Physiological and psychological responses in Fire Instructors to heat exposures

AimFire Service Instructors (FSI) are exposed to many repeated periods of high environmental temperatures when training firefighters. Such repeated exposures will impose significant strains on the function of instructors. We aimed to measure the effects of a training programme including repeated exposures to heat, termed “Wears” in the fire service, on the physiological, psychological some immunological markers of Fire Service Instructors.MethodsSix FSI and six physiologically matched controls completed blood and cardiovascular tests pre and post a 4 wk heat instruction training block, controls completed the tests only. FSI were given a 7 wk period of no heat exposure prior to starting the training. Physiological and perceptual measures were taken pre and post the first and last Wear of the 4 wk training protocol.ResultsThere were acute effects of a Wear on core temperature and physiological strain index, as well as measures of fatigue. The acute exposure to heat during a Wear led to a consistent decrease in CRP (−10% to −40%), increased IL6 concentrations 33–45%) as well as increased RPE and TSS. Over the training programme significantly lower quantities of white cells, particularly neutrophils, leukocytes and monocytes were found in the FSI group. Between the start and the end of the 4 week training programme the FSI showed a significantly greater physiological strain index (PSI) to the Wears, which nearly doubled from 2.5 to 4.7 (p<0.05).ConclusionPhysiological and psychological measures indicate that FSI may be experiencing symptoms and changes to their health consistent with an overtraining type condition.     

Strategies to combat heat strain during and after firefighting

The use of phase change cool vests during firefighting and the efficacy of 20 min cold water hand immersion following such activity was investigated. Core temperature was unaffected by cool vest wear, as was skin temperature, sweat rate and heart rate, and cannot be recommended for use. There was a trend for core temperature decline to be accelerated by hand immersion after 10 min, but this trend disappeared after 20 min. Hand immersion had no substantive effect on core temperature attenuation in firefighters who had partially removed their clothing, consumed cold water and sat in a cool and ventilated room.     

A non-invasive device to continuously determine heat strain in humans

Heat stroke remains a very dangerous, potentially lethal illness in humans. The Physiological Strain Index (PSI), originally based on heart rate and rectal temperature recordings in humans, describes heat strain in quantitative terms. The objective of our study was to establish whether the rectal temperature recordings serving to determine the PSI could be replaced by a non-invasive skin temperature sensor combined with a heat flux sensor (Double Sensor) attached to the inside of a helmet. We assumed (i) that the difference between the recordings by the device under test and the rectal temperature should be less than ±1.0 °C for ±2 S.D. at 10, 25, and 40 °C ambient temperature, and (ii) that the temperature predictions based on the Double Sensor temperature should differ by less than 1 PSI score from the calculations based on recordings of the rectal temperature. Twenty male subjects participated in the study. Rectal, nasopharyngeal, and skin temperatures, heat flux, and cardiovascular data were collected continuously during different experimental setups at ambient temperatures of 10, 25, and 40 °C. Depending on the protocols, the exercise intensities varied from 25% to 55% of the individual VO_2max. A comparison of the recordings obtained from the device under test with those of the rectal temperature revealed that (i) the recordings of the Double Sensor differed by −0.16 to 0.1 °C from the mean rectal temperature, (ii) the concordance correlation coefficients (CCC) during all work and rest periods rose with rising ambient temperatures (all work periods: 10 °C: 0.49; 25 °C: 0.69; 40 °C: 0.75; all rest periods: 10 °C: 0.39; 25 °C: 0.81; 40 °C: 0.74), and that (iii) the Double Sensor in the helmet showed that during all rest periods and in all ambient conditions, the temperature dropped much more quickly than what was recorded when taking the rectal temperature (p<0.01). When we compared the PSI values based on the rectal temperature recordings to those determined by the Double Sensor, it was found that (i) the PSI based on the Double Sensor recordings differed by −0.27 to 0.17 from the mean PSI established by rectal temperature recordings. Furthermore, the CCC for the PSI rose during all work periods (10 °C: 0.81, 25 °C: 0.93, 40 °C: 0.87) and rest periods (10 °C: 0.68; 25 °C: 0.93; 40 °C: 0.79). In conclusion, under warm/hot environmental conditions the device under test provided a reliable method of assessing the PSI in operational environments to improve physiological situational awareness and safety in action. However, there are some limitations that reduce the device's performance in cold environments; these need to be investigated further.     

Repeated thermal conditioning during the neonatal period affects behavioral and physiological responses to acute heat stress in chicks

ObjectiveThe aim of the present study was to investigate the effects of repeated thermal conditioning (RTC) at an early age on physiological and behavioral responses in chicks.MethodsBirds were assigned to one of the four treatments in which the RTC was exposure to 40 °C for 15 min daily. The treatments were 1) no thermal conditioning (control); 2) early exposure group (EE; RTC from 2 to 4 days of age); 3) later exposure group (LE; RTC from 5 to 7 days of age); or 4) both early and later exposure (BE; RTC from 2 to 7 days of age). All groups of chicks were challenged with high ambient temperature (40 °C for 15 min) at two weeks of age.ResultsDuring heat challenge, initiation times of dissipation behaviors (panting and wing-drooping) were measured. Rectal temperature and respiration rate were measured after and before heat challenge. Hypothalamic samples and blood were collected at the end of heat challenges. Initiation times of dissipation behaviors and rectal temperature were not affected by the treatments. Increases in respiration rate in response to heat challenge were suppressed by early RTC treatment. There was no clear pattern of glucose levels in relation to thermal conditioning, whereas plasma corticosterone levels were decreased by early treatment (EE and BE groups). Hypothalamic thyrotropin releasing hormone gene expression was suppressed by early and later thermal conditioning and suppressed further by both early and later exposure. Neuropeptide Y gene expression in the BE group was lower than in the other groups, with a similar trend for corticotropin releasing hormone expression.ConclusionOur results suggest that the effect of repeated thermal conditioning on the central thermoregulatory system depends on the number of times that chicks experienced conditioning. In addition, repeated thermal conditioning has greater effects on the acquisition of thermotolerance when conditioning occurs in chicks of two to four days of age in comparison with chicks of five to seven days of age.     

Parabrachial Interleukin-6 Reduces Body Weight and Food Intake and Increases Thermogenesis to Regulate Energy Metabolism

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The right to exit and skilled labour emigration: Ethical considerations for compulsory health service programmes

Compulsory (health) service contracts have recently received considerable attention in the normative literature. The service contracts are considered and offered as a permissible and liberal alternative to emigration restrictions if individuals relinquish their right to exit via contract in exchange for the state‐funded tertiary education. To that end, the recent normative literature on the service programmes has particularly focused on discussing the circumstances or conditions in which the contracts should be signed, so that they are morally binding on the part of the skilled workers. However, little attention is devoted to the relevance of the right to exit for the debate on compulsory service programmes. In this paper, I argue that even if the service contracts are voluntary, and thus the would‐be medical students voluntarily relinquish their right to exit, the reasons behind the right should be taken into account for the contracts to be morally valid. A clear understanding of the right to exit is a must in order not to breach its basic components and for the service contracts to be morally binding. To that end, I provide two accounts of the reasons to value the right to exit by presenting Patti Lenard's discussion of the right to exit and by reconstructing James Griffin's account of human rights. I conclude by offering brief ethical considerations for compulsory health service programmes grounded in the reasons to value the right to exit.