Modelling the effects of post-FESS middle turbinate synechiae on sinonasal physiology: A computational fluid dynamics study.

OBJECTIVE(S): Chronic rhinosinusitis (CRS) is common and often requires surgical intervention. Surgical failure may lead to persistent symptoms and recalcitrant disease, often secondary to synechiae between the middle turbinate (MT) and lateral nasal wall. Synechiae prevention techniques have been extensively investigated, however evidence for the effect of synechiae on sinonasal physiology is lacking. We aimed to model the effects of MT synechiae on a post-functional endoscopic sinus surgery (FESS) sinonasal cavity using computational fluid dynamics (CFD). METHODS: DICOM data from a CT-sinus of a healthy 25-year-old female was segmented to create a three-dimensional model. Virtual surgery was performed to simulate a "full-house" FESS procedure. Multiple models were created, each with a single unilateral virtual MT synechia of varying extent. CFD analysis was performed on each model and compared with a post-FESS control model without synechiae. Airflow velocity, humidity and mucosal surface and air temperature values were calculated. RESULTS: All synechiae models demonstrated aberrant downstream sinonasal airflow. There was reduced ventilation of the ipsilateral frontal, ethmoid and sphenoid sinuses, with a concentrated central "jet" in the middle meatus region. Effects were proportionate to the size of synechiae. The impact on bulk inspired airflow was negligible. CONCLUSION: Post-FESS synechiae between the MT and lateral nasal wall significantly disrupt local downstream sinus ventilation and nasal airflow. These findings may explain the persistent symptoms seen in post-FESS CRS patients with MT synechiae, reinforcing the importance of prevention and adhesiolysis. Larger cohort studies with multiple models of actual post-FESS patients with synechiae are required to validate these findings.

The Impact of Adhesions on Nasal Airflow: A Quantitative Analysis Using Computational Fluid Dynamics.

BACKGROUND: Nasal adhesions (NAs) are a known complication of nasal airway surgery. Even minor NAs can lead to significant postoperative nasal airway obstruction (NAO). Division of such NAs often provides much greater relief than anticipated. OBJECTIVE: We examine the impact of NAs at various anatomical sites on nasal airflow and mucosal cooling using computational fluid dynamics (CFD) and multiple test subjects. METHODS: CT scans of healthy adult subjects were used to construct three-dimensional nasal airway computational models. A single virtual 2.5 mm diameter NA was placed at one of five sites commonly seen following NAO surgery within each nasal cavity bilaterally, resulting in 10 NA models and 1 NA-free control for each subject. CFD analysis was performed on each NA model and compared with the subject's NA-free control model. RESULTS: 4 subjects were recruited to create 44 computational models. The NAs caused the airflow streamlines to separate, leading to a statistically significant increase in mucosal temperature immediately downstream to the NAs (wake region). Changes in the mucosal temperature in the wake region of the NAs were most prominent in anteriorly located NAs with a mean increase of 1.62 °C for the anterior inferior turbinate NAs (P < .001) and 0.63 °C for the internal valve NAs (P < .001). CONCLUSION: NAs result in marked disruption to airflow patterns and reduced mucosal cooling on critical surfaces, particularly in the wake region. Reduced wake region mucosal cooling may be a contributing factor to the exaggerated perception of nasal obstruction experienced by patients with NAs.

Flow Patterns and Particle Residence Times in the Oral Cavity during Inhaled Drug Delivery.

Pulmonary drug delivery aims to deliver particles deep into the lungs, bypassing the mouth−throat airway geometry. However, micron particles under high flow rates are susceptible to inertial impaction on anatomical sites that serve as a defense system to filter and prevent foreign particles from entering the lungs. The aim of this study was to understand particle aerodynamics and its possible deposition in the mouth−throat airway that inhibits pulmonary drug delivery. In this study, we present an analysis of the aerodynamics of inhaled particles inside a patient-specific mouth−throat model generated from MRI scans. Computational Fluid Dynamics with a Discrete Phase Model for tracking particles was used to characterize the airflow patterns for a constant inhalation flow rate of 30 L/min. Monodisperse particles with diameters of 7 µm to 26 µm were introduced to the domain within a 3 cm-diameter sphere in front of the oral cavity. The main outcomes of this study showed that the time taken for particle deposition to occur was 0.5 s; a narrow stream of particles (medially and superiorly) were transported by the flow field; larger particles > 20 µm deposited onto the oropharnyx, while smaller particles < 12 µm were more disperse throughout the oral cavity and navigated the curved geometry and laryngeal jet to escape through the tracheal outlet. It was concluded that at a flow rate of 30 L/min the particle diameters depositing on the larynx and trachea in this specific patient model are likely to be in the range of 7 µm to 16 µm. Particles larger than 16 µm primarily deposited on the oropharynx.

Inhalation and deposition of spherical and pollen particles after middle turbinate resection in a human nasal cavity.

Middle turbinate resection significantly alters the anatomy and redistributes the inhaled air. The superior half of the main nasal cavity is opened up, increasing accessibility to the region. This is expected to increase inhalation dosimetry to the region during exposure to airborne particles. This study investigated the influence of middle turbinate resection on the deposition of inhaled pollutants that cover spherical and non-spherical particles (e.g. pollen). A computational model of the nasal cavity from CT scans, and its corresponding post-operative model with virtual surgery performed was created. Two constant flow rates of 5 L/min, and 15 L/min were simulated under a laminar flow field. Inhaled particles including pollen (non-spherical), and a spherical particle with reference density of 1000 kg/m3 were introduced in the surrounding atmosphere. The effect of surgery was most prominent in the less patent cavity side, since the change in anatomy was proportionally greater relative to the original airway space. The left cavity produced an increase in particle deposition at a flow rate of 15 L/min. The main particle deposition mechanisms were inertial impaction, and to a lesser degree gravitational sedimentation. The results are expected to provide insight into inhalation efficiency of different aerosol types, and the likelihood of deposition in different nasal cavity surfaces.

The impact of nasal adhesions on airflow and mucosal cooling - A computational fluid dynamics analysis.

Nasal adhesions are a known postoperative complication following surgical procedures for nasal airway obstruction (NAO); and are a common cause of surgical failure, with patients often reporting significant NAO, despite relatively minor adhesion size. Division of such nasal adhesions often provides much greater relief than anticipated, based on the minimal reduction in cross-sectional area associated with the adhesion. The available literature regarding nasal adhesions provides little evidence examining their quantitative and qualitative effects on nasal airflow using objective measures. This study examined the impact of nasal adhesions at various anatomical sites on nasal airflow and mucosal cooling using computational fluid dynamics (CFD). A high-resolution CT scan of the paranasal sinuses of a 25-year-old, healthy female patient was segmented to create a three-dimensional nasal airway model. Virtual nasal adhesions of 2.5 mm diameter were added to various locations within the nasal cavity, representing common sites seen following NAO surgery. A series of models with single adhesions were created. CFD analysis was performed on each model and compared with a baseline no-adhesion model, comparing airflow and heat and mass transfer. The nasal adhesions resulted in no significant change in bulk airflow patterns through the nasal cavity. However, significant changes were observed in local airflow and mucosal cooling around and immediately downstream to the nasal adhesions. These were most evident with anterior nasal adhesions at the internal valve and anterior inferior turbinate. Postoperative nasal adhesions create local airflow disruption, resulting in reduced local mucosal cooling on critical surfaces, explaining the exaggerated perception of nasal obstruction. In particular, anteriorly located adhesions created greater disruption to local airflow and mucosal cooling, explaining their associated greater subjective sensation of obstruction.

Moderators of angiogenesis in muscle flaps: A non-randomised animal study.

INTRODUCTION: A muscle flap can survive a pedicle injury under favourable conditions. In the reconstruction of compound limb injuries, the wound milieu is variable and may affect the rate and manner of neovascularisation. Our aim is to determine the effect of some key clinical variables on neovascularisation in muscle flaps in an animal model. METHODOLOGY: The pectoralis profundus was raised in 60 rats and covered with a skin graft. Fifteen rats were allocated to each of the following groups: separation of the flap from the skin inset (S), inflammation by inoculation with Staphylococcus aureus (I), flap elevation with harmonic scalpel (H) and preservation of the motor nerve (N) as well as compared to controls (C). Graft take and wound complications were assessed five days later, as well as perfusion before and after pedicle ligation, by laser Doppler flowmetry and neovascularisation using barium angiography. RESULTS: Flaps with an intact motor nerve had significantly higher graft take than controls (59% vs 29%). Perfusion change was lesser in all study groups than in controls, although the extent of flap necrosis was not significantly different. Only flaps raised with the harmonic scalpel generated more new vessels than controls at the inset (9.6 vs 3.2), particularly at the origin of the muscle (1.10 vs 0.19). CONCLUSIONS: All study groups were less dependent on their pedicle for perfusion than controls. The use of the harmonic scalpel and increased inflammation seem pro-angiogenic, although they do not reduce flap necrosis after simulated pedicle injury. Neovascularisation will preferentially bridge to the skin at the inset rather than tissues in the base of the wound. It is likely that flap necrosis is the result of a combination of unfavourable variables rather than one in isolation.

Gallbladder torsion: a diagnostic challenge.

80-year-old female presented with clinical findings suggestive of acute cholecystitis. Intraoperatively we discovered a dusky gallbladder with gangrenous patches and gallbladder torsion with 270 degrees clockwise rotation along the longitudinal axis. Gallbladder torsion is a rare cause of acute cholecystitis with less than 500 cases published in the literature. Gallbladder torsion should be included in the list of differential diagnoses in patients suspected of having acute cholecystitis especially when there are inconsistencies between clinical features and imaging. It is worth noting that 3-dimensional reconstructed CT may be useful in preoperative diagnosis of gallbladder torsion.