Effects of Mucosal Decongestion on Nasal Aerodynamics: A Pilot Study.

OBJECTIVE: Mucosal decongestion with nasal sprays is a common treatment for nasal airway obstruction. However, the impact of mucosal decongestion on nasal aerodynamics and the physiological mechanism of nasal airflow sensation are incompletely understood. The objective of this study is to compare nasal airflow patterns in nasal airway obstruction (NAO) patients with and without mucosal decongestion and nondecongested healthy subjects. STUDY DESIGN: Cross-sectional study of a convenience sample. SETTING: Academic tertiary medical center. METHODS: Forty-five subjects were studied (15 nondecongested healthy subjects, 15 nondecongested NAO patients, and 15 decongested NAO patients). Three-dimensional models of the nasal anatomy were created from computed tomography scans. Steady-state simulations of airflow and heat transfer were conducted at 15 L/min inhalation rate using computational fluid dynamics. RESULTS: In the narrow side of the nose, unilateral nasal resistance was similar in decongested NAO patients and nondecongested healthy subjects, but substantially higher in nondecongested NAO patients. The vertical airflow distribution within the nasal cavity (inferior vs middle vs superior) was also similar in decongested NAO patients and nondecongested healthy subjects, but nondecongested NAO patients had substantially less middle airflow. Mucosal cooling, quantified by the surface area where heat flux exceeds 50 W/m2, was significantly higher in decongested NAO patients than in nondecongested NAO patients. CONCLUSION: This pilot study suggests that mucosal decongestion improves objective measures of nasal airflow, which is consistent with improved subjective sensation of nasal patency after decongestion.

Intranasal Insulin for the Treatment of Persistent Post-COVID-19 Olfactory Dysfunction.

OBJECTIVE: To investigate if intranasal insulin could be a treatment option for those suffering from recalcitrant olfactory dysfunction due to COVID-19. STUDY DESIGN: Prospective interventional cohort with a single group. SETTING: Sixteen volunteers with anosmia, severe hyposmia, or moderate hyposmia for more than 60 days as sequelae of severe acute respiratory syndrome coronavirus 2 infections were selected for the study. All volunteers reported that standard therapies, such as corticosteroids, have failed to improve their olfactory function. METHODS: Olfactory function was assessed by the Chemosensory Clinical Research Center test of olfaction (COT) before and after the intervention. Changes in qualitative, quantitative, and global COT scores were investigated. The insulin therapy session consisted of placing into each olfactory cleft 2 pieces of gelatin sponge soaked with neutral protamine Hagedorn (NPH) insulin, 40 IU on each side. The procedure was repeated twice a week for 1 month. Glycaemic blood level was measured before and after each session. RESULTS: The qualitative COT score rose 1.53 points, p = .0001, 95% confidence interval (CI) (-2.12 to -0.94). The quantitative COT score increased by 2.00 points, p = .0002, 95% CI (-3.59 to -1.41). Global COT score had an improvement of 2.01 points, p = .00003, 95% CI (-2.7 to -1.3). Glycaemic blood level dropped on average 10.4 mg/dL, p < .00003, 95% CI (8.1-12.8). CONCLUSION: Our results suggest that the administration of NPH insulin into the olfactory cleft yields a rapid improvement in the sense of smell of patients suffering from persistent post-COVID-19 olfactory dysfunction. Moreover, the procedure seems to be safe and tolerable.

Rhinomanometry Versus Computational Fluid Dynamics: Correlated, but Different Techniques.

BACKGROUND: Past studies reported a low correlation between rhinomanometry and computational fluid dynamics (CFD), but the source of the discrepancy was unclear. Low correlation or lack of correlation has also been reported between subjective and objective measures of nasal patency. OBJECTIVE: This study investigates (1) the correlation and agreement between nasal resistance derived from CFD (RCFD) and rhinomanometry (RRMN), and (2) the correlation between objective and subjective measures of nasal patency. METHODS: Twenty-five patients with nasal obstruction underwent anterior rhinomanometry before and after mucosal decongestion with oxymetazoline. Subjective nasal patency was assessed with a 0-10 visual analog scale (VAS). CFD simulations were performed based on computed tomography scans obtained after mucosal decongestion. To validate the CFD methods, nasal resistance was measured in vitro (REXPERIMENT) by performing pressure-flow experiments in anatomically accurate plastic nasal replicas from 6 individuals. RESULTS: Mucosal decongestion was associated with a reduction in bilateral nasal resistance (0.34 ± 0.23 Pa.s/ml to 0.19 ± 0.24 Pa.s/ml, p = 0.003) and improved sensation of nasal airflow (bilateral VAS decreased from 5.2 ± 1.9 to 2.6 ± 1.9, p < 0.001). A statistically significant correlation was found between VAS in the most obstructed cavity and unilateral airflow before and after mucosal decongestion (r = -0.42, p = 0.003). Excellent correlation was found between RCFD and REXPERIMENT (r = 0.96, p < 0.001) with good agreement between the numerical and in vitro values (RCFD/REXPERIMENT = 0.93 ± 0.08). A weak correlation was found between RCFD and RRMN (r = 0.41, p = 0.003) with CFD underpredicting nasal resistance derived from rhinomanometry (RCFD/RRMN = 0.65 ± 0.63). A stronger correlation was found when unilateral airflow at a pressure drop of 75 Pa was used to compare CFD with rhinomanometry (r = 0.76, p < 0.001). CONCLUSION: CFD and rhinomanometry are moderately correlated, but CFD underpredicts nasal resistance measured in vivo due in part to the assumption of rigid nasal walls. Our results confirm previous reports that subjective nasal patency correlates better with unilateral than with bilateral measurements and in the context of an intervention.

Sensitivity of nasal airflow variables computed via computational fluid dynamics to the computed tomography segmentation threshold.

Computational fluid dynamics (CFD) allows quantitative assessment of transport phenomena in the human nasal cavity, including heat exchange, moisture transport, odorant uptake in the olfactory cleft, and regional delivery of pharmaceutical aerosols. The first step when applying CFD to investigate nasal airflow is to create a 3-dimensional reconstruction of the nasal anatomy from computed tomography (CT) scans or magnetic resonance images (MRI). However, a method to identify the exact location of the air-tissue boundary from CT scans or MRI is currently lacking. This introduces some uncertainty in the nasal cavity geometry. The radiodensity threshold for segmentation of the nasal airways has received little attention in the CFD literature. The goal of this study is to quantify how uncertainty in the segmentation threshold impacts CFD simulations of transport phenomena in the human nasal cavity. Three patients with nasal airway obstruction were included in the analysis. Pre-surgery CT scans were obtained after mucosal decongestion with oxymetazoline. For each patient, the nasal anatomy was reconstructed using three different thresholds in Hounsfield units (-800HU, -550HU, and -300HU). Our results demonstrate that some CFD variables (pressure drop, flowrate, airflow resistance) and anatomic variables (airspace cross-sectional area and volume) are strongly dependent on the segmentation threshold, while other CFD variables (intranasal flow distribution, surface area) are less sensitive to the segmentation threshold. These findings suggest that identification of an optimal threshold for segmentation of the nasal airway from CT scans will be important for good agreement between in vivo measurements and patient-specific CFD simulations of transport phenomena in the nasal cavity, particularly for processes sensitive to the transnasal pressure drop. We recommend that future CFD studies should always report the segmentation threshold used to reconstruct the nasal anatomy.