A comparison of cooling techniques in firefighters after a live [613735]

A comparison of cooling techniques in firefighters after a live
burn evolution
Deanna Colburn, MPT1, Joe Suyama, MD2, Steven E Reis, MD2,3, Julia L Morley2, Fredric L
Goss, PhD1, Yi-Fan Chen4, Charity G Moore, PhD4, and David Hostler, PhD2
1)Center for Exercise and Health-Fitness Research, Department of Health and Physical Activity,
University of Pittsburgh
2)Emergency Responder Human Performance Lab, Department of Emergency Medicine,
University of Pittsburgh
3)Cardiovascular Institute, University of Pittsburgh
4)Center for Research of Health Care Data Center
Abstract
Objective— We compared two active cooling devices to passive cooling in a moderate ( ≈22°C)
temperature environment on heart rate (HR) and core temperature (T c) recovery when applied to
firefighters following 20 min. of fire suppression.
Methods— Firefighters (23 male, 2 female) 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 five minutes during recovery.
Results— A single 20-minute bout of fire suppression resulted in near maximal HR (175±13 – P,
172±20 – FI, 177±12 beats•min−1 – CV) when compared to baseline (p < 0.001), a rapid and
substantial rise in T c (38.2±0.7 – P, 38.3±0.4 – FI, 38.3±0.3° – CV) compared to baseline (p <
0.001), and mass lost from sweating of nearly one 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 min. 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 to P cooling in a moderate temperature environment.
Keywords
Heat stress; hyperthermia; thermoregulation; firefighter
Address Correspondence to: David Hostler, PhD Emergency Responder Human Performance Lab Department of Emergency
Medicine University of Pittsburgh 3600 Forbes Ave Pittsburgh PA 15261 [anonimizat] 412-647-4113 (phone) 412-647-6999
(fax).
The contents of this manuscript are solely the responsibility of the authors and do not necessarily represent the official view of FEMA,
NCRR, or NIH.
Conflict of Interest The authors have no conflicts of interest related to this topic.
NIH Public Access
Author Manuscript
Prehosp Emerg Care . Author manuscript; available in PMC 2012 April 1.
Published in final edited form as:
Prehosp Emerg Care . 2011 ; 15(2): 226±232. doi:10.3109/10903127.2010.545482.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript

INTRODUCTION
Work in a hot environment, experienced during fire suppression, results in activation of heat
loss mechanisms without changing the hypothalamic set point for T c [1]. The typical human
response to rising T c is to convectively move excess heat from the core to the periphery by
increasing skin blood flow. The rising skin temperature is subsequently accompanied by
sweating releasing heat to the environment by evaporation.
Structural fire suppression encompasses multiple functions including fire extinguishment,
victim rescue, ventilation of smoke, and post-fire overhaul that require heavy physical
exertion [2,3]. Firefighters must use thermal protective clothing (TPC) during these fire
suppression activities to protect them from extreme environmental heat, trauma, and burn
injuries [4]. However, these garments inhibit normal thermoregulation resulting in
cardiovascular and thermal strain [4]. Although skin blood flow is increased and sweating
commences during work in TPC, evaporation is largely eliminated leading to a progressive
increase in T c and HR and a decrease in plasma volume. The resultant heat and
cardiovascular stress limits work capacity and may cause injury to the firefighter.
To improve safety at a fire scene following exertion in TPC, structured rehabilitation periods
including heat stress remediation are mandated by the National Fire Protection Association
(NFPA) Standard 1584 [5]. However, there are few specific recommendations for cooling
found within that guideline.
There have been multiple studies of active and passive cooling for exercise induced
hyperthermia in both athletes and firefighters [6–9]. Multiple devices including cooling
vests, hand and forearm immersion in cold water, and misting fans have been investigated
after subjects exercised while wearing TPC in a controlled laboratory setting or non-fire
field settings [8–12].
A previous laboratory study of firefighters working in TPC has shown that active cooling by
forearm and hand immersion improved heart rate (HR) and body core temperature (T c)
recovery during structured breaks and extended work time in a hot, humid environment
when compared to passive cooling and misting fans [9]. However, these findings have not
been verified in the field nor has an active cooling modality been compared to passive
cooling in a controlled, moderate temperature and humidity environment, such as could be
created in an air-conditioned vehicle. The objective of the present study was to compare the
effect of a liquid perfused cooling vest (CV), forearm immersion (FI), and passive cooling in
a moderate temperature environment (P) on HR and T c recovery following 20 minutes of
structural fire suppression activity.
METHODS
The University of Pittsburgh Institutional Review Board approved this study. Subjects
provided written informed consent prior to participation. Subjects consisted of 25
firefighters (23 males, 2 females) who were apparently healthy adults age 32.1 ± 7.6 years
(Table 1). Subjects were recruited from both career and volunteer fire departments in
response to a regional advertisement and were certified to the Pennsylvania Essentials of
Firefighting with Live Burn or the NFPA 1001 Standard for Professional Firefighter
Qualifications Firefighter I or Firefighter II [13].
Preliminary Testing
Subjects received a physical exam from a study physician including a 12-lead ECG and
maximal exercise test prior to the fire evolution. Height and weight were determined using aColburn et al. Page 2
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Healthometer Digital Scale and stadiometer. Body fat was determined by three skinfold
measurements [14]. Exclusion criteria included known cardiac or respiratory disease, use of
medications known to alter HR response or thermoregulation, and previous abdominal
surgery. No subject was excluded after screening.
Subjects completed a Bruce protocol treadmill test during the screening visit to determine
aerobic capacity (VO 2max). Open circuit spirometry (Parvomedics TrueOne 2400, Sandy
UT) was used to measure respiratory rate (RR), volume of expired air (VE STPD ), oxygen
consumption (VO 2) and carbon dioxide production (VCO 2). A 12-lead ECG and blood
pressure (BP) was obtained at rest and every three minutes during the protocol, immediately
post exercise, and every five minutes during recovery for 15 minutes to screen for
undiagnosed ischemic response to exercise. Stress test results were interpreted by a
cardiologist. Female subjects were screened for pregnancy prior to the treadmill test and live
fire evolutions.
Testing Session
Live fire evolutions took place on two consecutive days in July 2009 at the Allegheny
County Fire Academy between 0900 and 1500 hrs. Nine of 25 subjects participated on both
days. These subjects used a different cooling device on each day. Subjects were asked to
refrain from caffeine, alcohol, and exercise for 12 hours prior to participation. Subjects were
asked to eat their normal breakfast on the day of the fire evolution and were provided an
indigestible pill to monitor T c (HQ Inc, Palmetto FL). Subjects were instructed to take the
capsule eight hours prior to arrival. After arriving, the subjects voided, had urine specific
gravity checked to confirm euhydration (USG < 1.020), were weighed nude, and were fitted
with a Polar HR monitor (Woodbury NY).
Following instrumentation, subjects participated in a NFPA 1403 compliant live fire
evolution supervised by Fire Academy instructors [15]. The training evolution lasted
approximately 20 minutes and required subjects, in teams of four, to advance a 4.4 cm
charged hose line to the second floor of a concrete structure to extinguish and ventilate a
simulated bedroom fire. Subjects rotated position on the hose line and advanced to the next
room to repeat the process. Instructors reignited the extinguished rooms to allow continuous
extinguishment and ventilation until 20 minutes had elapsed. Subjects then withdrew from
the structure where exit HR and T c were assessed. Subjects then received an assignment to a
cooling strategy.
Firefighters wore standard uniform pants and long sleeve t-shirt. Each firefighter brought
their own TPC ensemble consisting of heavy coat, trousers, gloves, steel toed boots,
polycarbonate helmet, Nomex hood, and self-contained breathing apparatus (SCBA). All
TPC was inspected by Fire Academy instructors on the day of the fire evolution to ensure
compliance with NFPA 1971 standards [16].
After completing the fire suppression activities, participants were randomized to one of the
following three cooling groups for rehabilitation: forearm and hand immersion in cool water
using a specially designed folding chair (FI) (N = 11), (Kore Kooler™, Morning Pride,
Dayton OH), a liquid perfused cooling vest (CV) (N = 13) (Cool Shirt® Personal Cooling
System, Shafer Enterprises, Inc., Stockbridge GA), or passive cooling in an air-conditioned
(22.2 ± 0.6°C) medical trailer (P) (N = 9). The rehabilitation period lasted 30 minutes during
which all subjects consumed exactly 500 ml of room temperature water. Subjects
randomized to FI or CV were seated in a shaded, open-air pavilion (22.5 ± 2.9°C, relative
humidity 47.2 ± 11.0%). The cooling vest was applied following manufacture's instructions
using ice water in the reservoir and wetting the vest in ice water prior to use. The forearmColburn et al. Page 3
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immersion chair reservoirs were filled with water (20.9 ± 0.4°C) collected from a fire hose
before each subject use.
After randomization, subjects doffed SCBA, helmet, gloves, coat, and Nomex hood and
opened the front of the TPC trousers. Subjects were seated during the intervention and data
collection. During the 30-minute post-fire monitoring period T c, and HR were recorded
every five minutes. Oral temperature (SureTemp 690, Welch Allyn, Skaneateles Falls NY)
was recorded at the beginning and end of the 30-minute period.
Following data collection, subjects were weighed nude prior to voiding. Body mass was
corrected for the oral intake of water to provide an estimate of body water lost from
sweating.
Statistical Analysis
Data were entered from paper recording forms into a spreadsheet, verified for accuracy, and
imported into SPSS for Mac v11 (SPSS Inc, Chicago IL) and SAS version 9.2 for analyses.
All subject demographic and morphometric measurements were continuous and are
presented as mean ± SD. Heart rate, T c, and change in body mass measured pre/post fire
suppression were compared by two-way ANOVA conditioned on time and cooling strategy.
HR and T c were measured on each individual after fire suppression every five minutes from
0 to 30 minutes. We used a repeated measures marginal model assuming a normal
distribution with first-order autoregressive covariance structures for both HR and T c. We
first tested for group differences in the linear and curvature changes over time ( α=0.05 for
each interaction). If the interaction was not significant, we dropped the term from the model
and tested the next highest ordered term. Predicted equations from the final models for HR
recovery and cooling rate are presented for each group over time. Oral and core
temperatures at the beginning and end of the rehab period were examined with a Pearson
Correlation Coefficient and Bland-Altman Test of Agreement. All statistical tests were two
sided and conducted at α=0.05.
A post hoc analysis was performed for T c and HR using commonly applied physiological
cut-offs to determine if a firefighter may return to the incident. Survival analysis stratified
by cooling device was performed for the criteria 1) HR < 100 beats•min−1, 2) HR < 80
beats•min−1, and 3) 50% recovery of the rise in T c during fire suppression. In exploratory
analyses, HR recovery was also stratified by firefighter VO 2max using cutoffs previously
identified for the fire service (1: low fit, below 42 (N=15), 2: moderately fit, 42–48 (N=8),
and 3: high fit, above 48 mL•kg−1•min−1 (N=9)) [2].
RESULTS
Physiologic measures after fire suppression
As expected, twenty minutes of fire suppression activities results in significant
cardiovascular and thermal stress. Heart rate approached age predicted maximum values (p
< 0.001) while T c increased approximately 0.7°C in all groups (p < 0.001) (Table 2).
Participants in the three groups had similar HR, T c, and changes in these measures after fire
suppression activities. Subjects lost 0.84 ± 0.34 (P), 0.72 ± 0.41 (FI), 0.86 ± 0.36 (CV) kg of
mass following fire suppression.
Physiologic measures during recovery
Heart rate decreased over time during the recovery period (linear slope, p < 0.001) with a
leveling off after 20 minutes (time2 p<0.0001) (Figure 1). Heart rate recovery did not differ
among groups (difference in slopes test, p = 0.85).Colburn et al. Page 4
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Cooling rates (°C•min−1) were 0.03±0.02 (P), 0.05±0.04 (FI), and 0.03±0.04 CV and
differed by group (p=0.036) with the FI demonstrating a greater cooling rate over time
(Figure 1).
Oral temperature at the start and end of the rehab was correlated with T c (R2 = 0.31, p <
0.001). However, a Bland-Altman analysis revealed that agreement was poor with a mean
bias of −1.3°C (95%CI −2.7, 0.05) indicating that oral temperature collected in the field
does not accurately predict T c.
Survival Analysis of HR and T c recovery
Survival analysis of HR recovery was conditioned on the commonly accepted criterion of
HR less than 100 beats•min−1 before returning to fire suppression activities and a more
conservative criterion of HR less than 80 beats•min−1. When examined by cooling device,
the survival curves did not differ between groups (Figure 2A, 2C). A substantial proportion
of subjects in all groups failed to reach the recovery criterion of less than 80 beats•min−1
during a 30-minute rest interval following fire suppression. Two subjects (1, P; 1 CV) failed
to reach the recovery criterion of less than 100 beats•min−1 during a 30-minute rest interval
following fire suppression. These exploratory analyses were repeated dividing subjects by
aerobic capacity into three groups using previously published guidelines for firefighter
fitness of 42.0 and 48.0 mL•kg−1•min−1 VO 2max (Figure 2B, 2D) (9). When examined by
fitness, the moderately fit group achieved HR < 100 beats•min−1 more slowly than both the
low and high fit groups (p = 0.03). This difference was not observed for the HR < 80 bpm
criterion.
Survival analyses of T c were performed using the relative criterion of 50% recovery of the
rise observed during fire suppression (Figure 3). No differences were identified between
cooling strategies.
DISCUSSION
This study compared two common active cooling modalities to passive cooling in moderate
temperature and humidity environment following 20 minutes of fire suppression. Our study
is similar to previous studies of fire suppression in that we observed a significant
hyperthermia, tachycardia, and hypohydration [17,18]. Although the forearm immersion
group had a more rapid cooling rate, recovery was incomplete in all groups when firefighters
were provided an operationally relevant interval of 30 minutes for fireground rehabilitation.
Our study augments what is currently known about cooling firefighters during fireground
rehabilitation by examining firefighter cooling in moderate ambient temperature ( ≈22°C).
Three previous studies examining recovery in a hot environment have reported that it is
difficult to mitigate heat stress without active cooling devices such as fans, vests, or forearm
immersion [9,10,19]. However, across much of North America and Europe, extremely hot
(≥35°C) ambient temperatures are rare. In a previous study of active and passive cooling,
conducted in our lab, we failed to identify an advantage of active cooling during a 20-minute
recovery period after 50 minutes of treadmill walking in TPC in a heated room [8]. In that
laboratory study, the cooling rates for all modalities averaged 0.05°C•min−1 which is similar
to what we have reported in the FI group in the present field study. We believe these small
differences in P and CV cooling rates between the laboratory and the field can be attributed
to the garments worn during the recovery period. In the laboratory study, subjects recovered
in long uniform pants and a short sleeve cotton shirt without wearing TPC. In this field
study, subjects recovered in TPC pants (a common field practice) and a long sleeve cotton
shirt (a fire academy requirement). Long sleeve shirts are not normally worn in the summer
months outside of the training academy and TPC could be pushed down below the kneesColburn et al. Page 5
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while the firefighter is seated for recovery, which may negate the small advantage seen in
the FI group.
Another study comparing hand cooling in cold tap water failed to result in differences in T c
and HR recovery when compared to the control condition of seated recovery in a cooler
15°C room after removing the helmet, coat and hood [11]. Collectively, these studies
indicate that the addition of cooling devices does not allow for full recovery of HR and T c in
an operationally relevant time interval when the majority of thermal protective clothing is
removed and subjects rest in a moderate temperature and humidity environment.
Furthermore, our data show that an air-conditioned vehicle may be used in a field setting to
create this advantageous environment when the temperature and/or humidity are suboptimal.
Our study contrasts with a study of multimodal cooling (forearm immersion combined with
a cooling vest) in a 21°C room after 20 minutes of treadmill walking where passive cooling
was found to be inferior to active cooling [20]. However, in that laboratory study, the
recovery period was limited to 15 minutes and appears to include the time required for
doffing and donning TPC for a second bout of treadmill walking. We note that the cooling
rate for the active cooling arm in is comparable to the passive cooling group in the present
report (0.03 ± 0.02°C/min vs. 0.02 ± 0.01°C/min) [20]. The passive cooling rate of −0.01 ±
0.01°C/min reported in that study [20] is likely influenced by the short period of continued
heat accumulation following cessation of exercise in protective clothing that has been
reported in other studies [8,18,21]. Although the multimodal technique of CV and FI takes
advantage of a larger surface area for cooling and may be advantageous for short recovery
periods, we hypothesize greater T c reduction would have been noted in the passive cooling
group in Barr et al if the recovery period had been lengthened beyond 15 minutes.
It is important to note that even after 30 minutes of structured recovery that included cooling
and rehydration, most subjects remained mildly hyperthermic with seated HR exceeding 80
bpm. It may not be possible to return a firefighter to baseline or near-baseline status within a
20–30 minute recovery period after significant exertion in TPC using current cooling
strategies. Prolonged fireground operations may need to be facilitated by increasing the
number of personnel available for operations to allow for longer or more frequent recovery
periods. It may also be necessary to investigate additional cooling devices and work
practices to prevent or attenuate heat stress during fire suppression activities.
Although not powered for this purpose, the exploratory survival analysis of HR and T c
recovery is provocative and requires further investigation. Survival analysis was used to
describe the proportion of the cohort not achieving a desired level of physiologic recovery in
the allotted 30-minute rehab period. No differences in several commonly used criteria for
HR or T c recovery were seen between devices. This strengthens the observation that creating
a cool, low humidity environment that favors thermoregulation is as effective as applying a
cooling device.
However, differences in HR recovery were noted when stratified by fitness. A previous
study of fire suppression skills found that the most demanding operations required a VO 2 of
at least 42 mL•kg−1•min−1 [2]. While this criterion is often used as a minimum standard for
firefighter fitness, sustaining those activities for an operationally relevant interval of 10
minutes requires a VO 2max of approximately 48 mL•kg−1•min−1. When stratifying subjects
by VO 2max we observed slower HR recovery in the middle fit (42–48 mL•kg−1•min−1)
group when compared to the low and high fit groups. The difference between the middle and
high fit groups is consistent with previous studies showing faster reestablishment of cardiac
vagal tone and greater HR recovery immediately following exercise [22,23]. The lack of
difference between the low and high fit groups is more difficult to reconcile. We speculateColburn et al. Page 6
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that the low fit individuals either self-paced during the fire suppression activities, working at
a lower percentage of their individual VO 2max and relying more heavily on their partners, or
were simply unable to achieve higher HR. Since we were not able to record HR during fire
suppression we cannot verify this in the present report. However, if these observations are
confirmed in a larger cohort, it may indicate that employing the 42 mL•kg−1•min−1
minimum for firefighter fitness leads to the deployment of firefighters who will have
difficulty recovering for subsequent bouts of work, especially if those subsequent work
periods require heavy exertion such as victim rescue [3]. Furthermore, validation of these
observations may require reconsideration of how individuals are monitored and the decision
making process to return them to fire suppression activities.
Our subjects performed fire suppression and ventilation. However, this was a training fire in
a controlled setting. Physiologic responses in the uncertain and rapidly changing
environment of an actual fire may differ. Nevertheless, our protocol produced near maximal
HR, a rapid and substantial rise in T c, and nearly one liter of mass lost to sweating in an
operationally relevant time interval. Furthermore, our subject pool was diverse representing
both the career and volunteer fire service and displayed a wide range of fitness and
morphometrics but they may not be representative of firefighters in other areas of North
America and Europe.
We compared an air-conditioned environment to two popular cooling devices on a typical
early-summer day in Western Pennsylvania (approximately 24°C). We cannot address the
effectiveness of other devices. However, given that the currently marketed devices employ a
common and limited set of conductive or convective cooling strategies, we believe that it is
unlikely that dramatically different results would be obtained with another cooling device
applied after fire suppression. Finally, while these data suggest there is a limited role for
active cooling of firefighters when moderate temperature environment and low humidity
conditions favor passive cooling, we cannot speak to their use in environmental conditions
other than those presently employed in this study and in studies of recovery in hot, humid
conditions [9].
In conclusion, a single 20-minute bout of fire suppression in a training academy setting
results in near maximal HR, a rapid and substantial rise in T c, and mass lost from sweating
of nearly one kilogram. Although the cooling rate (°C•min−1) was slightly higher in the FI
group, removing TPC in a moderate temperature environment (approximately 22°C) after
fire suppression results in 30-minute HR and T c recovery that is similar to the recovery
realized with forearm immersion or ice water-perfused cooling vests.
Acknowledgments
The authors gratefully acknowledge the support of the Allegheny County Fire Academy, Pittsburgh Fire Fighters
Local No. 1, Pittsburgh Bureau of Fire, and UPMC Prehospital Care. Special thanks to Chief Robert Full, Academy
Director Al Wickline, and Staff Instructor Steve Imbarlina. Finally, we thank our subjects for their participation and
dedication to the fire service. The results of this study do not imply endorsement by the American College of Sports
Medicine.
This study was funded by the FEMA Assistance to Firefighters Grant Program (EMW-2006-FP-02245). This study
was also supported in part by Grant Number UL1 RR024153 from the National Center for Research Resources
(NCRR), a component of the National Institutes of Health (NIH), and NIH Roadmap for Medical Research.
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Figure 1.
Heart rate and T c recovery during a 30-minute rehab period following fire suppression for
passive (solid line), forearm immersion (dashed line) and liquid perfused vest (dotted line)
cooling.
The predicted equations for the HR recovery by device are VEST: Predicted heart rate =
139.07 − 4.543 * Minute + 0.091 * Minute2, CHAIR: Predicted heart rate = 127.90 − 4.543
* Minute + 0.091 * Minute2, PASSIVE: Predicted heart rate = 132.68 − 4.543 * Minute +
0.091 * Minute2
The predicted equations for the T c by device are VEST: Predicted T c = 38.463 − 0.023 *
Minute, CHAIR: Predicted T c = 38.804 − 0.048 * Minute, PASSIVE: Predicted T c = 38.427
− 0.021 * Minute.Colburn et al. Page 9
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Figure 2.
Survival analysis of HR recovery during a 30-minute rehab period following fire
suppression for the criterion of HR < 100 and HR < 80 stratified by cooling device (Panels
A, C) and subjects aerobic fitness (Panels B, D).Colburn et al. Page 10
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Figure 3.
Survival analysis of T c recovery during a 30-minute rehab period following fire suppression
stratified by cooling device.Colburn et al. Page 11
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NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptColburn et al. Page 12
Table 1
Subject Demographics
Passive ( N = 9) Forearm Immersion ( N = 13) Cooling Vest ( N = 11)
Age (years) 31.2 ± 8.9 32.2 ± 7.2 30.6 ± 6.4
Height (cm) 174.4 ± 5.7 175.2 ± 7.3 176.9 ± 6.5
Weight (kg) 89.3 ± 22.4 86.6 ± 15.6 95.7 ± 22.2
VO 2peak (mg/kg per min) 43.3 ± 8.9 43.3 ± 9.0 40.4 ± 8.1
Body Fat (%) 18.4 ± 7.2 14.9 ± 3.9 17.6 ± 6.8
Values presented as mean ± standard deviation.
Prehosp Emerg Care . Author manuscript; available in PMC 2012 April 1.

NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptColburn et al. Page 13Table 2
Physiologic measures before and immediately following 20 minutes of fire suppression
Heart Rate (bpm) Core Temperature (°C) Change in Body Mass (kg)
Pre Post Pre Post
Passive 121 ± 29 175 ± 13 37.5 ± 0.5 38.2 ± 0.7 −0.84 ± 0.34
Forearm Immersion 108 ± 23 172 ± 20 37.4 ± 0.3 38.3 ± 0.4 −0.72 ± 0.41
Cooling Vest 116 ± 22 177 ± 12 37.6 ± 0.2 38.3 ± 0.3 −0.86 ± 0.36
Values presented as mean ± standard deviation. bpm = beats per minute. Heart rate and T c increased following 20 minutes of fire suppression in all groups (p < 0.001). No differences were identified
between groups in post HR, T c, or change in body mass.
Prehosp Emerg Care . Author manuscript; available in PMC 2012 April 1.