Project BREATHE - Prototype Respirator Evaluation Utilizing Newly Proposed Respirator Test Criteria.

Machine and human subject testing of four prototype filtering facepiece respirators (FFR) and two commercial FFR was carried out utilizing recently proposed respirator test criteria that address healthcare worker-identified comfort and tolerance issues. Overall, two FFR (one prototype, one commercial model) were able to pass all eight criteria and three FFR (two prototypes, one commercial model) were able to pass seven of eight criteria. One prototype FFR was not tested against the criteria due to an inability to obtain satisfactory results on human subject quantitative respirator fit testing. Future studies, testing different models and styles of FFR against the proposed criteria, will be required to gauge the overall utility and effectiveness of the criteria in determining FFR comfort and tolerance issues that may impact user compliance and, by extension, protection.

Speech intelligibility assessment of protective facemasks and air-purifying respirators.

Speech Intelligibility (SI) is the perceived quality of sound transmission. In healthcare settings, the ability to communicate clearly with coworkers, patients, etc., is crucial to quality patient care and safety. The objectives of this study were to: (1) assess the suitability of the Speech Transmission Index (STI) methods for testing reusable and disposable facial and respiratory personal protective equipment (protective facemasks [PF], N95 filtering facepiece respirators [N95 FFR], and elastomeric half-mask air-purifying respirators [EAPR]) commonly worn by healthcare workers; (2) quantify STI levels of these devices; and (3) contribute to the scientific body of knowledge in the area of SI. SI was assessed using the STI under two experimental conditions: (1) a modified version of the National Fire Protection Association 1981 Supplementary Voice Communications System Performance Test at a Signal to Noise Ratio (SNR) of -15 (66 dBA) and (2) STI measurements utilizing a range of modified pink noise levels (52.5 dBA (-2 SNR) - 72.5 dBA (+7 SNR)) in 5.0 dBA increments. The PF models (Kimberly Clark 49214 and 3 M 1818) had the least effect on SI interference, typically deviating from the STI baseline (no-mask condition) by 3% and 4% STI, respectively. The N95FFR (3 M 1870, 3 M 1860) had more effect on SI interference, typically differing from baseline by 13% and 17%, respectively, for models tested. The EAPR models (Scott Xcel and North 5500) had the most significant impact on SI, differing from baseline by 42% for models tested. This data offers insight into the performance of these apparatus with respect to STI and may serve as a reference point for future respirator design considerations, standards development, testing and certification activities.

Effect of upper strap downward displacement on n95 filtering facepiece respirator fit factors: a pilot study.

Fifteen subjects underwent three replicates of quantitative respirator fit-testing with N95 filtering facepiece respirators that were donned with the upper strap high on the occiput, as per the manufacturers' donning instructions. Each fit-test was immediately followed by repeat fit-testing with the upper strap downwardly displaced to the level of the ear sulcus to determine any change in fit factors that might occur with upper strap downward slippage. A total of 35/45 (78%) initial fit-tests had a passing score (fit factor ≥ 100) with the top strap high on the occiput and 33/35 (94%) of these passed subsequent fit-testing after the top strap was displaced downward to the ear sulcus. Geometric mean fit factors for the initial passed fit-tests, and following downward strap displacement, were 217 ± 1.6 and 207 ± 1.9, respectively (p = 0.64). Downward displacement of the top strap did not significantly impact fit factors of N95 FFRs that had previously passed fit-testing.

Development of an advanced respirator fit-test headform.

Improved respirator test headforms are needed to measure the fit of N95 filtering facepiece respirators (FFRs) for protection studies against viable airborne particles. A Static (i.e., non-moving, non-speaking) Advanced Headform (StAH) was developed for evaluating the fit of N95 FFRs. The StAH was developed based on the anthropometric dimensions of a digital headform reported by the National Institute for Occupational Safety and Health (NIOSH) and has a silicone polymer skin with defined local tissue thicknesses. Quantitative fit factor evaluations were performed on seven N95 FFR models of various sizes and designs. Donnings were performed with and without a pre-test leak checking method. For each method, four replicate FFR samples of each of the seven models were tested with two donnings per replicate, resulting in a total of 56 tests per donning method. Each fit factor evaluation was comprised of three 86-sec exercises: "Normal Breathing" (NB, 11.2 liters per min (lpm)), "Deep Breathing" (DB, 20.4 lpm), then NB again. A fit factor for each exercise and an overall test fit factor were obtained. Analysis of variance methods were used to identify statistical differences among fit factors (analyzed as logarithms) for different FFR models, exercises, and testing methods. For each FFR model and for each testing method, the NB and DB fit factor data were not significantly different (P > 0.05). Significant differences were seen in the overall exercise fit factor data for the two donning methods among all FFR models (pooled data) and in the overall exercise fit factor data for the two testing methods within certain models. Utilization of the leak checking method improved the rate of obtaining overall exercise fit factors ≥100. The FFR models, which are expected to achieve overall fit factors ≥ 100 on human subjects, achieved overall exercise fit factors ≥ 100 on the StAH. Further research is needed to evaluate the correlation of FFRs fitted on the StAH to FFRs fitted on people. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a file providing detailed information on the advanced head form design and fabrication process.].

Impact of multiple consecutive donnings on filtering facepiece respirator fit.

BACKGROUND: A concern with reuse of National Institute for Occupational Safety and Health-certified N95 filtering facepiece respirators (FFRs) is that multiple donnings could stress FFR components, impairing fit. This study investigated the impact of multiple donnings on the facepiece fit of 6 N95 FFR models using a group of 10 experienced test subjects per model. METHODS: The TSI PORTACOUNT Plus and N95 Companion accessory were used for all tests. After qualifying by passing a standard Occupational Safety and Health Administration fit test, subjects performed up to 20 consecutive tests on an individual FFR sample using a modified protocol. Regression analyses were performed for the percentage of donnings resulting in fit factors (FFs) ≥100 for all 6 FFR models combined. RESULTS: Regression analyses showed statistical significance for donning groups 1-10, 1-15, and 1-20. The mean percentage of donnings with an FF ≥100 was 81%-93% for donning group 1-5, but dropped to 53%-75% for donning group 16-20. CONCLUSIONS: Our results show that multiple donnings had a model-dependent impact on fit for the 6 N95 models evaluated. The data suggest that 5 consecutive donnings can be performed before FFs consistently drop below 100.

Infrared imaging for leak detection of N95 filtering facepiece respirators: a pilot study.

BACKGROUND: This study was undertaken to determine the utility of an infrared camera (IRC) for assessing leaks around filtering facepiece respirators (FFR) during quantitative respirator fit testing. METHODS: Eight subjects underwent quantitative fit testing on six N95 FFR models (48 total fit tests) while simultaneously being recorded with an IRC. RESULTS: The IRC detected 49 exhalation leaks during 39 tests and no leaks in nine tests. Exhalation leaks were identified in all failed fit tests (13) and a majority (26 of 35) of passed tests. Anatomically, the nasal region and malar (cheekbone) regions accounted for 71% of identified leak sites. Fit factors for fit tests without identified exhalation leaks were significantly higher than fit tests with leaks detected by IRC (P = 0.01). CONCLUSIONS: Thermal imaging using IRC can detect leaks in respiratory protective equipment and has the potential as a screening tool for assessment of the adequacy of post-donning FFR fit.

Physiological impact of the N95 filtering facepiece respirator on healthcare workers.

OBJECTIVE: To assess the physiological impact of the N95 filtering facepiece respirator (FFR) on healthcare workers. METHODS: Ten healthcare workers each conducted multiple 1-hour treadmill walking sessions, at 1.7 miles/h, and at 2.5 miles/h, while wearing FFR with exhalation valve, FFR without exhalation valve, and without FFR (control session). We monitored heart rate, respiratory rate, tidal volume, minute volume, blood oxygen saturation, and transcutaneously measured P(CO2). We also measured user comfort and exertion, FFR moisture retention, and the carbon dioxide and oxygen concentrations in the FFR's dead space. RESULTS: There were no significant differences between FFR and control in the physiological variables, exertion scores, or comfort scores. There was no significant difference in moisture retention between FFR with and without exhalation valve. Two subjects had peak P(CO2) > or = 50 mm Hg. The FFR with exhalation valve offered no benefit in physiological burden over the FFR without valve. The FFR dead-space oxygen and carbon dioxide levels did not meet the Occupational Safety and Health Administration's ambient workplace standards. CONCLUSIONS: In healthy healthcare workers, FFR did not impose any important physiological burden during 1 hour of use, at realistic clinical work rates, but the FFR dead-space carbon dioxide and oxygen levels were significantly above and below, respectively, the ambient workplace standards, and elevated P(CO2) is a possibility. Exhalation valve did not significantly ameliorate the FFR's P(CO2) impact.

Reusable elastomeric air-purifying respirators: physiologic impact on health care workers.

BACKGROUND: Elastomeric air-purifying respirators offer the benefit of reusability, but their physiological impact on health care workers is unknown. METHODS: Ten health care workers exercised at 2 health care-associated work rates wearing an elastomeric air-purifying respirator. Mixed inhalation/exhalation respirator dead space gases (oxygen, carbon dioxide) were sampled, and physiological parameters were monitored (heart rate, breathing rate, tidal volume, minute volume, oxygen saturation, transcutaneous carbon dioxide). Numerical rating scales were used to evaluate comfort and exertion. RESULTS: Compared with controls (no respirator), significant decreases in the breathing rate at both work rates (P < .05) and increases in tidal volume at the lower work rate (P < .01) were noted with respirator use. Approximately half the subjects had transcutaneous carbon dioxide levels above the upper limit of normal after 1 hour of use. Although well tolerated, comfort was negatively impacted by elastomeric air-purifying respirators wear. CONCLUSION: Reusable elastomeric air-purifying respirators impose little additional physiological burden over the course of 1 hour at usual health care work rates. However, the potential for carbon dioxide retention in a significant proportion of users exists and requires further investigation.

Surgical mask placement over N95 filtering facepiece respirators: physiological effects on healthcare workers.

BACKGROUND AND OBJECTIVE: Filtering facepiece respirators ('N95 Masks') may be in short supply during large-scale infectious outbreaks. Suggestions have been made to extend their useful life by using a surgical mask as an outer barrier, but the physiological impact of this added barrier upon the wearer has not been studied. METHODS: A surgical mask was worn over an N95 filtering facepiece respirator by 10 healthcare workers for 1 h at each of two work rates. Heart rate, respiratory rate, tidal volume, minute volume, oxygen saturation, transcutaneous carbon dioxide levels and respirator dead space gases were monitored and compared with controls (N95 filtering facepiece respirator without a surgical mask). Subjective perceptions of exertion and comfort were assessed by numerical rating scales. RESULTS: There were no significant differences in physiological variables between those who used surgical masks and controls. Surgical masks decreased dead space oxygen concentrations of the filtering facepiece respirators at the lesser work rate (P = 0.03) and for filtering facepiece respirators with an exhalation valve at the higher work rate (P = 0.003). Respirator dead space oxygen and carbon dioxide levels were not harmonious with Occupational Safety and Health Administration workplace ambient atmosphere standards. Exertion and comfort scores were not significantly impacted by the surgical mask. CONCLUSIONS: Use of a surgical mask as an outer barrier over N95 filtering facepiece respirators does not significantly impact the physiological burden or perceptions of comfort and exertion by the wearer over that experienced without use of a surgical mask.