Quantification of airflow into the maxillary sinuses before and after functional endoscopic sinus surgery

Abstract

Background: The effects of increases in maxillary sinus (MS) airflow following functional endoscopic sinus surgery (FESS) are unknown. The goal of this study was to quantify the effects of FESS on airflow into the MS in a cohort of patients with chronic rhinosinusitis, and compare MS flow rate with patient-reported outcome measures.

Methods: A pilot study was conducted in which preoperative and postoperative computed tomography scans of 4 patients undergoing bilateral or unilateral FESS were used to create 3-dimensional (3D) reconstructions of the nasal airway and paranasal sinuses using Mimics™ (Materialise, Inc.). The size of the maxillary antrostomies post-FESS ranged from 107 to 160 mm(2). Computational meshes were generated from the 3D reconstructions, and steady-state, laminar, inspiratory airflow was simulated in each mesh using the computational fluid dynamics (CFD) software Fluent™ (ANSYS, Inc.) under physiologic, pressure-driven conditions. Airflow into the MS was estimated from the simulations and was compared preoperatively and postoperatively. In addition, patients completed preoperative and postoperative Rhinosinusitis Outcome Measure-31 (RSOM-31) questionnaires and scores were compared with MS airflow rates.

Results: CFD simulations predicted that average airflow rate into post-FESS MS increased by 18.5 mL/second, and that average flow velocity into the MS more than quadrupled. Simulation results also showed that MS flow rate trended with total RSOM-31 and all domain scores.

Conclusion: CFD simulations showed that the healed maxillary antrostomy after FESS can greatly enhance airflow into the MS. Our pilot study suggests that to some extent, increasing airflow into the MS may potentially improve chronic rhinosinusitis patients' quality of life pre-FESS and post-FESS.

Keywords: FESS; chronic rhinosinusitis; computational fluid dynamics; maxillary sinus; nasal airflow.

FIGURE 1

Coronal views from pre-FESS and post-FESS CT scans of all patients. CT = computed tomography; FESS = functional endoscopic sinus surgery.

FIGURE 2

Changes (post-FESS minus pre-FESS) in maxillary ostium surface area and flow rate into the maxillary sinus before and after FESS. FESS = functional endoscopic sinus surgery.

FIGURE 3

Airflow streamlines on the surgically altered side pre-FESS and post-FESS for select patients. Color indicates airflow velocity magnitude. FESS = functional endoscopic sinus surgery.

FIGURE 4

PRE minus POST differences in RSOM-31 survey for all subjects. A positive difference indicates improvement in symptom domain after surgery. POST = post-FESS; PRE = pre-FESS; RSOM-31 = Rhinosinusitis Outcome Measure-31.

FIGURE 5

Comparison of patients’ reported QOL survey and flow rate into the maxillary sinus. (A) Total RSOM-31 scores plotted against maxillary sinus inflow rate. (B) Nasal symptoms domain scores plotted against maxillary sinus inflow rate. (C) Eye symptoms domain scores plotted against maxillary sinus inflow rate. (D) Sleep symptoms domain scores plotted against maxillary sinus inflow rate. (E) Ear symptoms domain scores plotted against maxillary sinus inflow rate. (F) General symptoms domain scores plotted against maxillary sinus inflow rate. (G) Practical problems domain scores plotted against maxillary sinus inflow rate. (H) Emotional consequences domain scores plotted against maxillary sinus inflow rate. QOL = quality of life; RSOM-31 = Rhinosinusitis Outcome Measure-31.