Changes in nasal airflow and heat transfer correlate with symptom improvement after surgery for nasal obstruction

Abstract

Surgeries to correct nasal airway obstruction (NAO) often have less than desirable outcomes, partly due to the absence of an objective tool to select the most appropriate surgical approach for each patient. Computational fluid dynamics (CFD) models can be used to investigate nasal airflow, but variables need to be identified that can detect surgical changes and correlate with patient symptoms. CFD models were constructed from pre- and post-surgery computed tomography scans for 10 NAO patients showing no evidence of nasal cycling. Steady-state inspiratory airflow, nasal resistance, wall shear stress, and heat flux were computed for the main nasal cavity from nostrils to posterior nasal septum both bilaterally and unilaterally. Paired t-tests indicated that all CFD variables were significantly changed by surgery when calculated on the most obstructed side, and that airflow, nasal resistance, and heat flux were significantly changed bilaterally as well. Moderate linear correlations with patient-reported symptoms were found for airflow, heat flux, unilateral allocation of airflow, and unilateral nasal resistance as a fraction of bilateral nasal resistance when calculated on the most obstructed nasal side, suggesting that these variables may be useful for evaluating the efficacy of nasal surgery objectively. Similarity in the strengths of these correlations suggests that patient-reported symptoms may represent a constellation of effects and that these variables should be tracked concurrently during future virtual surgery planning.

An Interactive, Patient-Specific Virtual Surgical Planning System for Upper Airway Obstruction Treatments

“…Ten patients from the Rhee study cohort were selected as described in [7], [8]. This cohort consists of patients recruited from the Ear, Nose, and Throat clinic at MCW who were at least 15 years old, had a clinical diagnosis of non-reversible, surgically treatable nasal obstruction (deviated septum, turbinate hypertrophy resistant to medical treatment, or lateral nasal wall collapse), elected to have surgery, and provided written, informed consent.…”

“…This method was successfully used for pediatric airways in VPAW and the trim parameters were modified to better fit the adult airways in this study. These segmentations were compared to the previous segmentations developed in Mimics (http://www.materialise.com/en/medical/software/mimics,) [7] and validated by subject matter experts.…”

“…To verify the implementation, one of the original Mimics segmentations was analyzed with a pressure drop across the nasal passages as the boundary condition. The results of the LBM analysis were compared to the Fluent simulations from previous work [7], [8]. …”

Mechanical Nasal Dilators for the Management of Nasal Obstruction

“…This value is very close to the reduction in nasal resistance after surgery found using preoperative and postoperative computed tomography scan-based CFD models in patients with nasal airway obstruction. 4 Although this cohort underwent surgical procedures that included but were not limited to butterfly or spreader grafts, further research to quantify the statement by Kiyohara and colleagues 1 that external nasal dilators emulate surgical procedures such as these grafts may be warranted. Kiyohara and colleagues 1 note that many of the devices they identified aim to provide temporary relief from nasal congestion and obstruction in normally healthy people.…”

“…Other studies have correlated mucosal cooling with symptoms in preoperative and postoperative patients treated for nasal airway obstruction as well. 4,8 It would be interesting to evaluate the ef- …”