Joe Suyama

Comparison of Active Cooling Devices with Passive Cooling for Rehabilitation of Firefighters Performing Exercise in Thermal Protective Clothing: A Report from the Fireground Rehab Evaluation (FIRE) Trial

Abstract Background. Thermal protective clothing (TPC) worn by firefighters provides considerable protection from the external environment during structural fire suppression. However, TPC is associated with physiologic derangements that may have adverse cardiovascular consequences. These derangements should be treated during on-scene rehabilitation periods. Objective. To examine heart rate and core temperature responses during the application of four active cooling devices, currently being marketed to the fire service for on-scene rehabilitation, and compare them with passive cooling in a moderate temperature (approximately 24°C) and with an infusion of cold (4°C) saline. Methods. Subjects exercised while they were wearing TPC in a heated room. Following an initial exercise period (bout 1), the subjects exited the room, removed the TPC, and for 20 minutes cooled passively at room temperature, received an infusion of cold normal saline, or were cooled by one of four devices (fan, forearm immersion in water, hand cooling, or water-perfused cooling vest). After cooling, the subjects donned the TPC and entered the heated room for another 50-minute exercise period (bout 2). Results. The subjects were not able to fully recover core temperature during a 20-minute rehabilitation period when provided rehydration and the opportunity to completely remove the TPC. Exercise durations were shorter during bout 2 when compared with bout 1 but did not differ by cooling intervention. The overall magnitudes and rates of cooling and heart rate recovery did not differ by intervention. Conclusions. No clear advantage was identified when active cooling devices and cold intravenous saline were compared with passive cooling in a moderate temperature after treadmill exercise in TPC.

The Relationship Between Shift Work, Sleep, and Cognition in Career Emergency Physicians

OBJECTIVES The 24-hour physician coverage of the emergency department (ED) requires shift work, which can result in desynchronosis and cognitive decline. We measured changes in cognition and sleep disturbance in attending emergency physicians (EPs) before and after day and overnight shifts. METHODS Thirteen EPs were tested before and after day and overnight shifts using the Paced Auditory Serial Addition Test (PASAT), the University of Southern California Repeatable Episodic Memory Test (REMT), the Trail Making Test (TMT), and the Stroop Color-Word Test. Sleep quality and fatigue were assessed using the Pittsburgh Sleep Quality Index (PSQI) and Chalder Fatigue Questionnaire (CFQ). Saliva samples were collected from each physician immediately before and after day shifts and night shifts for neurohormonal assays. RESULTS Significantly fewer words were recalled on the REMT after both day (-2.4, 95% confidence interval [CI] = -4.4 to -0.4) and overnight shifts (-4.6, 95% CI = -6.4 to -2.8). There was a significant postshift increase in words recalled from the last third of the REMT list after overnight shifts (6.6, 95% CI = 2.8 to 10.4). Sleep quality was worse in EPs (mean PSQI = 4.8, SD ± 2.5) compared to the normal population, with 31% of subjects reporting poor sleep quality. Postshift fatigue was correlated with the perceived difficulty of the shift. Salivary cortisol and melatonin demonstrated diurnal variation consistent with normal circadian rhythms. Morning cortisol peak was decreased or delayed in samples from physicians after a night shift. CONCLUSIONS These data indicate that short-term memory appears to decline after day and overnight shifts and confirms the high incidence of disturbed sleep in this population.

A Comparison of Cooling Techniques in Firefighters After a Live Burn Evolution

Abstract Objective. We compared the use of two active cooling devices with passive cooling in a moderate-temperature (≈22°C) environment on heart rate (HR) and core temperature (Tc) recovery when applied to firefighters following 20 minutes of fire suppression. Methods. Firefighters (23 men, two women) performed 20 minutes of fire suppression at a live-fire evolution. Immediately following the evolution, the subjects removed their thermal protective clothing and were randomized to receive forearm immersion (FI), ice water perfused cooling vest (CV), or passive (P) cooling in an air-conditioned medical trailer for 30 minutes. Heart rate and deep gastric temperature were monitored every 5 minutes during recovery. Results. A single 20-minute bout of fire suppression resulted in near-maximal mean ± standard deviation HR (175 ± 13 b·min−1, P; 172 ± 20 b·min−1, FI; 177 ± 12 b·min−1, CV) when compared with baseline (p < 0.001), a rapid and substantial rise in Tc (38.2° ± 0.7°, P; 38.3° ± 0.4°, FI; 38.3° ± 0.3°, CV) compared with baseline (p < 0.001), and body mass lost from sweating of nearly 1 kilogram. Cooling rates (°C·min) differed (p = 0.036) by device, with FI (0.05 ± 0.04) providing higher rates than P (0.03 ± 0.02) or CV (0.03 ± 0.04), although differences over 30 minutes were small and recovery of body temperature was incomplete in all groups. Conclusions. During 30 minutes of recovery following a 20-minute bout of fire suppression in a training academy setting, there is a slightly higher cooling rate for FI and no apparent benefit to CV when compared with P cooling in a moderate temperature environment.

Comparison of rehydration regimens for rehabilitation of firefighters performing heavy exercise in thermal protective clothing: a report from the fireground rehab evaluation (FIRE) trial.

Abstract Background. Performing fire suppression activities results in cardiovascular stress, hyperthermia, and hypohydration. Fireground rehabilitation (rehab) is recommended to blunt the deleterious effects of these conditions. Objective. We tested the hypothesis that three rehydration fluids provided after exercise while wearing thermal protective clothing (TPC) would produce different heart rate or core temperature responses during a second bout of exercise in TPC. Methods. On three occasions, 18 euhydrated firefighters (16 men, two women) wearing TPC completed a standardized, 50-minute bout of upper and lower body exercise in a hot room that mimicked the National Fire Protection Association (NFPA) rehabilitation guidelines of “two cylinders before rehab” (20 minutes of work, 10 minutes of recovery, 20 minutes of work). After an initial bout of exercise (bout 1), subjects were randomly assigned water, sport drink, or an intravenous (IV) infusion of normal saline equal to the amount of body mass lost during exercise. After rehydration, the subject performed a second bout of exercise (bout 2). Heart rates, core and skin temperatures, and exercise durations were compared with a two-way analysis of variance (ANOVA). Results. Subjects were firefighters with a mean (± standard deviation [SD]) age of 28.2 ± 11.3 years and a mean peak oxygen consumption (VO2peak) of 37.4 ± 3.4 mL/kg/min. The mean amount of fluid provided during the rehabilitation period was 527 ± 302 mL. No subject could complete either the pre- or postrehydration 50-minute bout of exercise. The mean (±SD) times to exhaustion were longer (p < 0.001) in bout 1 (25.9 ± 12.9 min, water; 28.0 ± 14.1 min, sport drink; 27.4 ± 13.8 min, IV) compared with bout 2 (15.6 ± 9.6 min, water; 14.7 ± 8.6 min, sport drink; 15.7 ± 8.0 min, IV) for all groups but did not differ by intervention. All subjects approached their age-predicted maximum heart rate at the end of bout 1 (180 ± 11 bpm) and bout 2 (176 ± 13 bpm). Core temperature rose 1.1°C ± 0.7°C during bout 1 and 0.5°C ± 0.4°C during bout 2. Core temperatures, heart rates, and exercise times during bout 2 did not differ between the rehydration fluids. Conclusions. Performances during a second bout of exercise in TPC did not differ when firefighters were rehydrated with water, sport drink, or IV normal saline when full rehydration was provided. Of concern was the inability of all subjects to complete two consecutive periods of heavy exercise in TPC, suggesting that the NFPAs “two cylinders before rehab” guideline may not be appropriate in continuous heavy work scenarios.

Effect of fatigue and hypohydration on gait characteristics during treadmill exercise in the heat while wearing firefighter thermal protective clothing

This study compared the gait characteristics of individuals walking in heat while wearing firefighting equipment in fatigued and non-fatigued states. Nineteen subjects performed a 50-min treadmill protocol in a heated room while gait patterns were recorded using a digital video camcorder. Forty gait cycles were analyzed near the beginning (9 min) and at the end (39-49 min) of exercise. Spatio-temporal gait variables including step frequency, step length, swing time, stance time, cycle time and double-support time were determined. Gait variability was quantified by the standard deviation (SD) and coefficient of variation (CV) of each variable. Left-right symmetry was calculated using the symmetry index (SI) and symmetry angle (SA). Paired t-tests (alpha = 0.05) were performed to identify difference between the beginning and the end of the protocol for each measured variable. Spatio-temporal gait characteristics did not differ between the beginning and the end of exercise. Gait variability of the double-support time increased at the end as measured by both SD (P = 0.037) and CV (P = 0.030) but no change was observed for other variables. Left-right symmetry measured using either SI or SA did not differ between sessions. In summary, spatio-temporal gait characteristics and symmetry while wearing firefighting equipment are insensitive to physiological fatigue. Prolonged walking in heat while wearing firefighting equipment may increase gait variability and therefore the likelihood of a fall. Future studies are needed to confirm the potential relationship between fatigue and gait variability and to investigate the possible influence of individual variation.

Estimating Core Temperature with External Devices After Exertional Heat Stress in Thermal Protective Clothing

ABSTRACT Background. Temperature measurement is important for emergency medical services (EMS) providers when identifying and treating heat illness or infection. Direct measures of body core temperature (Tc) are often expensive (ingestible capsules) or impractical (rectal probes) in the field. Multiple devices for estimating Tc have been adopted by EMS providers, with little understanding of the agreement between these devices and Tc. Objective. To examine the agreement between the results of five external thermometers and Tc after subjects experienced physical exertion while wearing protective clothing. Methods. Fifty firefighters completed treadmill walking in thermal protective clothing in a hot environment. Measurements of core, temporal, tympanic, forehead, and skin temperatures were obtained during a 20-minute recovery period simulating emergency incident rehabilitation. Results. The mean bias of external thermometers ranged from −1.31°C to −3.28°C when compared with Tc and exceeded the predetermined clinical cutoff of ±0.5°C from Tc. The 95% limits of agreement ranged from 2.75°C to 5.00°C. Conclusions. External measuring devices failed to accurately predict Tc in hyperthermic individuals following exertion. Confidence intervals around the bias were too large to allow for reasonable estimation of Tc. EMS providers should exercise caution when using any of these temperature estimation techniques.

Fitness Characteristics of a Suburban Special Weapons and Tactics Team

Pryor, RR, Colburn, D, Crill, MT, Hostler, DP, and Suyama, J. Fitness characteristics of a suburban special weapons and tactics team. J Strength Cond Res 26(3): 752–757, 2012—Special Weapons and Tactics (SWAT) operators are specialized law enforcement officers who traditionally perform their duties with higher anticipated workloads because of additional body armor, weapons, and equipment used for enhanced operations and protection. This elevated workload increases the need for SWAT operators to improve or maintain their physical fitness to consistently perform routine operations. Typical tasks require trunk rotation, overhead upper extremity use, upper and lower body strength use, and long waiting periods followed by explosive movements while wearing additional equipment. Eleven male SWAT operators from 1 SWAT team performed flexibility, strength, power, and aerobic capacity tests and a variety of job-related tasks. Data were compared with age- and gender-based normative data. Fitness testing revealed that officers ranked high on tests of muscular strength (leg strength, 90th percentile; bench press, 85th percentile); however, body composition (55th percentile), core body strength, and flexibility ranked lower. Furthermore, aerobic capacity and muscular power had a wide range of scores and were also not ideal to support maximal performance during routine operations. These data can assist exercise specialists choose fitness programs specifically for job-related tasks of SWAT operators when creating fitness programs. Fitness programming for law enforcement should focus on improving aerobic fitness, flexibility, core strength, and muscular power while maintaining muscular strength to meet the needs of these specialized officers.

A Randomized Controlled Trial of Aspirin and Exertional Heat Stress Activation of Platelets in Firefighters during Exertion in Thermal Protective Clothing

Abstract Purpose. Platelet aggregation is enhanced in firefighters following short bouts of work in thermal protective clothing (TPC). We sought to determine if aspirin therapy before and/or following exertion in TPC prevents platelet activation. Methods. In a double-blind, placebo-controlled study, 102 firefighters were randomized to receive daily therapy (81 mg aspirin or placebo) for 14 days before and a single dose (325 mg aspirin or placebo) following exercise in TPC resulting in four potential assignments: aspirin before and after exercise (AA), placebo before and after exercise (PP), aspirin before and placebo after exercise (AP), and placebo before and aspirin after exercise (PA). Platelet closure time (PCT) was measured with a platelet function analyzer before the 2-week treatment, after the 2 week treatment period, immediately after exercise, and 30, 60, and 90 minutes later. Results. Baseline PCT did not differ between groups. PCT changed over time in all four groups (p < 0.001) rising to a median of >300 seconds [IQR 99, 300] in AA and >300 [92, 300] in AP prior to exercise. Following exercise, median PCT decreased to in all groups. Median PCT returned to >300 seconds 30 minutes later in AA and AP and rose to 300 seconds in PA 60 minutes after exercise. Conclusions. Daily aspirin therapy blunts platelet activation during exertional heat stress and single-dose aspirin therapy following exertional heat stress reduces platelet activation within 60 minutes. Key words: firefighter; uncompensable heat stress; thermoregulation; emergency incident rehabilitation

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, andreduced work time. Victim extrication, the rescue-the-rescuer role of the rapid intervention team andrapid 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 andresult 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 andair-purifying respirator (PPE) andonce in shorts andt-shirt (CON). Oxygen consumption, vital signs, core andskin temperature, andperceptual measures of exertion, thermal sensation, andcomfort were monitored throughout the test. Results. Subjects achieved maximal oxygen consumption andmore than 90% of age-predicted maximum heart rate in both conditions. Heart rate, skin temperature, andmeasures of perceived exertion, comfort, andthermal sensation increased during the treadmill exercise but did not differ between the PPE andCON conditions. Core temperature increased in both the CON andPPE 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 andcotton 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.

Mitigation and Prevention of Exertional Heat Stress in Firefighters: A Review of Cooling Strategies for Structural Firefighting and Hazardous Materials Responders

Abstract Most duties performed by firefighters require the use of personal protective equipment, which inhibits normal thermoregulation during exertion, creating an uncompensable heat stress. Structured rest periods are required to correct the effects of uncompensable heat stress and ensure that firefighter safety is maintained and that operations can be continued until their conclusion. While considerable work has been done to optimize firefighter cooling during fireground operations, there is little consensus on when or how cooling should be deployed. A systematic review of cooling techniques and practices among firefighters and hazardous materials operators was conducted to describe the state of the science and provide recommendations for deploying resources for fireground rehab (i.e., structured rest periods during an incident). Five electronic databases were searched using a selected combination of key words. One hundred forty publications were found in the initial search, with 27 meeting all the inclusion criteria. Two independent reviewers performed a qualitative assessment of each article based on nine specific questions. From the selected literature, the efficacy of multiple cooling strategies was compared during exertion and immediately following exertion under varying environmental conditions. When considering the literature available for cooling firefighters and hazardous materials technicians during emergency incident rehabilitation, widespread use of cooling devices does not appear to be warranted if ambient temperature and humidity approximate room temperature and protective garments can be removed. When emergency incident rehabilitation must be conducted in hot or humid conditions, active cooling devices are needed. Hand/forearm immersion is likely the best modality for cooling during rehab under hot, humid conditions; however, this therapy has a number of limitations. Cooling during work thus far has been limited primarily to cooling vests and liquid- or air-cooled suits. In general, liquid-perfused suits appear to be superior to air-cooled garments, but both add weight to the firefighter, making current iterations less desirable. There is still considerable work to be done to determine the optimal cooling strategies for firefighters and hazardous materials operators during work. Key words: fireground; emergency incident rehabilitation; hyperthermia; hazmat