OBJECTIVE: Evaluation of the metabolic demands and internal breathing environments when covering an N95 with a surgical mask (SM), cloth mask (CM), and/or face shield (FS). METHODS: Three N95 models approved by the National Institute for Occupational Safety and Health (NIOSH) were evaluated under six covering conditions using the NIOSH Automated Breathing and Metabolic Simulator. All conditions used one trial with each N95 for six incremental 5-minute work rates. Inhaled oxygen and carbon dioxide concentrations, peak inhaled and exhaled pressures, and inhaled wet bulb and dry bulb temperatures were measured continuously and averaged across all work rates and covering conditions. CONCLUSIONS: Results suggest that metabolic demands and internal breathing environments are significantly impacted by all combinations of coverings tested when compared to N95 only.

Introduction: Elevated ambient temperature and personal protective clothing (PPC) induce physiological strain which may be counteracted by heat acclimation. The purpose of this study was to determine if 5-day heat acclimation training (HAT) improves thermal and perceptual responses while wearing chemical, biological, radiological, and nuclear (CBRN) PPC. Methods: Nine healthy men completed a heat stress test (walking for one hour with CBRN PPC) in 35 degrees C and 50% relative humidity (RH) before and after 5-day HAT. The HAT consisted of five consecutive days of two 45-minute cycling sessions (50% VO2max) wearing athletic clothing separated by a 15 min rest in 45 degrees C and 20% RH. Results of the pre- and post- HAT heat stress tests were compared. Results: Heat acclimation was seen through 5-day HAT; however, thermoregulatory responses did not improve while wearing CBRN PPC. Improvement (p<0.05, day 1 vs. day 5 HAT) in skin temperature (38.0+/-0.5 degrees C vs. 37.6+/-0.5 degrees C), body temperature (38.6+/-0.4 degrees C vs. 38.3+/-0.4 degrees C), sweat rate (2.26+/-0.3kg vs. 2.64+/-0.3kg), RPE (15.8+/-2.4 vs. 13.9+/-3.1), and heat perception (5.7+/-0.6 vs. 4.9+/-1.0) were noted. However, no physiological or perceptual improvements (p>0.05) were found in the post-HAT heat stress test. Conclusions: Heat acclimation adaptations may be blunted by CBRN PPC, thus requiring differing or extended HAT.

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.

Twelve subjects wore an N95 filtering facepiece respirator (N95 FFR), one tight-fitting full facepiece powered air-purifying respirator (PAPR), two loose-fitting PAPRs, and one elastomeric/PAPR hybrid for 1 hr each during treadmill walking at 5.6 km/hr while undergoing physiological and subjective response monitoring. No significant interaction (p ≥ .05) was noted between the five respirators in heart rate, respiratory rate, oxygen saturation, transcutaneous carbon dioxide, and perceptions of breathing effort or discomfort, exertion, facial heat, and overall body heat. Respirator deadspace heat/humidity were significantly greater for the N95 FFR, whereas tympanic forehead skin temperatures were significantly greater for the hybrid PAPR. Temperature of the facial skin covered by the respirator was equivalent for the N95 FFR and hybrid PAPR, and both were significantly higher than for the other three PAPRs. Perception of eye dryness was significantly greater for a tight-fitting full facepiece PAPR than the N95 FFR and hybrid PAPR. At a low-moderate work rate over 1 hr, effects on cardiopulmonary variables, breathing perceptions, and facial and overall body heat perceptions did not differ significantly between the four PAPRs and a N95 FFR, but the tight-fitting, full facepiece PAPR increased perceptions of eye dryness. The two loose-fitting PAPRs and the full facepiece tight-fitting PAPR ameliorated exercise-induced increases in facial temperature, but this did not translate to improved perception of facial heat and overall body heat.

Purpose: to determine the correlation of umbilical temperatures (Tumb) with simultaneously recorded chest wall temperature (Tchest) and rectal temperature (Trectal) in adults during rest, heat exposure and exercise. Methods: A total of 28 healthy men, wearing different types of clothing (athletic garb, a spandex full body heating garment, firefighter bunker gear) had average and peak umbilical, chest wall and rectal temperature measurements taken during sedentary temperature stabilisation stages, heat exposure periods and active exercise phases. Results: Curvilinear relationships were noted between Tchest and Tumb compared with Trectal and their association became noticeably positive and linear at approximately 35.5degreeC. Polynomial regression analysis of Trectal with linear and quadratic forms of Tchest and Tumb indicated an overall R2 of 0.657 and 0.767, respectively. Bivariate analysis of a restricted data set (where Tchest and Tumb>35.5degree), indicated that Tumb was significantly associated with Trectal (raverage=0.710, p<0.001; rpeak=0.841, p<0.001) and Tchest was also significantly associated with Trectal, but less so (raverage=0.570, p<0.001; rpeak=0.699, p<0.001). Conclusions: the umbilicus offers a non-invasive, peripheral site for measurement of temperature that more closely correlated with body core temperature than Tchest when core temperature was >35.5degreeC.

The goal of this investigation was to evaluate the physiologic stresses of powered air-purifying respirators (PAPRs) used by workers in many industries (e.g., health care, automobile repair, public safety, building trades, etc.) during rest and three levels of energy expenditure. Twelve men and twelve women wore one tight-fitting and three loose-fitting PAPRs at rest (REST) and while walking for four minutes at oxygen consumption (V̇O(2)) rates of 1.0 l·min(-1)(LOW), 2.0 l·min(-1) (MODERATE), and 3.0 l·min(-1) or maximum (HIGH). Minimum inhaled carbon dioxide concentration (F(I)CO(2)), maximum inhaled oxygen concentration (F(I)O(2)), peak inhalation pressure, and end inhalation temperature were measured continuously breath-by-breath. Repeated measures analysis of variance found that neither the main effect of gender, nor any interactions involving gender were significant. The highest minimum F(I)CO(2) among PAPRs occurred for MODERATE and HIGH energy expenditures while wearing the loose-fitting PAPR with the largest dead space. The lowest maximum F(I)O(2) was observed during HIGH intensity energy expenditure also for the loose-fitting PAPR with the largest dead space. Among all PAPR models, peak inhalation pressures were negative at V̇O(2) > LOW, suggesting that peak inhalation flow was greater than blower flow. Results using the variables reported here suggest that PAPRs used at various levels of energy expenditure may be tolerated among healthy workers. Further research is needed to determine the source of supplemented air when inhalation flow exceeds blower flow.

PURPOSE: Monitoring and measuring core body temperature is important to prevent or minimize physiological strain and cognitive dysfunction for workers such as first responders (e.g., firefighters) and military personnel. The purpose of this study is to compare estimated core body temperature (Tco-est), determined by heart rate (HR) data from a wearable chest strap physiology monitor, to standard rectal thermometry (Tre) under different conditions. METHODS: Tco-est and Tre measurements were obtained in thermoneutral and heat stress conditions (high temperature and relative humidity) during four different experiments including treadmill exercise, cycling exercise, passive heat stress, and treadmill exercise while wearing personal protective equipment (PPE). RESULTS: Overall, the mean Tco-est did not differ significantly from Tre across the four conditions. During exercise at low-moderate work rates under heat stress conditions, Tco-est was consistently higher than Tre at all-time points. Tco-est underestimated temperature compared to Tre at rest in heat stress conditions and at a low work rate under heat stress while wearing PPE. The mean differences between the two measurements ranged from -0.1+/-0.4 to 0.3+/-0.4 degrees C and Tco-est correlated well with HR (r = 0.795 - 0.849) and mean body temperature (r = 0.637 - 0.861). CONCLUSION: These results indicate that, the comparison of Tco-est to Tre may result in over- or under-estimation which could possibly lead to heat-related illness during monitoring in certain conditions. Modifications to the current algorithm should be considered to address such issues.

BACKGROUND: To determine if hot, humid ambient conditions impact filtering facepiece respirators' (FFRs') fit, and to evaluate differences in physiologic and subjective responses between N95 FFRs and P100 FFRs. METHODS: Twelve subjects had physiologic monitoring and subjective perceptions monitored over 1 hour of treadmill exercise (5.6 km/h) in an environmental chamber (35 degrees C, relative humidity 50%) wearing an N95 FFR, P100 FFR, or no respirator. Respirator quantitative fit testing was done before and after exercise. RESULTS: There was no significant difference in pass rates for both FFRs on initial fit testing, but subjects who passed were more likely to fail the postexercise test with N95 FFRs (P = .01). Wearing FFRs increased the temperature of facial skin covered by the FFR (P = .009) and breathing discomfort (P = .002). No significant differences were noted in other measured variables (heart rate, respiratory rate, oxygen saturation, transcutaneous carbon dioxide level, rectal temperature, global skin temperature, core temperature, and subjective perceptions) between controls and FFRs and between FFR models. CONCLUSION: After 1 hour of exercise in hot, humid ambient conditions, P100 FFRs retained better fit than N95 FFRs, without additional physiologic or subjective impact. Wearing FFRs under these conditions does not add to the body's thermophysiologic or perceptual burdens.

INTRODUCTION: This study was undertaken to determine the mean peak filter resistance to airflow (Rfilter) encountered by subjects while wearing prototype filtering facepiece respirators (PRs) with low Rfilter during nasal and oral breathing at sedentary and low-moderate work rates. MATERIAL AND METHODS: In-line pressure transducer measurements of mean Rfilteracross PRs with nominal Rfilter of 29.4 Pa, 58.8 Pa and 88.2 Pa (measured at 85 l/min constant airflow) were obtained during nasal and oral breathing at sedentary and low-moderate work rates for 10 subjects. RESULTS: The mean Rfilter for the 29.4 PR was significantly lower than the other 2 PRs (p < 0.000), but there were no significant differences in mean Rfilter between the PRs with 58.8 and 88.2 Pa filter resistance (p > 0.05). The mean Rfilter was greater for oral versus nasal breathing and for exercise compared to sedentary activity (p < 0.001). CONCLUSIONS: Mean oral and nasal Rfilter for all 3 PRs was at, or below, the minimal threshold level for detection of inspiratory resistance (the 58.8-74.5 Pa/lxs-1), which may account for the previously-reported lack of significant subjective or physiological differences when wearing PRs with these low Rfilter. Lowering filtering facepiece respirator Rfilter below 88.2 Pa (measured at 85 l/min constant airflow) may not result in additional subjective or physiological benefit to the wearer.

Workers required to wear respirators must undergo additional respirator fit testing if a significant change in body weight occurs. Approximately 10% of working women of reproductive age will be pregnant and experience a significant change in weight, yet the effect of pregnancy-associated weight gain on respirator fit is unknown. Cephalo-facial anthropometric measurements and quantitative fit testing of N95 filtering facepiece respirators (N95 FFR) of 15 pregnant women and 15 matched, non-pregnant women were undertaken for comparisons between the groups. There were no significant differences between pregnant and non-pregnant women with respect to cephalo-facial anthropometric measurements or N95 FFR quantitative fit tests. Healthy pregnant workers, who adhere to the recommended weight gain limits of pregnancy, are unlikely to experience an increase in cephalo-facial dimensions that would mandate additional N95 FFR fit testing above that which is normally required on an annual basis.

BACKGROUND: Facial coverings (e.g., balaclavas, niqabs, medical/surgical masks, respirators, etc.), that impose low levels of airflow resistive loads, are worn by millions of pregnant women worldwide, but little data exist addressing their impact on pregnancy-associated cardiovascular and pulmonary responses. METHODS: 16 pregnant and 16 non-pregnant women were monitored physiologically (heart rate, blood pressure, mean arterial pressure, total peripheral resistance, stroke volume, cardiac output, oxygen saturation, transcutaneous carbon dioxide, fetal heart rate) and subjectively (exertion) for 1 h of mixed sedentary postural activity (sitting, standing) and moderate exercise (bicycle ergometer) with and without wearing N95 filtering facepiece respirators with filter resistive loads of 94.1 Pa (9.6 mm H2O) - 119.6 Pa (12.2 mm H2O) pressure. RESULTS: The external airflow resistive loads were associated with increases in diastolic pressure (p = 0.004), mean arterial pressure (p = 0.01), and subjective exertion score (p < 0.001) of all study subjects. No significant differences were noted with the external resistive loads between the pregnant and non-pregnant groups for any cardiovascular, pulmonary and subjective variable over 1 h. CONCLUSIONS: Low external airflow resistive loads, during combined sedentary postural activity and moderate exercise over 1 h, were associated with increases in the diastolic and mean arterial pressures of all study subjects, but pregnancy itself was not associated with any significant differences in physiologic or subjective responses to the external airway resistive loads utilized in the study.

To determine the impact of wearing an N95 filtering facepiece respirator (N95 FFR) on tympanic temperature measurements. TMT measurements, with and without wearing an N95 filtering facepiece respirator (N95 FFR) were obtained at the onset and termination of 1 h of treadmill exercise in 21 subjects, and at staggered time intervals (0, 20, 40, 60 min) during combined sedentary activity and exercise of another 46 subjects, to determine any effect on TMT. A total of 877 TMT measurements were obtained that demonstrated a mean TMT increase of 0.05 degrees C in the first study group (p = 0.04) and a 0.19 degrees C decrease in the second study group (p < 0.001) with the wearing of an N95 FFR, both of which were lower than controls. Wearing an N95 FFR for 1 h, at different levels of activity, results in significantly lower TMT values than not wearing an N95 FFR, but the magnitude of the changes would likely have minimal clinical significance.

BACKGROUND: To determine the physiological and subjective effects of wearing an N95 filtering facepiece respirator (N95 FFR) in advanced stages of pregnancy. METHODS: Healthy pregnant women (n = 22) and nonpregnant women (n = 22) had physiological and subjective measurements taken with and without wearing an N95 FFR during exercise and postural sedentary activities over a 1-hour period. RESULTS: There were no differences between the pregnant and nonpregnant women with respect to heart rate, respiratory rate, oxygen saturation, transcutaneous carbon dioxide level, chest wall temperature, aural temperature, and subjective perceptions of exertion and thermal comfort. No significant effect on fetal heart rate was noted. CONCLUSIONS: Healthy pregnant women wearing an N95 FFR for 1 hour during exercise and sedentary activities did not exhibit any significant differences in measured physiological and subjective responses compared with nonpregnant women.

AIM: Heat acclimation (HA) evokes numerous physiological adaptations, improves heat tolerance and has also been shown to enhance lactate (LA) responses during exercise, similar to that seen with endurance training. The purpose of this study was to examine whether HA improves the body's ability to remove LA during recovery following maximal exercise. METHODS: Ten healthy men completed two trials of maximal treadmill exercise (PRE- and POST-HA) separated by 5 days of HA. Each day of HA consisted of two 45 minute periods of cycling at ~50% VO2max separated by a 15min rest period in an environmental chamber (Tdb 45 degrees C, RH 20%). In PRE-/POST-HA trials, venous blood was collected during 60 minutes of recovery to determine LA concentrations and removal kinetics (A2: amplitude and y2: velocity constant) using bi-exponential curve fitting. RESULTS: Physiological adaptation to heat was significantly developed during HA, as evidenced by end-exercise Tre (DAY1 vs. 5) (38.89+/-0.56 vs. 38.66+/-0.44 degrees C), Tsk (38.07+/-.51 vs. 37.66+/-.48 degrees C),HR (175.0+/-9.9 vs. 165.0+/-18.5 beats.min-1), and sweat rate (1.24 +/-.26 vs. 1.47 +/-.27 L.min-1) (p<.05). However, there was no significant difference in either LA concentrations (LA0min: 8.78+/-1.08 vs. 8.69+/-1.23; LApeak: 10.97+/-1.77 vs. 10.95+/-1.46; and La60min; 2.88+/-.82 vs. 2.96+/-.93 mmol.L-1) or removal kinetics (A2: -13.05+/-7.05 vs -15.59+/-7.90 mmol.L-1 and y2: .02+/-.01 vs .03+/-.01 min-1). CONCLUSION: The present study concluded that, while effective in inducing thermo-physiological adaptations to heat stress, short-term HA does not improve the body's ability to remove LA following maximal exercise. Therefore, athletes and workers seeking faster LA recovery from intense physical activity may not benefit from short-term HA.

The mining industry is among the top ten industries nationwide with high occupational injury and fatality rates, and mine rescue response may be considered one of the most hazardous activities in mining operations. In the aftermath of an underground mine fire, explosion or water inundation, specially equipped and trained teams have been sent underground to fight fires, rescue entrapped miners, test atmospheric conditions, investigate the causes of the disaster, or recover the dead. Special personal protective ensembles are used by the team members to improve the protection of rescuers against the hazards of mine rescue and recovery. Personal protective ensembles used by mine rescue teams consist of helmet, cap lamp, hood, gloves, protective clothing, boots, kneepads, facemask, breathing apparatus, belt, and suspenders. While improved technology such as wireless warning and communication systems, lifeline pulleys, and lighted vests have been developed for mine rescuers over the last 100 years, recent research in this area of personal protective ensembles has been minimal due to the trending of reduced exposure of rescue workers. In recent years, the exposure of mine rescue teams to hazardous situations has been changing. However, it is vital that members of the teams have the capability and proper protection to immediately respond to a wide range of hazardous situations. Currently, there are no minimum requirements, best practice documents, or nationally recognized consensus standards for protective clothing used by mine rescue teams in the United States (U.S.). The following review provides a summary of potential issues that can be addressed by rescue teams and industry to improve potential exposures to rescue team members should a disaster situation occur. However, the continued trending in the mining industry toward non-exposure to potential hazards for rescue workers should continue to be the primary goal. To assist in continuing this trend, the mining industry and regulatory agencies have been more information regarding atmospheric conditions and other hazards before exposing rescue workers and others in the aftermath of a mine disaster. In light of some of the more recent mine rescuer fatalities such as the Crandall Canyon Mine and Jim Walters Resources in the past years, the direction of reducing exposure is preferred. This review provides a historical perspective on ensembles used during mine rescue operations and summarizes environmental hazards, critical elements of mine rescue ensembles, and key problems with these elements. This study also identifies domains for improved mine rescue ensembles. Furthermore, field observations from several coal mine rescue teams were added to provide the information on the currently used mine rescue ensembles in the U.S.

The purpose of this study was to evaluate the predictive capability of fabric Total Heat Loss (THL) values on thermal stress that Personal Protective Equipment (PPE) ensemble wearers may encounter while performing work. A series of three tests, consisting of the Sweating Hot Plate (SHP) test on two sample fabrics and the Sweating Thermal Manikin (STM) and human performance tests on two single-layer encapsulating ensembles (fabric/ensemble A = low THL and B = high THL), was conducted to compare THL values between SHP and STM methods along with human thermophysiological responses to wearing the ensembles. In human testing, ten male subjects performed a treadmill exercise at 4.8 km and 3% incline for 60 min in two environmental conditions (mild = 22 degrees C, 50% relative humidity (RH) and hot/humid = 35 degrees C, 65% RH). The thermal and evaporative resistances were significantly higher on a fabric level as measured in the SHP test than on the ensemble level as measured in the STM test. Consequently the THL values were also significantly different for both fabric types (SHP vs. STM: 191.3 vs. 81.5 W/m(2) in fabric/ensemble A, and 909.3 vs. 149.9 W/m(2) in fabric/ensemble B (p < 0.001). Body temperature and heart rate response between ensembles A and B were consistently different in both environmental conditions (p < 0.001), which is attributed to significantly higher sweat evaporation in ensemble B than in A (p < 0.05), despite a greater sweat production in ensemble A (p < 0.001) in both environmental conditions. Further, elevation of microclimate temperature (p < 0.001) and humidity (p < 0.01) was significantly greater in ensemble A than in B. It was concluded that: (1) SHP test determined THL values are significantly different from the actual THL potential of the PPE ensemble tested on STM, (2) physiological benefits from wearing a more breathable PPE ensemble may not be feasible with incremental THL values (SHP test) less than approximately 150-200 W.m(2), and (3) the effects of thermal environments on a level of heat stress in PPE ensemble wearers are greater than ensemble thermal characteristics.

The goal of this study was to evaluate the respiratory and metabolic stresses of air-fed ensembles used by workers in the nuclear, chemical, and pharmaceutical industries during rest, low-, and moderate-intensity treadmill exercise. Fourteen men and six women wore two different air-fed ensembles (AFE-1 and AFE-2) and one two-piece supplied-air respirator (SA) at rest (REST) and while walking for 6min at oxygen consumption (V.O2) rates of 1.0 (LOW) and 2.0 l min-1 (MOD). Inhaled CO2 (FICO2), inhaled O2 (FIO2), pressure, and temperature were measured continuously breath-by-breath. For both LOW and MOD, FICO2 was significantly lower (P < 0.03) and FIO2 was significantly greater (P < 0.008) for SA compared with AFE-1 and AFE-2 in women, while in men, similar trends were observed. Significantly lower FICO2 (P < 0.009) and significantly greater FIO2 (P < 0.04) were consistently observed in AFE-1 compared with AFE-2 in men during LOW and MOD. For both men and women, average FICO2 exceeded 2.0% in AFE-2 during MOD. During LOW and MOD, average FIO2 in AFE-1 and AFE-2 dropped <19.5% in men and women. For men and women, average inhalation pressures (PIave) were significantly greater in both air-fed ensembles than SA (P < 0.001) during REST, LOW, and MOD. Inhaled gas temperature was significantly lower in SA than in either air-fed ensemble (P < 0.001). When the air supply was shut off during walking, the time taken for minimum FICO2 to reach 2.0% was <38 s for all three ensembles in both men and women, an observation that has implications for the design of emergency escape protocols for air-fed ensemble wearers. Results show that inhaled gas concentrations may reach physiologically stressful levels in air-fed ensembles during moderate-intensity treadmill walking.

Ten subjects underwent treadmill exercise at 5.6 km/h over one hour while wearing each of three identical appearing, cup-shaped, prototype filtering facepiece respirators that differed only in their filter resistances (3 mm, 6 mm, and 9 mm H2O pressure drop). There were no statistically significant differences between filtering facepiece respirators with respect to impact on physiological parameters (i.e., heart rate, respiratory rate, oxygen saturation, transcutaneous carbon dioxide levels, tympanic membrane temperature), pulmonary function variables (i.e., tidal volume, respiratory rate, volume of carbon dioxide production, oxygen consumption, or ventilation), and subjective ratings (i.e., exertion, thermal comfort, inspiratory effort, expiratory effort and overall breathing comfort). The nominal filter resistances of the prototype filtering facepiece respirators correspond to airflow resistances ranging from 2.1 - 6.6 mm H2O/L/s which are less than, or minimally equivalent to, previously reported values for the normal threshold for detection of inspiratory breathing resistance (6 - 7.6 mm H2O/L/sec). Therefore, filtering facepiece respirators with filter resistances at, or below, this level may not impact the wearer differently physiologically or subjectively from those with filter resistances only slightly above this threshold at low-moderate work rates over one hour.

The Zephyr BioHarness was tested to determine the accuracy of heart rate (HR) and respiratory rate (RR) measurements during 2 exercise protocols in conjunction with either a laboratory metabolic cart (Vmax) or a previously validated portable metabolic system (K4b2). In one protocol, HR and RR were measured using the BioHarness and Vmax during a graded exercise up to V O2max (n=12). In another protocol, HR and RR were measured using the BH and K4b2 during sustained exercise (30% and 50% V O2max for 20 min each) in a hot environment (30 degrees C, 50% relative humidity) (n=6). During the graded exercise, HR but not RR, obtained from the BioHarness was higher compared to the Vmax at baseline and 30% V O2max (p<0.05), but showed no significant difference at other stages with high correlation coefficients for both HR (r=0.87-0.96) and RR (r=0.90-0.99 above 30% V O2max). During the exercise in the heat, there were no significant differences between the BioHarness and K4b2 system. Correlation coefficients between the methods were low for HR but moderately to highly correlated (0.49-0.99) for RR. In conclusion, the BioHarness is comparable to Vmax and K4b2 over a wide range of V O2 during graded exercise and sustained exercise in the heat.

OBJECTIVE: For pandemic influenza outbreaks, the Institute of Medicine has recommended using a surgical mask cover (SM) over N95 filtering facepiece respirators (FFRs) among healthcare workers as one strategy to avoid surface contamination of the FFR which would extend its efficacy and reduce the threat of exhausting FFR supplies. The objective of this investigation was to measure breathing air quality and breathing resistance when using FFRs with US Food and Drug Administration-cleared SM and without SM. METHODS: Thirty National Institute for Occupational Safety and Health (NIOSH)-approved FFR models with and without SM were evaluated using the NIOSH Automated Breathing and Metabolic Simulator (ABMS) through six incremental work rates. RESULTS: Generally, concentrations of average inhaled CO(2) decreased and average inhaled O(2) increased with increasing O(2) consumption for FFR+SM and FFR-only. For most work rates, peak inhalation and exhalation pressures were statistically higher in FFR+SM as compared with FFR-only. The type of FFR and the presence of exhalation valves (EVs) had significant effects on average inhaled CO(2), average inhaled O(2), and breathing pressures. The evidence suggests that placement of an SM on one type of FFR improved inhaled breathing gas concentrations over the FFR without SM; the placement of an SM over an FFR+EV probably will prevent the EV from opening, regardless of activity intensity; and, at lower levels of energy expenditure, EVs in FFR do not open either with or without an SM. CONCLUSIONS: The differences in inhaled gas concentrations in FFR+SM and FFR-only were significant, especially at lower levels of energy expenditure. The orientation of the SM on the FFR may have a significant effect on the inhaled breathing quality and breathing resistance, although the measurable inhalation and exhalation pressures caused by SM over FFR for healthcare users probably will be imperceptible at lower activity levels.

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.

Minor, but statistically significant, differences in oxygen saturation measured by pulse oximetry were noted between N95 filtering facepiece respirators with and without an exhalation valve and one model of an elastomeric air-purifying respirator worn by healthcare workers over one hour at two low work rates. Pulse oximetry determinations at the earlobe were significantly greater than concurrently obtained fingertip oximetry values, but the absolute differences were small and would presumably not be of practical significance. The use of respiratory protective equipment by healthy healthcare workers over a one hour period is not likely to result in any clinically significant oxygen desaturations.

This study evaluated the effect of exhaled moisture on the breathing resistance of three classes of filtering facepiece respirators (FFR) following 4 h of continuous wear at a breathing volume of 40 l min(-1), utilizing an automated breathing and metabolic simulator as a human surrogate. After 4 h, inhalation and exhalation resistance increased by 0.43 and 0.23 mm of H(2)O pressure, respectively, and average moisture retention in the respirators was 0.26 ml. Under ambient conditions similar to those of the current study, and at similar breathing volumes, it is unlikely that exhaled moisture will add significantly to the breathing resistance of filtering facepiece respirators (FFR) over 4 h of use.

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(CO(2)). 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(CO(2)) ≥ 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(CO(2)) is a possibility. Exhalation valve did not significantly ameliorate the FFR's P(CO(2)) impact.

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.

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.

Many studies have shown that fire fighter turnout gear and equipment may restrict mobility. The restriction of movement is usually due to a decrease in range of motion (ROM). It is important to know how much the decrease in ROM affects performance. The aim of this study was to determine the effects of fire fighter protective ensembles on mobility and performance by measuring static and dynamic range of motion (ROM) and job-related tasks. Eight healthy adults (5 males, 3 females), aged 20-40 years, participated in this study. The study consisted of measuring a battery of motions and fire fighter specific tasks while wearing a standard fire fighter ensemble (SE) or regular light clothing (baseline or BL). Several BL ROM tests were significantly (p < 0.05) different from the SE test, including a decrease in shoulder flexion, cervical rotation and flexion, trunk lateral flexion, and stand and reach. There was a significant decrease in time from SE to baseline performing the one-arm search task and object lift. These overall findings support the need for a comprehensive ergonomic evaluation of protective clothing systems to ascertain human factors issues. The development of a Standard Ergonomics Test Practice for further use in laboratories that conduct personal protective systems evaluations using human test subjects is recommended.

We evaluated the accuracy of a wearable sensor vest for real-time monitoring of physiological responses to treadmill exercise. Ten subjects in standard firefighter ensembles, treadmill exercising at 50% VO(2) max, had heart rate (HR), respiratory rate (RR), skin temperature (T(sk)), oxygen saturation (SaO(2)), tidal volume (V(T)), and minute ventilation (V(E)) recorded concurrently by a wearable plethysmographic sensor vest and standard laboratory physiological monitoring equipment for comparison. A high degree of correlation was noted for most of the measured variables [HR (r = 0.99), RR (r = 0.98), T(sk) (r = 0.98), V(E) (r = 0.88), and SaO(2) (r = 0.79)]. V(T) (r = 0.60) had a moderate correlation, although a paired differences analysis showed a mean paired difference of -0.03 L. This mean paired difference represents a 1.92% variation for V(T). Data from the wearable sensor vest is comparable to data captured from standard laboratory physiological monitoring equipment on subjects wearing standard firefighter ensembles while exercising at a moderate work rate. This study demonstrates the accuracy of the wearable sensor technology for these physiological parameters under these conditions and suggests that it could be useful for actual field studies of firefighters in traditional firefighting gear.