the rarity of such a case, we would like to emphasize that leukemia must be kept in mind as an etiologic factor in sensorineural hearing loss and suggest that complete blood count and temporal bone imaging be routinely obtained.