Computational fluid dynamic analysis of aggressive turbinate reductions: is it a culprit of empty nose syndrome?

Abstract

Background: Empty nose syndrome (ENS) remains highly controversial, with aggressive inferior turbinate reduction (ITR) or mucociliary dysfunction frequently implicated. However, the appropriate degree of ITR is highly debatable. Methods:We applied individual computed tomography (CT)-based computational fluid dynamics (CFD) to 5 patients receiving relatively aggressive ITR but with no ENS symptoms, and compared them to 27 symptomatic ENS patients who all had histories of aggressive ITRs, and 42 healthy controls. Patients' surgical outcomes were confirmed with 22-item Sino-Nasal Outcome Test (SNOT-22) (ITR: 6.40 ± 4.56; ENS: 58.2 ± 15.9; healthy: 13.2 ± 14.9), Nasal Obstruction Symptom Evaluation (NOSE) scores (ITR: 4.00 ± 2.24; ENS: 69.4 ± 17.1; healthy: 11.9 ± 12.9), and Empty Nose Syndrome 6-Item Questionnaire (ENS6Q) (ࣙ11 for ENS). Results:Both aggressive ITR without ENS symptoms and symptomatic ENS patients had significantly lower nasal resistance (ITR: 0.059 ± 0.020 Pa·s/mL; ENS: 0.052 ± 0.015 Pa·s/mL; healthy: 0.070 ± 0.021 Pa·s/mL) and higher crosssectional areas surrounding the inferior turbinate (ITR: 0.94 ± 0.21 cm 2 ; ENS: 1.19 ± 1.05 cm 2 ; healthy: 0.42 ± 0.22 cm 2 ) than healthy controls. The lack of significant differences among patient groups indicated similar degrees of surgeries between ITR with and without ENS symptom cohorts. However, symptomatic ENS patients have paradoxical significantly less airflow in the inferior meatus (ITR: 47.7% ± 23.6%; ENS: 25.8% ± 17.6%; healthy: 36.5 ± 15.9%; both p < 0.01), but higher airflow around the middle meatus (ITR: 49.7% ± 22.6%; ENS: 66.5% ± 18.3%; healthy: 49.9% ± 15.1%, p < 0.0001) than aggressive ITR without symptoms and controls. Aggressive ITR patients have increased inferior meatus airflow as expected (p < 0.05). This imbalanced airflow produced less inferior wall-shear-stress distribution among symptomatic ENS patients only (ITR: 42.45% ± 11.4%; ENS: 32.2% ± 12.6%; healthy: 49.7% ± 9.9%). ENS patients (n = 12) also had impaired nasal trigeminal function, as measured by menthol lateralization detection thresholds (ITR: 15.2 ± 1.2; ENS: 10.3 ± 3.9; healthy: 13.8 ± 3.09, both p < 0.0001). Surprisingly, aggressive ITR patients without ENS symptoms have be er menthol lateralization detection thresholds (LDTs) than healthy controls. Conclusion:Although turbinate tissue loss is linked with ENS, the degree of ITR that might distinguish postoperative patient satisfaction in their nasal breathing vs development of ENS symptoms is unclear. Our results suggest that a combination of distorted nasal aerodynamics and loss of mucosal sensory function may potentially lead to ENS symptomology. C 2019 ARS-AAOA, LLC.

The cotton test redistributes nasal airflow in patients with empty nose syndrome

“…This suggests that the relationship between airflow distribution, regional airflow rate, and regional resistance may be exceedingly complex, and are important factors to consider when designing, implementing, or selecting implants for patients with ENS symptoms. This distribution of airflow in the presence of cotton placement is comparable with previous CFD results from healthy controls, and cotton parameters, such as volume and position, should be further explored to characterize its impact on optimizing the distribution of nasal airflow.…”

“…Figure B and C represents cross‐sectional slices taken at about 60% of the length of the nasal passage, just posterior to the cotton plug pre‐ and post‐cotton insertion. Figure B shows that the effects of cotton placement and initial increase of airflow velocity actually bring the nasal airflow into a more balanced flow distribution, similar to what is seen in healthy controls . Overall flow rate decreases with cotton insertion, however patients are reporting improved airflow.…”

“…Given these observations and indications, our goal was to further understand the physiologic mechanisms that explain the changes in upper airway breathing after placement of a cotton plug in symptomatic ENS patients. We hypothesized that insertion of a cotton plug would alter nasal airflow from the characteristic ENS flow patterns to a more dispersed, normal pattern.…”

Inferior meatus augmentation procedure (IMAP) normalizes nasal airflow patterns in empty nose syndrome patients via computational fluid dynamics (CFD) modeling

“…13 Thus, the goal of this study was to use a similar approach to characterize changes in the profile of nasal airflow in ENS patients 6 months after IMAP surgery so that we may further understand the physiologic mechanisms driving the symptomatic improvement with tissue replacement surgery. We hypothesized that the restoration of inferior turbinate tissue bulk via IMAP would alter the characteristic ENS airflow pattern to the middle meatus, 11,12 and result in increased perception of airflow.…”

Answers to some common rhinologic questions

“…The study using a computational fluid dynamic analysis of empty nose syndrome patients by Malik et al . had thought‐provoking results.…”