Semi-Automated Virtual Endoscopy of the Frontal Recess.

INTRODUCTION: Virtual endoscopy (VE) is the computer-based reprocessing of diagnostic imaging to simulate endoscopy of an anatomic region of interest. VE of the Frontal Sinus Outflow Tract (FSOT) may assist surgical planning and education. METHOD: VE was performed on 16 normal sinus computed tomography (CT) scans for a total of 32 sides using the "path-to-target" tool on the TruDi surgical navigation system (ver. 2.3; Acclarent, Irving, CA, USA). To aid orientation during VE, planning points were placed on the middle turbinate, ethmoidal bulla, and skull base. The VE representation of anatomy and FSOT accuracy was manually confirmed by reviewing the corresponding orthogonal CT images and comparing them to the computed pathway. RESULTS: Of the 32 sides, the software successfully calculated the FSOT in 22 sides (69%). Of those 22 sides, the calculated FSOT, depicted in the VE sequences accurately represented the FSOT. Among sides with an accurately calculated FSOT, the VE sequences depicted a "fly-through" from a starting point in the middle meatus around various frontal recess cells to the end point in the frontal sinus. CONCLUSION: This pilot study demonstrates that software-generated VE of the FSOT is indeed feasible but requires confirmation by the surgeon for accuracy. Instances in which the software did not achieve its objective may drive further refinements of the protocol. VE of the FSOT should be explored as a tool for preoperative planning and surgical education.

Temperature-controlled radiofrequency treatment of the nasal valve in nasal airway obstruction patients with septal deviation.

KEY POINTS: Nasal valve treatment with TCRF results in NAO symptom improvement in the presence of septal deviation. Severe septal deviation does not impact the beneficial effect of TCRF nasal valve treatment. Symptoms improve with TCRF nasal valve treatment even if septal deviations involve the nasal valve.

Allergic fungal rhinosinusitis linked to other hyper-IgE syndromes through defective TH17 responses.

BACKGROUND: In a gene expression analysis comparing sinus mucosa samples from allergic fungal rhinosinusitis (AFRS) patients with samples from non-AFRS chronic rhinosinusitis with nasal polyp (CRSwNP) patients, the antimicrobial peptide (AMP) histatin 1 (HTN1) was found to be the most differentially downregulated gene in AFRS. OBJECTIVE: We sought to identify the molecular etiology of the downregulated expression of HTN1. METHODS: We used RT-PCR to compare the expression of AMPs and a fungistasis assay to evaluate the antifungal activity of sinus secretions. Using flow cytometry, we characterized the presence of TH17/TH22 cells and signal transducer and activator of transcription (STAT) signaling from AFRS patients, non-AFRS CRSwNP patients, and healthy controls. RESULTS: We confirmed decreased expression of AMPs in AFRS sinus mucosa with concordant decrease in antifungal activity in sinus secretions. IL-22 and IL-22-producing T cells were deficient within sinus mucosa of AFRS patients. In vitro studies demonstrated a defect in IL-6/STAT3 signaling critical for TH17/TH22 differentiation. Epithelial cells from AFRS patients could express AMPs when stimulated with exogenous IL-22/IL-17 and circulating TH17 cell abundance was normal. CONCLUSIONS: Similar to other hyper-IgE syndromes, but distinct from CRSwNP, AFRS patients express a defect in STAT3 activation limited to IL-6-dependent STAT3 phosphorylation that is critical for TH17/TH22 differentiation. This defect leads to a local deficiency of IL-17/IL-22 cytokines and deficient AMP expression within diseased sinus mucosa of AFRS patients. Our findings support evaluation of therapeutic approaches that enhance airway AMP production in AFRS.

Two-year outcomes of temperature-controlled radiofrequency device treatment of the nasal valve for patients with nasal airway obstruction.

Background: The objective of this study was to evaluate long-term symptom improvements in patients with nasal airway obstruction (NAO) secondary to nasal valve collapse (NVC) following minimally invasive temperature-controlled radiofrequency (TCRF) treatment. Methods: A prospective, single-arm, multicenter study in patients >18 years with NAO due to NVC. Inclusion criteria were response to nasal valve dilation (e.g., modified Cottle maneuver) and baseline Nasal Obstruction Symptom Evaluation (NOSE) Scale score ≥60. Patients were treated in the nasal valve region with a TCRF device and followed through 2 years. A responder was ≥20% reduction NOSE Scale score or ≥1 reduction in severity class. Results: A total of 122 patients were treated and 91 reached 2 years. The mean baseline NOSE Scale score was 80.3 (95% CI, 78.1-82.6). The adjusted mean change in score at 2 years was -45.8 (95% CI, -53.5 to -38.1), p < 0.001; a 57.0% improvement. The 2-year responder rate was 90.1% (95% CI, 82.3%-94.7%). Significant and sustained symptom improvement was achieved in subpopulations based on sex, age, body mass index, baseline NAO severity, nasal surgery history, NVC mechanism, septal deviation, and other anatomic contributors of NAO. No serious adverse events with a relationship to the study device and/or procedure were reported. Conclusions: Minimally invasive TCRF device treatment of the internal nasal valve for NAO is well tolerated and leads to significant and sustained improvement in NAO symptom severity through 2 years, including in patients with both static and dynamic NVC, septal deviation, turbinate enlargement, or prior nasal surgery. Level of Evidence: 2b.

Dural sinus narrowing in patients with spontaneous anterior skull base cerebrospinal fluid leak.

Objectives: Current evidence suggests a link between idiopathic intracranial hypertension (IIH) and spontaneous cerebrospinal fluid (sCSF) leak, as well as between IIH and dural venous sinus (DVS) narrowing. However, there are limited data linking DVS narrowing and sCSF leak. This study aims to determine the prevalence of DVS narrowing in patients with sCSF leak. Methods: A retrospective review of all patients with sCSF leak that presented to a tertiary academic center from 2008 to 2019. Preoperative imaging was independently reviewed by two neuroradiologists to evaluate for DVS narrowing. Available literature was used to estimate the prevalence of DVS narrowing in the general population to allow for comparison. Data were analyzed using Exact binomial test. Results: Analysis of 25 patients with appropriate imaging revealed the majority were women (21/25, 84%) with a mean age of 51.89 years (SD 13.96). The majority of these patients were found to have narrowing of the DVS (20/25, 80%). In patient with sCSF leaks, there was a significantly higher proportion of patients with DVS narrowing compared with published literature examining this condition in the general population (80% vs. 40%, CI 0.59-0.93, p < .001). Conclusion: The prevalence of DVS narrowing in patients with sCSF leaks is substantial and likely greater than the general population. Moreover, there appears to be narrowing in most patients with sCSF leak. Preoperative radiological evaluation of the DVS using MR venography may be useful in patients with sCSF leaks as DVS stenosis may be an underdiagnosed etiology. Further study is needed to evaluate this. Level of Evidence: IV.

Antiplatelet and anticoagulation therapy and the risk of pituitary apoplexy in pituitary adenoma patients.

PURPOSE: Pituitary apoplexy can be a life threatening and vision compromising event. Antiplatelet and anticoagulation use has been reported as a contributing factor in pituitary apoplexy (PA). Utilizing one of the largest cohorts in the literature, this study aims to determine the risk of PA in patients on antiplatelet/anticoagulation (AP/AC) therapy. METHODS: A single center, retrospective study was conducted on 342 pituitary adenoma patients, of which 77 patients presented with PA (23%). Several potential risk factors for PA were assessed, including: patient demographics, tumor characteristics, pre-operative hormone replacement, neurologic deficits, coagulation studies, platelet count, and AP/AC therapy. RESULTS: Comparing patients with and without apoplexy, there was no significant difference in the proportion of patients taking aspirin (45 no apoplexy vs. 10 apoplexy; p = 0.5), clopidogrel (10 no apoplexy vs. 4 apoplexy; p = 0.5), and anticoagulation (7 no apoplexy vs. 3 apoplexy; p = 0.7). However, male sex (p-value < 0.001) was a predictor for apoplexy while pre-operative hormone treatment was a protective factor from apoplexy (p-value < 0.001). A non-clinical difference in INR was also noted as a predictor for apoplexy (no apoplexy: 1.01 ± 0.09, apoplexy: 1.07 ± 0.15; p < 0.001). CONCLUSIONS: Although pituitary tumors have a high risk for spontaneous hemorrhage, the use of aspirin is not a risk for hemorrhage. Our study did not find an increased risk of apoplexy with clopidogrel or anticoagulation, but further investigation is needed with a larger cohort. Confirming other reports, male sex is associated with an increased risk for PA.

Determinants of physician assessment of chronic rhinosinusitis disease control using EPOS 2020 criteria and the importance of incorporating patient perspectives of disease control.

BACKGROUND: We identify chronic rhinosinusitis (CRS) manifestations associated with how rhinologists assess CRS control, with a focus on patient perspectives (patient-reported CRS control). METHODS: Fifteen rhinologists were provided with real-world data from 200 CRS patients. Participating rhinologists first classified patients' CRS control as "controlled," "partly controlled," and "uncontrolled" using seven CRS manifestations reflecting European Position Paper on Rhinosinusitis and Nasal Polyps (EPOS) CRS control criteria (nasal obstruction, drainage, impaired smell, facial pain/pressure, sleep disturbance, use of systemic antibiotics/corticosteroids in past 6 months, and nasal endoscopy findings) and patient-reported CRS control. They then classified patients' CRS control without knowledge of patient-reported CRS control. Interrater reliability and agreement of rhinologist-assessed CRS control with patient-reported CRS control and EPOS guidelines were determined. RESULTS: CRS control classification with and without knowledge of patient-reported CRS control was highly consistent across rhinologists (κw  = 0.758). Rhinologist-assessed CRS control agreed with patient-reported CRS control significantly better when rhinologists had knowledge of patient-reported CRS control (κw  = 0.736 vs. κw  = 0.554, p < 0.001). Patient-reported CRS control, nasal obstruction, drainage, and endoscopy findings were most strongly associated with rhinologists' assessment of CRS control. Rhinologists' CRS control assessments weakly agreed with EPOS CRS control guidelines with (κw  = 0.529) and without (κw  = 0.538) patient-reported CRS control. Rhinologists classified CRS as more controlled than EPOS guidelines in almost 50% of cases. CONCLUSIONS: This study directly demonstrates the importance of patient-reported CRS control as a dominant influence on rhinologists' CRS control assessment. Knowledge of patient-reported CRS control may better align rhinologists' CRS control assessments and treatment decisions with patients' perspectives.

Neurofibroma of the internal carotid artery cavernous sympathetic plexus: illustrative case.

BACKGROUND: Intracranial carotid sympathetic plexus (CSP) nerve sheath tumors have rarely been reported in the literature. This study describes the first reported case of a CSP neurofibroma and the first case of a CSP nerve sheath tumor treated via an endoscopic endonasal approach followed by adjuvant radiosurgery. OBSERVATIONS: A 53-year-old man presented with 3 days of headaches and diplopia and was found to have a complete left abducens nerve palsy. Computed tomography (CT) revealed a smoothly dilated left carotid canal, CT angiography revealed a superiorly displaced left internal carotid artery (ICA), and magnetic resonance imaging revealed a T2-hyperintense and avidly enhancing lesion in the left cavernous sinus encasing the ICA. The patient underwent subtotal resection via an endoscopic transsphenoidal transcavernous approach followed by Gamma Knife radiosurgery. LESSONS: Nerve sheath tumors arising from the CSP are extremely rare but need to be considered when assessing unusual cavernous sinus lesions. The clinical presentation is dependent on the anatomical location of the tumor and its relationship to the ICA. The optimal treatment paradigm is unknown.

Improving the Accuracy of Maxillary Sinus Balloon Dilation Using Virtual Reality Navigation: A Proof-of-Concept Study.

BACKGROUND: The ability to reliably and accurately cannulate the natural ostium of the maxillary sinus during balloon sinus dilation (BSD) has been criticized. Conventional computed tomography (CT)-guided navigation systems are helpful when dilating other sinuses, but they fail to provide meaningful feedback to guide accurate dilation of the maxillary sinus. OBJECTIVE: This study explores the potential impact of a new navigation system with virtual reality (VR) functionality on successful BSD of the maxillary sinus. METHODS: Using the established methodology, a cadaveric evaluation of the accuracy of maxillary BSD with a VR-equipped navigation system and balloon was undertaken. The natural ostium was landmarked on CT images with a beacon, and a VR intrasinus camera view was used to guide balloon dilation by a team of 2 rhinologists. Following the procedure, uncinectomies were performed to directly assess the accuracy of dilation. Standardized video clips with a 30° endoscopic view of the area were reviewed by 3 blinded rhinologists from different institutions who were not part of the procedures. Dilation of the natural ostium was scored as "successful," "unsuccessful," or "unsure." RESULTS: Sixteen maxillary BSDs were completed in 8 cadavers using VR navigation. The medial wall of the maxillary sinus showing the natural ostium as well as any accessory ostia were readily visualized and labeled with a beacon in all cases using the 3D virtual rendering feature. Dilations were scored using a standardized rubric. Any "unsure" responses from the reviewers were categorized as "unsuccessful" for analysis purposes. The accuracy rate for dilation of the maxillary sinus natural ostium was 77%. Despite the use of cadaveric tissues, a fair interrater agreement (kappa 0.21) was achieved. CONCLUSION: Using VR navigation appears to improve the accuracy of cannulating the natural ostium during maxillary BSD, which could lead to better outcomes. Further study in live subjects is warranted.

Individual SNOT-22 Items Aid in Differentiating Between Spontaneous Cerebrospinal Fluid Rhinorrhea and Chronic Rhinosinusitis Without Nasal Polyps.

OBJECTIVES: Spontaneous cerebrospinal fluid (CSF) rhinorrhea is a diagnostic challenge due to its overlapping symptomatology with other sinonasal diseases. The objective of this study was to investigate whether items on the sinonasal outcome test (SNOT)-22 could suggest a diagnosis of spontaneous CSF rhinorrhea versus chronic rhinosinusitis without nasal polyps (CRSsNP). METHODS: A multi-institutional retrospective chart review of patients with spontaneous CSF rhinorrhea and a control group of CRSsNP patients was performed. Individual SNOT-22 scores and domain scores were compared. RESULTS: One hundred fifteen patients were included in both cohorts. Of the patients in the CSF rhinorrhea group, 48% were misdiagnosed as chronic rhinosinusitis (CRS) prior to the correct identification of a CSF leak. On bivariate analysis, the CSF rhinorrhea group scored significantly higher on the SNOT-22 for runny nose (P < .001) and was more likely to designate this symptom as most important (P < .001). The CRSsNP group scored significantly higher in nasal blockage (P < .001), thick nasal discharge (P < .001), facial pain/pressure (P < .001), and in the ear/facial (P < .001) and rhinologic (P = .003) domains. Multivariable logistic regression revealed that runny nose (P < .001) was most predictive of spontaneous CSF rhinorrhea while nasal blockage (P < .001), thick nasal discharge (P < .001), and facial pain/pressure (P = .001) were predictive of CRSsNP after adjusting for relevant confounders. No significant difference was observed in total SNOT-22 scores between groups (P = .676). CONCLUSIONS: Spontaneous CSF rhinorrhea is commonly misdiagnosed as other sinonasal pathologies. However, individual SNOT-22 items can help aid in suggesting a CSF leak. Spontaneous CSF rhinorrhea should be suspected in patients who have high SNOT-22 scores for runny nose and report this symptom as most important, but have lower scores related to the other cardinal symptoms of CRS.

SNOT-22 Quality of Life Scores Improve After Endoscopic Endonasal Repair of Spontaneous Cerebrospinal Fluid Rhinorrhea.

OBJECTIVES: Patients with spontaneous cerebrospinal fluid (CSF) rhinorrhea can experience significant sinonasal symptom burden, leading to poor quality of life (QOL). The objective of this study was to investigate sinonasal outcome test-22 (SNOT-22) scores in patients undergoing endoscopic endonasal surgery for spontaneous CSF rhinorrhea and compare them to patients undergoing endoscopic sinus surgery (ESS) for chronic rhinosinusitis without nasal polyps (CRSsNP). METHODS: A multi-institutional retrospective review of patients with spontaneous CSF rhinorrhea and CRSsNP was performed. Pre-surgery and post-surgery SNOT-22 scores and domains were compared within each group. Improvements in SNOT-22 scores after surgery were compared between the groups. RESULTS: Ninety-one patients were in the CSF rhinorrhea group and 105 patients were in the CRSsNP group. Within each group, surgery significantly improved total SNOT-22 scores, domain scores, and most of the individual symptoms. Comparing the 2 groups revealed similar improvements in total SNOT-22 scores (P = .244). The CSF rhinorrhea group improved more in runny nose (P < .001), postnasal discharge (P < .001), wake up at night (P = .024), and embarrassed (P = .002). The CRSsNP group improved more in sneezing (P = .027), nasal blockage (P < .001), decreased sense of smell/taste (P = .011), thick nasal discharge (P < .001), facial pain/pressure (P = .008), and the ear/facial domain (P = .010). CONCLUSIONS: Patients with spontaneous CSF rhinorrhea experience significant symptom burden. Those who undergo CSF leak repair should experience significant improvement in QOL similar to patients who undergo ESS for CRSsNP as measured by SNOT-22.

Three-Dimensional Printed Models to Accelerate Resident Surgical Learning Curve for Standard Endoscopic Sinus Surgery Techniques.

Background: Endoscopic sinus surgery presents significant visuospatial challenges to surgical trainees. We tested the utility of novel 3D printed models to simulate sinus surgery tasks to improve endoscopic skillsets in resident trainees. Methods: This was a prospective quality improvement study of 10 ENT residents (PGY1-5). Participants rotated through 4 stations with different 3D simulation training modules designed to enhance endoscopic skillsets in the axial, sagittal and coronal planes (e.g., straight forceps to grasp a bead from a ledge, angled instruments to cannulate openings). Participants completed a self-assessment survey on the subjective sinus surgical skills using a visual analog scale before and after tasks. Two- tailed paired T-tests were used to analyze the data. Results: All residents rated their post-intervention "overall sinus surgery skills" higher than pre-intervention. They rated simulations to provide more significant utility as an adjunct to surgical education after the intervention. All but one participant reported improved spatial awareness working with the endoscopes and surgical instruments. There was subjectively improved proficiency in using 0-degree and angled endoscopes as well as cutting, grasping, and curved instruments after the intervention. The simulations led to subjective improvements in spatial awareness, bimanual dexterity, and increased confidence in selecting correct surgical instruments. Conclusion: Our set of novel 3D printed models to improve sinus surgery skillset was well accepted by the resident cohort. The 3D models can serve as an adjunct tool to traditional residency education.

Are nonsteroidal anti-inflammatory drugs effective enough for postoperative pain control after functional endoscopic sinus surgery and septoplasty? A randomized, controlled study.

BACKGROUND: Endoscopic sinus surgery (ESS) and septoplasty are commonly performed procedures without standardized postoperative pain regimens. There is reluctance to prescribe opioids for postoperative pain given their potential for abuse. Nonsteroidal anti-inflammatory drugs (NSAIDs) have been demonstrated to reduce or even obviate the need for opioid pain medications after otolaryngologic surgeries, but prospective validation is lacking. METHODS: A randomized, controlled study comparing the efficacy of diclofenac sodium to hydrocodone/acetaminophen (APAP) after ESS with or without septoplasty was performed. Participants were given a 100-mm visual analog pain scale (VAS) at postoperative days (PODs) 1, 2, 3, and 5 after ESS. Two-sample t tests were used to compare pain scores between groups. RESULTS: One hundred patients enrolled, and 74 patients provided pain scores to the survey. Pain was greatest for both groups on POD 1. Treatment with diclofenac sodium vs hydrocodone/APAP did not statistically impact pain scores at PODs 1, 2, 3, or 5. No cases of epistaxis requiring an emergency room visit or return to the operating room were noted during the study period. CONCLUSION: Diclofenac sodium may be non-inferior to hydrocodone/APAP in treating pain after ESS with or without septoplasty in opioid naive patients without pre-existing pain conditions. Further studies with larger samples are warranted to investigate the potential superiority of diclofenac to hydrocodone/APAP in certain patients after ESS and septoplasty.

Contour Map Point Distribution and Surgeon Experience Level Affect Accuracy of Surgical Navigation in a Pilot Study.

BACKGROUND: Reliable use of surgical navigation depends upon the registration process. The gold standard is paired-point registration with bone-anchored fiducials, but contour-map registration is more practical. Surgeons may employ variable contour maps and less experienced team members often perform this critical step. The impact of these practices on target registration error (TRE) is not well-studied. METHODS: A dry lab set-up consisting of a navigation system (Fusion ENT, Medtronic, Jacksonville, FL) and a sinus phantom with 2 mm radiopaque spheres in the sphenoid and ethmoid regions was developed. A CT (0.625 mm slice thickness) was obtained. Registration was performed with a contour-based protocol. Accuracy was determined using the software's distance measurement tool. Registration was performed with narrow-field (NF; forehead points medial to the mid-pupillary line) and wide field (WF; entire forehead) contour maps. An experienced rhinologist and a resident surgeon performed each registration in triplicate and TRE at the sphenoid and ethmoid markers was measured in triplicate. RESULTS: WF mapping had a lower TRE than NF (1.09 mm [95% Confidence Interval (CI) 0.96-1.22] vs 1.68 mm [95% CI 1.50-1.86]). The experienced surgeon had a lower TRE compared to the resident (1.21 mm [95% CI 1.08-1.34] vs 1.54 mm [95% CI 1.35-1.74]). CONCLUSIONS: In this navigation model, wide field mapping offers better accuracy than narrow-field mapping, and an experienced surgeon seemed to achieve better accuracy than a resident surgeon. These observations have potential implications for the use of this technology in the operating room.

Hydraulic dissection technique during endoscopic sinus surgery using a novel balloon sinus dilation device.

BACKGROUND: More than a decade after its introduction, some rhinologic surgeons have incorporated the technique of balloon sinus dilation (BSD) technology into "hybrid" endoscopic sinus surgery (ESS) procedures. A novel BSD device which can be placed over standard surgical instruments, including surgical navigation instruments, has recently been introduced. We present a case series in which this device was used as a hydraulic dissection tool to aid safe efficient surgery in difficult-to-access locations of the paranasal sinuses during hybrid ESS procedures. OBJECTIVE: Highlight the potential role of hydraulic dissection techniques during ESS utilizing BSD. METHODS: Retrospective case series of patients who underwent ESS performed in part with a novel BSD device. RESULTS: A total of 10 patients who underwent hybrid ESS with BSD were reviewed. In all 10 cases, the novel BSD device was used without complication. The device was used over straight and curved suctions while being tracked with surgical navigation in all cases. Thirteen posterior ethmoid dissections, 12 sphenoidotomies, and 8 frontal sinusotomies were assisted with the device. For the selected dissections in which the balloon was utilized, the operating surgeon found it to be helpful in creating more space in difficult to access areas which allowed for continued safe surgical dissection. CONCLUSIONS: Sinus balloon devices can be used as a hydraulic dissection tool and may be a useful adjunct during ESS. The novel dilation system used in this study, which deploys a sinus balloon device over standard surgical instruments with surgical navigation, provides even more opportunity to accurately dissect difficult areas of the paranasal sinuses safely and efficiently. Further studies evaluating the exact role of sinus balloon devices used as a hydraulic dissection tool during ESS are warranted. LEVEL OF EVIDENCE: 4.

Revisiting the controversy: The role of fungi in chronic rhinosinusitis.

In the last two decades, the development of culture-independent genomic techniques has facilitated an increased appreciation of the microbiota-immunity interactions and their role in a multitude of chronic inflammatory diseases such as chronic rhinosinusitis (CRS), asthma, inflammatory bowel disease and dermatitis. While the pathologic role of bacteria in chronic inflammatory diseases is generally accepted, the understanding of the role of fungi remains controversial. Chronic rhinosinusitis, specifically the phenotype linked to nasal polyps, represents a spectrum of chronic inflammatory diseases typically characterized by a type 2 immune response. Studies on the microbiota within sinus cavities from healthy and diseased patients have focused on the bacterial community, mainly highlighting the loss of diversity associated with sinus inflammation. Within the various CRS with nasal polyps (CRSwNP) phenotypes, allergic fungal rhinosinusitis presents an opportunity to investigate the role of fungi in chronic type 2 immune responses as well as the antifungal immune pathways designed to prevent invasive fungal diseases. In this review, we examine the spectrum of fungi-associated sinus diseases highlighting the interaction between fungal species and host immune status on disease presentation. With a focus on fungi and type 2 immune response, we highlight the current knowledge and its limitations of the sinus mycobiota along with cellular interactions and activated molecular pathways linked to fungi.

N95 respirator reuse, decontamination methods, and microbial burden: A randomized controlled trial.

PURPOSE: To evaluate the effectiveness and ease of N95 respirator decontamination methods in a clinic setting and to identify the extent of microbial colonization on respirators associated with reuse. METHODS: In a prospective fashion, N95 respirators (n = 15) were randomized to a decontamination process (time, dry heat, or ultraviolet C light [UVC]) in outpatient clinics. Each respirator was re-used up to 5 separate clinic sessions. Swabs on each respirator for SARS-CoV-2, bacteria, and fungi were obtained before clinic, after clinic and post-treatment. Mask integrity was checked after each treatment (n = 68). Statistical analyses were performed to determine factors for positive samples. RESULTS: All three decontamination processes reduced bacteria counts similarly. On multivariate mixed model analysis, there were an additional 8.1 colonies of bacteria (95% CI 5.7 to 10.5; p < 0.01) on the inside compared to the outside surface of the respirators. Treatment resulted in a decrease of bacterial load by 8.6 colonies (95% CI -11.6 to -5.5; p < 0.01). Although no decontamination treatment affected the respirator filtration efficiency, heat treatments were associated with the breakdown of thermoplastic elastomer straps. Contamination with fungal and SARS-CoV-2 viral particles were minimal to non-existent. CONCLUSIONS: Time, heat and UVC all reduced bacterial load on reused N95 respirators. Fungal contamination was minimal. Heat could permanently damage some elastic straps making the respirators nonfunctional. Given its effectiveness against microbes, lack of damage to re-treated respirators and logistical ease, UVC represents an optimal decontamination method for individual N95 respirators when reuse is necessary.