Computational Fluid Dynamics and Its Potential Applications for the ENT Clinician

This article is an examination of computational fluid dynamics in the field of otolaryngology, specifically rhinology. The historical development and subsequent application of computational fluid dynamics continues to enhance our understanding of various sinonasal conditions and surgical planning in the field today. This article aims to provide a description of computational fluid dynamics, the methods for its application, and the clinical relevance of its results. Consideration of recent research and data in computational fluid dynamics demonstrates its use in nonhistological disease pathology exploration, accompanied by a large potential for surgical guidance applications. Additionally, this article defines in lay terms the variables analyzed in the computational fluid dynamic process, including velocity, wall shear stress, area, resistance, and heat flux.

How Does Oxymetazoline Change Nasal Aerodynamics and Symptomatology in Patients with Turbinate Hypertrophy?

OBJECTIVES

Oxymetazoline relieves nasal obstructive symptoms via vasoconstriction, however, the changes in nasal structures and aerodynamics that impact symptoms the most remain unclear.

METHODS

This prospective, longitudinal, and single blinded cohort study applied Computational Fluid Dynamic (CFD) modeling based on CT scans at baseline and post-oxymetazoline on 13 consecutive patients with chronic nasal obstruction secondary to inferior turbinate hypertrophy from a tertiary medical center. To account for placebo effect, a sham saline spray was administered with subject blindfolded prior to oxymetazoline, with 30 min rest in between. Nasal Obstruction Symptom Evaluation (NOSE) and unilateral Visual Analogue Scale (VAS) scores of nasal obstructions were collected at baseline, after sham, and 30 min after oxymetazoline.

RESULTS

Both VAS and NOSE scores significantly improved from baseline to post-oxymetazoline (NOSE: 62.3 ± 12.4 to 31.5 ± 22.5, p < 0.01; VAS: 5.27 ± 2.63 to 3.85 ± 2.59, p < 0.05), but not significantly from baseline to post-sham. The anatomical effects of oxymetazoline were observed broadly throughout the entire length of the inferior and middle turbinates (p < 0.05). Among many variables that changed significantly post-oxymetazoline, only decreased nasal resistance (spearman r = 0.4, p < 0.05), increased regional flow rates (r = -0.3 to -0.5, p < 0.05) and mucosal cooling heat flux (r = -0.42, p < 0.01) in the inferior but not middle turbinate regions, and nasal valve Wall Shear Stress (WSS r = -0.43, p < 0.05) strongly correlated with symptom improvement.

CONCLUSION

Oxymetazoline broadly affects the inferior and middle turbinates, however, symptomatic improvement appears to be driven more by global nasal resistance and regional increases in airflow rate, mucosal cooling, and WSS, especially near the head of the inferior turbinate.

LEVEL OF EVIDENCE

3: Well-designed, prospective, single blinded cohort trial. Laryngoscope, 134:1100-1106, 2024.

3D Printing as a Planning Tool to Optimize Sinonasal Irrigation

BACKGROUND

Topical sinus irrigation plays a critical role in the management of sinonasal diseases. Yet, the penetration of irrigant to targeted sinuses may be highly variable and difficult to predict. Here, we investigate the use of 3D printing as a planning tool to optimize outcomes.

METHODS

Eight post-operative models were 3D printed with a FormLabs Form3 printer based on individual CT scans. Irrigations were performed and video recorded with a squeeze bottle attached via silicon water-tight seal, in 4 head positions: 45° to-the-side, 90° to-the-side, 45° forward and 45° to-the-side, and 90° forward, with irrigation fluid entering the upper (conventional) or lower (backfill) nostrils.

RESULTS

Significant individual variations were observed in sinus penetration as a function of head position. In general, the maxillary sinus was the easiest to irrigate in most head positions (P < .05), followed by frontal and ethmoid, with sphenoid being the most difficult. Both the 90°-to-the-side and the 90°-forward positions were significantly more effective than the others (P < .05), with 90°-forward better for frontal sinuses and 90°-to-the-side superior for all other sinuses. The backfill was significantly superior to conventional technique in head positions involving a side tilt (P < .05).

CONCLUSION

Variations in technique and position significantly impacted irrigation outcome. Backfill irrigation that pushes fluid against gravity to pool around the ostium, seems to provide overall better outcomes. This study demonstrates the advantage of 3D printing as a rapid planning tool to guide irrigation strategies.

Otolaryngologists' radiological assessment of nasal septum deviation symptomatology

OBJECTIVES

Nasal Septal Deviation (NSD) is one of the most common causes of nasal obstruction. This study aims to further examine the clinical utility of imaging assessment in the workup and management of symptomatic nasal septal deviation, across all levels of medical training.

STUDY DESIGN

Cross-sectional survey.

METHODS

CT scans of 10 confirmed NSD patients and 36 healthy controls (HC) were mixed and emailed through anonymous REDCap surveys to otolaryngologists in the US. The HC had no reported sinonasal obstruction symptoms-NOSE (NSD: 62.2 ± 12.5; HC: 5.69 ± 5.99, p < 0.05); SNOT-22 (NSD: 31.4 ± 14.5; HC: 9.72 ± 10.76, p < 0.05). The images consisted of a coronal slice at each subject's most deviated location. Participants were instructed to choose the patients suspected to present with symptoms of sinonasal obstruction.

RESULTS

88 otolaryngologists responded to the survey. 18 were excluded due to incomplete responses. On average, they identified 64.2 ± 29.8% of symptomatic NSD subjects correctly, but misidentified 54.6 ± 34.6% of HC as symptomatic. Their decisions were strongly correlated to degree of NSD (r = 0.69, p < 0.05). There exists a significant degree of NSD among HC (38.7 ± 17.2%), which does not significantly differ from symptomatic subjects (51.0 + 18.7%, p = 0.09). Residents and fellows performed similarly, with responses correlated between levels of training (r = 0.84-0.96, p < 0.05).

CONCLUSIONS

The incorporation of a substantial number of otolaryngologists, large patient sample, and blind mixing with HC gives us greater insight to the relative contribution of the extent of septal deviation to symptoms of nasal obstruction. Although NSD is a common factor contributing to nasal obstruction, the results of this study suggest that it is difficult to reliably infer obstructive symptoms based on degree of NSD on CT.

LEVEL OF EVIDENCE

Three.