3D Printing to Improve Nasal Irrigation Outcome

Chronic rhinosinusitis (CRS) is one of the most common medical conditions in the US, affecting an estimated 13% of adults, or some 30 million people. It accounts for 12.5 million physician office visits each year and an annual health care expenditure of $5.8 billion (National Health Interview Survey 2009, CDC). Major symptoms include nasal obstruction, facial pain/pressure, nasal discharge, purulence in the nasal cavity, and loss of smell. These symptoms significantly impact patient quality of life, even compared to chronic debilitating diseases such as diabetes and congestive heart failure.

Topical therapies play an integral role in the management of CRS, and high-volume irrigation delivery (e.g., neti pot, squeeze bottles) is more effective for achieving distribution to the sinuses than other topical delivery methods such as nasal sprays, nebulizers, or atomizers. Saline irrigations have been recommended in a number of clinical scenarios, including initial management of CRS and postoperative care. High-volume irrigations have also shown benefits for medication delivery, such as with mupirocin and corticosteroids. However, due to the intricate and variable anatomy of the human nasal airway, the efficacy of topical irrigations is inconsistent and difficult to predict. Previous studies from our group and others have shown that nasal irrigant may not reliably penetrate all sinuses, and the effectiveness varies depending on specific sinuses, head positions, injection angle, pressure, flow rates, and other factors. We currently do not have a clear understanding of the optimal delivery technique(s). In efforts to improve these outcomes, the efficacy of topical irrigation delivery to target sinuses is an area of active research. Yet, investigations have been limited by labor-intensive methodologies, such as cadaver studies or using colored dyes followed by endoscopy to visualize where the irrigation might have reached. Other studies have used irrigations with iodinated contrast followed by computed tomography (CT) scans to determine which sinuses collect contrast material. Similarly, technetium 99m sulfur colloid and fluorescein have also been used as tracers to visualize the distribution of sinus irrigations. These labor-intensive techniques are difficult to apply to a large sample size. They increase patient risk and commonly capture only where the irrigation fluid has been at the end of irrigation, but not the details of irrigation flow paths that would allow us to understand why the irrigation outcomes vary.

From both patients' and clinicians' perspectives, the lack of clear prediction of patient-specific irrigation outcomes can be frustrating, as clinicians prescribe a rigorous daily irrigation routine but have no assurance that what patients are doing is effective. When symptoms fail to improve after courses of irrigation, it is difficult to determine whether the added medication is not working, or the irrigation does not reach clinically relevant targets deep within the sinuses. Many patients and surgeons thus opt for systemic medication or surgery, which increases risk of overmedication, growth of resistant organisms, systemic side effects, and serious risk from surgery.

The purpose of this study was to propose a novel idea: applying three-dimensional (3D)-printing technology based on individual patients' computed tomography (CT) scans to determine an optimal personalized nasal irrigation strategy (head positions, angle of injection, flow rates, etc.).

Inclusion criteria

• Chronic rhinosinusitis without nasal polyps (CRSsNP) or Chronic rhinosinusitis with nasal polyps (CRSwNP).

Exclusion criteria

• Patients with significant nasal polyps (as determined by a clinician) were excluded upfront due to the unlikeness of irrigation penetration regardless of the head position. Patients with significant atopy, cystic fibrosis, granulomatosis with polyangiitis or other connective tissue disorder, and current pregnancy were also excluded.