Postconcussive Symptoms Over the First 14 Days After Mild Traumatic Brain Injury: An Experience Sampling Study.

OBJECTIVE: This study examined changes in postconcussive symptoms (PCS) over the acute postinjury recovery period, focusing on how daily PCSs differ between mild traumatic brain injury (mTBI) and other injury types. SETTING: An urban emergency department (ED) in Western Pennsylvania. SUBJECTS: A total of 108 adult patients with trauma being discharged from the ED were recruited and grouped by injury type: mild TBI (mTBI; n = 39), head injury without mTBI (HI: n = 16), and non-head-injured trauma controls (TCs: n = 53). MAIN MEASURES: Subjects completed a baseline assessment and an experience sampling method (ESM) protocol for 14 consecutive days postinjury: outcomes were daily reports of headaches, anxiety, and concentration difficulties. RESULTS: Controlling for confounders, multilevel modeling revealed greater odds of headache and concentration difficulties on day 1 postinjury among the HI and mTBI groups (vs TCs). These odds decreased over time, with greater reductions for the HI and mTBI groups compared with TCs. By day 14, there were no group differences in PCS. In addition, only the HI group reported higher initial levels of anxiety and a steeper slope relative to TCs. CONCLUSION: Patients with HI, regardless of whether they meet the American Congress of Rehabilitation Medicines definition of mTBI, have higher odds of typical PCS immediately postinjury, but faster rates of recovery than TCs. ESM can improve understanding the dynamic nature of postinjury PCS.

Validation of the OMNI Scale of Thermal Sensations.

Concurrent and construct validation of the OMNI Scale of Thermal Sensations was examined in a sample of 16 adult men and 5 adult women. Concurrent validity was established by regressing OMNI ratings of thermal sensation against core and skin temperatures obtained during treadmill walking while wearing firefighter thermal-protective clothing in temperatures between 33 and 35 degrees C. Construct validity was established by regressing the OMNI scale against a construct-specific visual analogue scale. OMNI scale responses accounted for statistically significant variance in both skin temperature and core temperature (48% and 51%, respectively) and visual analogue scale responses (84%). Concurrent and construct validity were established for the OMNI Scale of Thermal Sensations in healthy adults performing treadmill walking while wearing fire fighter thermal protective clothing.

The effect of shift length on fatigue and cognitive performance in air medical providers.

OBJECTIVE: To employ a battery of previously validated surveys and neuropsychological tests to compare changes in fatigue and cognitive abilities of air medical providers after 12- and 24-hour shifts. METHODS: A convenience sample of 34 flight nurses and flight paramedics employed by one air medical service completed the Pittsburgh Sleep Quality Index (PSQI) and the Chalder Fatigue Questionnaire (CFQ) to determine fatigue before and after 12-hour (n = 16) and 24-hour (n = 19) shifts. A battery of neuropsychological tests, including the University of Southern California Repeatable Episodic Memory Test (USC-REMT), Paced Auditory Serial Addition Test (PASAT), Trail Making Test (TMT), and Stroop Color-Word Test were administered before and after the shift to measure changes in cognition. We compared the change in scores stratified by shift length using t-tests, Wilcoxon signed-rank test, and Fisher's exact test. RESULTS: Participants in the 12- and 24-hour shift groups were aged 36 ± 8 years (12-hour shifts) and 39 ± 6 years (24-hour shifts) (mean ± standard deviation) and were preponderantly male (62% 12-hour shifts; 63%, 24 hour shifts). The PSQI scores identified 50% of both 12-hour and 24-hour shift subjects as having poor sleep quality. Preshift fatigue was described as a median 2/10 (interquartile range [IQR] = 2-4) and fatigue declined by the end of the shift to a median 1/10 [IQR = 1-2], p = 0.006. Providers averaged 6.8 hours of sleep during 24-hour shifts and 1 hour of sleep during 12-hour shifts. Changes in cognitive scores did not differ between groups. CONCLUSIONS: This study identified no changes in cognitive performance following 12- and 24-hour shifts in air medical providers. This suggests that 24-hour shifts in an air medical service with low to moderate utilization do not have a detrimental effect on cognition as measured by this test battery, and are comparable to 12-hour shifts in terms of impact on cognitive function.

Estimating core temperature with external devices after exertional heat stress in thermal protective clothing.

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 (T(c)) are often expensive (ingestible capsules) or impractical (rectal probes) in the field. Multiple devices for estimating T(c) have been adopted by EMS providers, with little understanding of the agreement between these devices and T(c). OBJECTIVE: To examine the agreement between the results of five external thermometers and T(c) 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 T(c) and exceeded the predetermined clinical cutoff of ±0.5°C from T(c). The 95% limits of agreement ranged from 2.75°C to 5.00°C. CONCLUSIONS: External measuring devices failed to accurately predict T(c) in hyperthermic individuals following exertion. Confidence intervals around the bias were too large to allow for reasonable estimation of T(c). EMS providers should exercise caution when using any of these temperature estimation techniques.

Cognitive function following treadmill exercise in thermal protective clothing.

Occupational injuries are common among firefighters who perform strenuous physical exertion in extreme heat. The thermal protective clothing (TPC) worn by firefighters inhibits normal thermoregulation, placing the firefighter at risk of hypohydration and hyperthermia that may result in cognitive decline. We tested whether cognitive function changes after treadmill exercise in TPC. In an initial study (Cog 1), ten healthy volunteers performed up to 50 min of treadmill exercise while wearing TPC in a heated room. A battery of neurocognitive tests evaluating short-term memory, sustained and divided attention, and reaction time was administered immediately before and after exercise. In a follow-up study (Cog 2), 19 healthy volunteers performed a similar exercise protocol with the battery of cognitive tests administered pre-exercise, immediately post-exercise, and serially up to 120 min after exercise. Subjects performed 46.4 ± 4.6 and 48.1 ± 3.6 min of exercise in the Cog 1 and Cog 2, respectively. In both studies heart rate approached age predicted maximum, body mass was reduced 1.0-1.5 kg, and body core temperature increased to levels similar to what is seen after fire suppression. Neurocognitive test scores did not change immediately after exercise. Recall on a memory test was reduced 60 and 120 min after exercise. The mean of the 10 slowest reaction times increased in the 120 min after exercise. Fifty minutes of treadmill exercise in TPC resulted in near maximal physiologic strain but alterations in neurocognitive performance were not noted until an hour or more following exercise in TPC.

A comparison of cooling techniques in firefighters after a live burn evolution.

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 (T(c)) 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 T(c) (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.

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 (VO(2peak)) 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 degrees C +/- 0.7 degrees C during bout 1 and 0.5 degrees C +/- 0.4 degrees 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 NFPA's "two cylinders before rehab" guideline may not be appropriate in continuous heavy work scenarios.