Physiological responses during graded treadmill exercise in chemical-resistant personal protective equipment

BACKGROUND

As the likelihood of terrorist acts increases, prehospital personnel have been forced to train in the proper use of chemical-resistant personal protective equipment (PPE). This protective ensemble has been reported to be physiologically taxing for the wearer, imposing an additional thermal load resulting in hypohydration, hyperthermia, and reduced work time. Victim extrication, the rescue-the-rescuer role of the rapid intervention team and rapid self-extrication, typically requires high-intensity work that can be maintained only for short time intervals. The additional physiological burden imparted by the level C PPE during high-intensity work is unknown.

OBJECTIVE

We hypothesized that the added thermal burden resulting from work in PPE would shorten work time and result in a higher core temperature during incremental treadmill exercise.

METHOD

In this prospective, crossover, laboratory study, EMS providers (n = 8, 5 male) completed a Bruce treadmill test on two occasions: once in a chemical-resistant coverall and air-purifying respirator (PPE) and once in shorts and t-shirt (CON). Oxygen consumption, vital signs, core and skin temperature, and perceptual measures of exertion, thermal sensation, and comfort were monitored throughout the test.

RESULTS

Subjects achieved maximal oxygen consumption and more than 90% of age-predicted maximum heart rate in both conditions. Heart rate, skin temperature, and measures of perceived exertion, comfort, and thermal sensation increased during the treadmill exercise but did not differ between the PPE and CON conditions. Core temperature increased in both the CON and PPE conditions (0.8 +/- 0.5 vs. 0.7 +/- 0.3, p = 0.40).

CONCLUSION

High-intensity work in level C PPE is primarily limited by cardiovascular capacity. The thermal burden associated with this short bout of work in PPE (approximately 10 minutes) is not different than high-intensity work in short pants and cotton t-shirt. Consideration should be given to cardiorespiratory fitness when assigning providers to work in chemical-resistant PPE, especially on tasks that require high-intensity work.

Meralgia Paresthetica Due to Body Armor Wear in U.S. Soldiers Serving in Iraq: A Case Report and Review of the Literature

Meralgia paresthetica is a disorder of the lateral femoral cutaneous nerve that results in symptoms of anterolateral thigh paresthesias and dysesthesias without associated loss of reflexes or motor weakness. Chronic meralgia paresthetica, not related to traumatic or lesion-producing compression of the nerve, is associated with obesity, pregnancy, tight-fitting garments, as well as specific duty uniform belts used by police officers and carpenters. Cases are presented in which two U.S. soldiers in Iraq experienced symptoms of meralgia paresthetica, most likely due to repetitive wear of protective body armor. Although use of protective body armor is proven to be lifesaving, modifications to improve current equipment may help to decrease morbidities such as meralgia paresthetica.

Adverse skin reactions to personal protective equipment against severe acute respiratory syndrome--a descriptive study in Singapore

Severe acute respiratory syndrome (SARS) was first recognized in February 2003. It is the first severe and readily transmissible new disease to emerge in the 21st century. Healthcare workers in affected countries were exposed to the regular use of personal protective equipment (PPE) such as the N95 mask, gloves, and gowns. Our aim was to study the prevalence of adverse skin reactions to PPE among healthcare workers in Singapore during the SARS outbreak. Healthcare staff in the National Skin Centre and Tan Tock Seng Hospital were surveyed using questionnaires. Of those asked to participate, 322 (94.7%) agreed. 14.3% of the respondents were doctors, 73.0% nurses, and 12.7% other ancillary staff. Mean age of respondents was 32.4 years, with the majority being women (85.7%) and Chinese (53.7%). 109 (35.5%) of the 307 staff who used masks regularly reported acne (59.6%), facial itch (51.4%), and rash (35.8%) from N95 mask use. 64 (21.4%) of the 299 who used gloves regularly reported dry skin (73.4%), itch (56.3%), and rash (37.5%). The use of PPE is associated with high rates of adverse skin reactions. There is a need to find suitable alternatives for affected staff and to encourage awareness among staff of the role of dermatologists in their care.

Thermophysiological responses caused by ballistic bullet-proof vests

BACKGROUND

Little data is available concerning the heat stress experienced by members of staff who wear bullet-proof vests in a warm or hot environment. For this reason, knowledge is limited and, consequently, preventative advice on how to avoid heat sickness or hyperthermia is required.

STUDY DESIGN

Skin and body temperatures, fluid loss and the heart rate of 30 persons (15 test persons versus 15 control persons) were measured in three situations typical of the test participants' job situations. Environmental data (wind velocity, air humidity, air temperature) were measured during the tests as well.

RESULTS

Whereas there was a significant increase in skin temperatures, there was no difference in the core body temperatures of both groups. Maximum core body temperature remained well below 38 degrees C in all subjects. Test persons wearing vests showed a fluid loss of 1.1 l on average (non-vest wearers in the control group 1.0 l).

CONCLUSION

There is no increased risk of heat stroke or hyperthermia for employees wearing bullet-proof vests in comparison with employees who do not wear them. Both groups, however, should be advised to ensure an adequate intake of fluid to maintain a healthy body fluid balance when working in hot environments.

Heat stress of helicopter aircrew wearing immersion suit

The objectives of the present study were to define the lowest ambient air and cabin temperatures at which aircrews wearing immersion protection are starting to experience thermal discomfort and heat stress during flight operations, and to characterize during a flight simulation in laboratory, the severity of the heat stress during exposure to a typical northern summer ambient condition (25 degrees C, 40% RH). Twenty male helicopter aircrews wearing immersion suits (insulation of 2.2 Clo in air) performed 26 flights within an 8-month period at ambient temperatures ranging between -15 and 25 degrees C, and cabin temperatures ranging between 3 and 28 degrees C. It was observed based on thermal comfort ratings that the aircrews were starting to experience thermal discomfort and heat stress at ambient and cabin air conditions above 18 degrees C and at a WBGT index of 16 degrees C. In a subsequent study, seven aircrews dressed with the same clothing were exposed for 140 min to 25 degrees C and 40% RH in a climatic chamber. During the exposure, the aircrews simulated pilot flight maneuvers for 80 min followed with backender/flight engineer activities for 60 min. By the end of the 140 min exposure, the skin temperature, rectal temperature and heart rate had increased significantly to 35.7 +/- 0.2 degrees C, 38.4 +/- 0.2 degrees C and between 110 and 160 beats/min depending on the level of physical activity. The body sweat rate averaged 0.58 kg/h and the relative humidity inside the clothing was at saturation by the end of the exposure. It was concluded that aircrews wearing immersion suits during the summer months in northern climates might experience thermal discomfort and heat stress at ambient or cabin air temperature as low as 18 degrees C.

Heat strain in cold

In spite of increased environmental cold stress, heat strain is possible also in a cold environment. The body heat balance depends on three factors: environmental thermal conditions, metabolic heat production and thermal insulation of clothing and other protective garments. As physical exercise may increase metabolic heat production from rest values by ten times or even more, the required thermal insulation of clothing may vary accordingly. However, in most outdoor work, and often in indoor cold work, too, the thermal insulation of clothing is impractical, difficult or impossible to adjust according to the changes in physical activity. This is especially true with whole body covering garments like chemical protective clothing. As a result of this imbalance, heat strain may develop. In cold all the signs of heat strain (core temperature above 38 degrees C, warm or hot thermal sensations, increased cutaneous circulation and sweating) may not be present at the same time. Heat strain in cold may be whole body heat strain or related only to torso or core temperature. Together with heat strain in torso or body core, there can be at the same time even cold strain in peripheral parts and/or superficial layers of the body. In cold environment both the preservation of insulation and facilitation of heat loss are important. Development of clothing design is still needed to allow easy adjustments of thermal insulation.

Heat strain attenuation while wearing NBC clothing: dry-ice vest compared to water spray

BACKGROUND

While wearing impermeable nuclear, biological, and chemical (NBC) clothing, reduction of thermal stress is of primary importance. We compared the effect between two cooling methods on the attenuation of heat strain.

METHODS

There were six male subjects who were divided into two groups of three and exposed on two consecutive days to 125 min of exercise in a high heat load (40 degrees C, 40% RH) wearing NBC clothing. They were cooled by one of two different cooling methods: an active cooling vest (CV) based on the sublimation of dry ice, or tap water spraying (TP).

RESULTS

After 2 h, rectal temperature (Tre) was significantly higher for the CV compared with the TP (38.1 +/- 0.04 degrees C vs. 37.7 +/- 0.10 degrees C, respectively). Skin temperature (Tsk) was significantly higher for the CV compared with the TP (36.60 +/- 0.54 degrees C vs. 34.90 +/- 0.35 degrees C, respectively). In the second hour, heart rate (HR) was significantly higher for CV compared with TP (118 +/- 13 bpm vs. 104 +/- 64 bpm, respectively). Heat storage was significantly higher after the first and second hours for the CV compared with the TP. The physiological strain index (PSI) was higher for CV compared with TP in the second hour. Sweat rate (msw) was significantly higher for CV compared with TP (560 +/- 45 g x h(-1) vs. 409 +/- 84 g x h(-1), respectively). Subjective thermal comfort was not significantly different.

CONCLUSIONS

TP was more effective than the CV in reducing heat strain under the conditions used in the study. Until a significant breakthrough in reducing heat strain while wearing NBC clothing in field conditions can be found, TP appears to be an effective and recommended cooling method.

Heat stress while wearing long pants or shorts under firefighting protective clothing

It was the purpose of this study to examine whether replacing long pants (P) with shorts (S) would reduce the heat stress of wearing firefighting protective clothing during exercise in a warm environment. Twenty-four Toronto Firefighters were allocated to one of four groups that performed heavy (H, 4.8 km x h(-1), 5% grade), moderate (M, 4.5 km x h(-1), 2.5% grade), light (L, 4.5 km x h(-1)) or very light (VL, 2.5 km x h(-1)) exercise while wearing their full protective ensemble and self-contained breathing apparatus. Participants performed a familiarization trial followed by two experimental trials at 35 degrees C and 50% relative humidity wearing either P or S under their protective overpants. Replacing P with S had no impact on the rectal temperature (Tre) or heart rate response during heavy or moderate exercise where exposure times were less than 1 h (40.8 +/- 5.8 and 53.5 +/- 9.2 min for H and M, respectively while wearing P, and 43.5 +/- 5.3 and 54.2 +/- 8.4 min, respectively while wearing S). In contrast, as exposure times were extended during lighter exercise Tre was reduced by as much as 0.4 degrees C after 80 min of exercise while wearing S. Exposure times were significantly increased from 65.8 +/- 9.6 and 83.5 +/- 11.6 min during L and VL, respectively while wearing P to 73.3 +/- 8.4 and 97.0 +/- 12.5 min, respectively while wearing S. It was concluded that replacing P with S under the firefighting protective clothing reduced the heat stress associated with wearing the protective ensemble and extended exposure times approximately 10 - 15% during light exercise. However, during heavier exercise where exposure times were less than 1 h replacing P with S was of little benefit.

Comparison of physiological and subjective strain in workers wearing two different protective coveralls for asbestos abatement tasks

The aim of this study was to compare the physiological and subjective strain in workers wearing a disposable "Tyvek" (TYV) and a ventilated "Mururoa" (MUR) coverall in a real working situation. Eleven men performing normal abatement tasks volunteered to participate. Physiological measurements included oral temperature, heart rate and sweat loss. Subjective evaluations of clothing comfort, cooling, robustness, cumbersomness, acceptable exposure duration and physical exertion were carried out at the end of the task. The ventilated MUR reduced heat strain. Indeed, it allowed significantly higher sweat loss than TYV and showed a tendency to reduce the increase in oral temperature. Subjective ratings reveal that MUR was considered better than TYV in terms of clothing comfort, coolness and robustness. On the other hand, MUR is more cumbersome to wear. In this study, where workload and heat stress were moderate, there were few differences between the two coveralls in terms of physiological strains, but far more significant differences in the subjective ratings.

Clothing as solar radiation protection

The sun is essential for life. Yet, sunlight can also be a source of such deleterious effects as sunburn, and suntanning, as well as premalignant and malignant lesions. These may all occur in individuals with normal responses to sunlight. In addition, there exist a variety of 'abnormal' photosensitivity responses to sunlight that may result from either endogenous imbalances (e.g. the porphyrias) or from added exogenous factors (e.g. drug photosensitivity). The 'normal' responses to sunlight, by and large, are produced preferentially by UVB (290-320 nm), with minor contribution by UVA (320-400 nm) wavelengths. In contrast, the 'abnormal' photosensitivity responses are, for the most part, elicited predominantly by long UVA and, in some cases, visible light. In the last 20 years or so, considerable attention has been paid to the use of fabrics as photoprotective materials. The vast majority of work in this area has been concerned with fabric protection against sunburn. In addition to in vivo measurement of fabric SPF, in vitro evaluation of fabric UPF has been carried out in numerous laboratories around the world. The UPF is estimated from the wavelength-dependent transmission of the fabric, the solar UV spectrum and the erythemal action spectrum over the wavelength region 290-400 nm. Depending on the fabric, UPF values range from 2 to several thousand. More recently, it has become clear that such environmental influences as laundering, solarization, humidity, wetting and degree of stretching may play a major role in fabric protection. Protection also may be altered by addition of dyes, UV absorbers and fluorescent whitening agents. To date, there have been relatively few studies of fabric protection for endpoints other than sunburn erythema. Yet, many fabrics that provide good protection against sunburn may provide inadequate protection against photosensitization by intrinsic or extrinsic absorbing molecules or against (pre)malignant lesions. Future work should explicity address the efficacy of protective fabrics against photosensitivity diseases that are activated by long UVA or visible wavelengths.

The utility of tympanic versus oral temperature measurements of firefighters in emergency incident rehabilitation operations

OBJECTIVES

Emergency incident rehabilitation (EIR) is the process by which firefighters receive medical screening and monitoring as well as oral rehydration while on the scene of intense or extended fire or rescue operations. A crucial parameter in EIR medical monitoring is temperature determination because heat-related illnesses are common. The objective of this study was to compare the use of oral temperature versus infrared tympanic temperature determinations of firefighters in the outdoor environment of EIR operations.

METHODS

This was a prospective observational study of firefighters participating in training scenarios involving heavy smoke and fire conditions at municipal fire training facilities. Outdoor temperature and relative humidity were obtained for each training session. Subjects were outfitted fully for fire fighting duties including full protective clothing and self-contained breathing apparatus (SCBA). Immediately on exiting the fire building, firefighters removed their SCBA masks, protective hoods, and helmets, and had simultaneous oral and tympanic temperatures taken (time 0). The subjects then sat outdoors for 10 minutes and their temperatures were again obtained (time 10). Oral and tympanic temperatures for both time points were calculated as means +/- SD. An intraclass correlation coefficient was calculated to determine how closely the simultaneously obtained oral and tympanic temperatures determinations at T-0 and T-10 correlated with each other.

RESULTS

Forty-two firefighters (mean age, 44.6 years; SD 9.6) were enrolled during four separate training days. There was poor correlation between oral and tympanic temperatures in firefighters both at time 0 (r = 0.10) and at time 10 (r = 0.18).

CONCLUSIONS

There is poor correlation between tympanic and oral temperature determinations in the EIR setting. Oral temperature determinations may be preferable to tympanic temperature determination in the EIR setting.

Dermatitis caused by physical irritants

BACKGROUND

Although physical irritant contact dermatitis (PICD) is a common occupational dermatosis, it is one of the least well understood because of its multiple types, lack of diagnostic test, and the many mechanisms involved in its production.

OBJECTIVES

To characterize the materials and mechanisms of physical irritation of the skin.

METHODS

We did a retrospective analysis over the past 20 years of all patients with a diagnosis of PICD at St John's Institute of Dermatology Contact Dermatitis Clinic.

RESULTS

Of the 29,000 patients who attended the clinic over the study period, 392 patients were diagnosed with PICD and of these, 335 files were analysed.

CONCLUSIONS

Our findings show that PICD accounted for 1.15% of all patients attending the contact clinic over the study period. Diverse occupations and materials were implicated. The most common cause of PICD was low humidity due to air-conditioning, which caused dermatitis of the face and neck in office workers due to drying out of the skin.

Heat strain reduction by ice-based and vapor compression liquid cooling systems with a toxic agent protective uniform

BACKGROUND

The purpose of this study was to compare a vapor compression microclimate cooling system (MCC) and a personal ice cooling system (PIC) for their effectiveness in reducing physiological strain when used with cooling garments worn under the impermeable self-contained toxic environment protective outfit (STEPO). A second comparison was done between the use of total body (TOTAL) and hooded shirt-only (SHIRT) cooling garments with both the MCC and PIC systems. It was hypothesized that the cooling systems would be equally effective, and total body cooling would allow 4 h of physical work in the heat while wearing STEPO.

METHODS

Eight subjects (six men, two women) attempted four experiments at 38 degrees C (100 degrees F), 30% rh, 0.9 m x sec(-1) wind, while wearing the STEPO. Subjects attempted 4 h of treadmill walking (rest/exercise cycles of 10/20 min) at a time-weighted metabolic rate of 303 +/- 50 W.

RESULTS

Exposure time was not different between MCC and PIC, but exposure time was greater with TOTAL (131 +/- 66 min) than with SHIRT (83 +/- 27 min) for both cooling systems (p < 0.05). Cooling rate was not different between MCC and PIC, but cooling rate while wearing TOTAL (362 +/- 52 W) was greater than with SHIRT (281 +/- 48 W) (p < 0.05). Average heat storage was lower with MCC (39 +/- 20 W x m(-2)) than with PIC (50 +/- 17 W x m(-2)) in both TOTAL and SHIRT (p < 0.05). Also, average heat storage while wearing TOTAL (34 +/- 19 W x m(-2)) was less than with SHIRT (55 +/- 13 W x m(-2)) for both cooling systems (p < 0.05). The Physiological Strain Index (PSI) was lower in MCC-TOTAL (2.4) than MCC-SHIRT (3.7), PIC-SHIRT (3.8), and PIC-TOTAL (3.3) after 45 min of heat exposure (p < 0.05).

CONCLUSIONS

Total body circulating liquid cooling was more effective than shirt-only cooling under the impermeable STEPO uniform, providing a greater cooling rate, allowing longer exposure time, and reducing the rate of heat storage. The MCC and PIC systems were equally effective during heat exposure, but neither system could extend exposure for the 4 h targeted time.

Helmet and shoulder pad removal in suspected cervical spine injury: human control model

STUDY DESIGN

Digital fluoroscopy was used to evaluate the motion in normal men during helmet and shoulder pad removal.

OBJECTIVES

To observe the amount of motion that occurs during the removal of helmet and shoulder pads in an uninjured spine.

SUMMARY OF BACKGROUND DATA

Removal of shoulder pads and helmet from a football player with suspected cervical spine injury can be particularly hazardous. Previous studies have been performed in cadavers with known created injuries. No control study in uninjured players has been done to show if there is similar motion with removal of football equipment.

METHODS

Four people removed the helmet and shoulder pads with a technique consistent with that described by the National Athletic Trainers' Association (NATA). Before positioning, with the helmet and shoulder pads on the subject and the subject lying flat on the table, one static lateral image was obtained as a baseline. With the neck stabilized and everyone in position, the torso, head, and neck were elevated approximately 30-40 degrees off the table bending at the waist. After elevation, continuous fluoroscopy was turned on as the helmet and shoulder pads were removed. Once the equipment was removed, the subject was carefully placed back down on the table and a final static lateral image was obtained. All images were saved digitally. Measurements were made for change in angulation, translation, distraction, and space available for the cord.

RESULTS

The results for change in disc height, translation, and space available for the cord showed no significant change. The results for change in angulation also did not show any significant motion in either flexion or extension from baseline or between each step in the protocol.

CONCLUSIONS

In the conscious player with no cervical injury the protocol used by the NATA is effective in limiting cervical motion.

A case of contact urticaria syndrome due to di(2-ethylhexyl) phthalate (DOP) in work clothes

We previously reported a case of contact urticaria syndrome (CUS) due to di(2-ethylhexyl) phthalate (DOP) in a polyvinyl chloride (PVC) grip on cotton gloves. The patient reported in this previous paper was careful not to have any contact with PVC products in his daily life or in his working environment. He discontinued the use of protective gloves with a PVC grip that was the cause of CUS. When working, he used cotton gloves without a PVC grip. We prescribed antihistamines which slightly improved his condition. However, when he wore work clothes while on duty, CUS relapsed. This condition was severe and made him feel anxious. When we advised him to wear a cotton shirt under his work clothes, the contact urticaria did not develop. We suspected that some component of the work clothes was the cause of his symptoms. A prick test with the extract solution of his work clothes showed a wheal and flare at the 15 min reading. The common component of the grip and the work clothes was found by analysis to be DOP.

[Heavy white coats are not the cause of physicians' headaches and shoulder pain]

The weight of doctors' white coats was examined and correlated to the degree of headache and muscle pain in the shoulders. The coat weight of doctors was 1.5 kg (1.1 kg-1.9 kg) (median with 25%-75% in parenthesis). The highest weight was found in the coats of young physicians 2.0 kg (1.7 kg-2.2 kg), which was higher than those of young surgeons. No correlation was seen in the degree of headache and muscle pain in the shoulders. With the long walking distances in hospitals, it would seem that internal medicine is not only an intellectually, but also a physically, demanding job.