The impact of fire suppression tasks on firefighter hydration: A critical review with consideration of the utility of reported hydration measures

BACKGROUND: Firefighting is a highly stressful occupation with unique physical challenges, apparel and environments that increase the potential for dehydration. Dehydration leaves the firefighter at risk of harm to their health, safety and performance. The purpose of this review was to critically analyse the current literature investigating the impact of fighting ‘live’ fires on firefighter hydration. METHODS: A systematic search was performed of four electronic databases for relevant published studies investigating the impact of live fire suppression on firefighter hydration. Study eligibility was assessed using strict inclusion and exclusion criteria. The included studies were critically appraised using the Downs and Black protocol and graded according to the Kennelly grading system. RESULTS: Ten studies met the eligibility criteria for this review. The average score for methodological quality was 55 %, ranging from 50 % (‘fair’ quality) to 61 % (‘good’ quality) with a ‘substantial agreement’ between raters (k = .772). Wildfire suppression was considered in five studies and structural fire suppression in five studies. Results varied across the studies, reflecting variations in outcome measures, hydration protocols and interventions. Three studies reported significant indicators of dehydration resulting from structural fire suppression, while two studies found mixed results, with some measures indicating dehydration and other measures an unchanged hydration status. Three studies found non-significant changes in hydration resulting from wildfire firefighting and two studies found significant improvements in markers of hydration. Ad libitum fluid intake was a common factor across the studies finding no, or less severe, dehydration. CONCLUSIONS: The evidence confirms that structural and wildfire firefighting can cause dehydration. Ad libitum drinking may be sufficient to maintain hydration in many wildfire environments but possibly not during intense, longer duration, hot structural fire operations. Future high quality research better quantifying the effects of these influences on the degree of dehydration is required to inform policies and procedures that ensure firefighter health and safety

Diagnostic accuracy of calculated serum osmolarity to predict dehydration in older people: adding value to pathology lab reports

Objectives: To assess which osmolarity equation best predicts directly measured serum/plasma osmolality and whether its use could add value to routine blood test results through screening for dehydration in older people. Design: Diagnostic accuracy study Participants: Older people (≥65 years) in 5 cohorts: Dietary Strategies for Healthy Ageing in Europe (NU-AGE, living in the community), Dehydration Recognition In our Elders (DRIE, living in residential care), Fortes (admitted to acute medical care), Sjöstrand (emergency room) or Pfortmueller cohorts (hospitalised with liver cirrhosis). Reference standard for hydration status: Directly measured serum/plasma osmolality: current dehydration (serum osmolality >300mOsm/kg), impending/current dehydration (≥295mOsm/kg). Index tests: 39 osmolarity equations calculated using serum indices from the same blood draw as directly measured osmolality. Results: Across five cohorts 595 older people were included, of whom 19% were dehydrated (directly measured osmolality >300mOsm/kg). Of 39 osmolarity equations, five showed reasonable agreement with directly measured osmolality and three had good predictive accuracy in subgroups with diabetes and poor renal function. Two equations were characterized by narrower limits of agreement, low levels of differential bias and good diagnostic accuracy in ROC plots (areas under the curve >0.8). The best equation was osmolarity =1.86 × (Na+ + K+) + 1.15 × glucose + urea + 14 (all measured in mmol/L). It appeared useful in people aged ≥65 years with and without diabetes, poor renal function, dehydration, in men and women, with a range of ages, health, cognitive and functional status. Conclusions: Some commonly used osmolarity equations work poorly, and should not be used. Given costs and prevalence of dehydration in older people we suggest use of the best formula by pathology laboratories using a cutpoint of 295mOsm/L (sensitivity 85%, specificity 59%), to report dehydration risk opportunistically when serum glucose, urea and electrolytes are measured for other reasons in older adults

New method for photoresist stripping

Vacuum dehydration of negatively working photoresist eliminates trace contamination of conventional stripping methods. The semiconductor substrate is coated with photoresist, exposed, developed, cured, and etched, and then placed in a vacuum. Following dehydration, the resist film is removable with ordinary solvents

Dehydration mechanism of a small molecular solid: 5-nitrouracil hydrate

Previous studies of the dehydration of 5-nitrouracil (5NU) have resulted in it being classified as a ‘‘channel hydrate’’ in which dehydration proceeds principally by the exit of the water molecules along channels in the structure. We have re-examined this proposal and found that in fact there are no continuous channels in the 5NU structure that would contribute to such a mechanism. Product water molecules would be immediately trapped in unlinked voids in the crystal structure and would require some additional mechanism to break loose from the crystal. Through a detailed structural analysis of the macro and micro structure of the 5NU as it dehydrates, we have developed a model for the dehydration process based on the observed development of structural defects in the 5NU crystal and the basic crystallography of the material. The model was tested against standard kinetic measurements and found to present a satisfactory account of kinetic observations, thus defining the mechanism. Overall, the study shows the necessity of complementing standard kinetic studies with a parallel macro and micro examination of the dehydrating material when evaluating the mechanisms of dehydration and decomposition processes

Controlled Rate Thermal Analysis and Differential Scanning Calorimetry of Sepiolites and Palygorskites

A series of sepiolites, palygorskites and "Rocky Mountain Leather" clay minerals have been analysed by controlled rate thermal analysis and differential scanning calorimetry. Eight weight loss steps are observed and are structure and composition dependent. Three dehydration steps and five dehydroxylation steps are observed. The mass spectrometric curve mimicked the differential thermogravimetric (DTGA) curve enabling the detailed determination of the dehydration and dehydroxylation step

Cryopreservation of Byrsonima intermedia embryos followed by room temperature thawing

Byrsonima intermedia is a shrub from the Brazilian Cerrado with medicinal properties. The storage of biological material at ultra-low temperatures (-196°C) is termed cryopreservation and represents a promising technique for preserving plant diversity. Thawing is a crucial step that follows cryopreservation. The aim of this work was to cryopreserve B. intermedia zygotic embryos and subsequently thaw them at room temperature in a solution rich in sucrose. The embryos were decontaminated and desiccated in a laminar airflow hood for 0-4 hours prior to plunging into liquid nitrogen. The embryo moisture content (% MC) during dehydration was assessed. Cryopreserved embryos were thawed in a solution rich in sucrose at room temperature, inoculated in a germination medium and maintained in a growth chamber. After 30 days, the embryo germination was evaluated. No significant differences were observed between the different embryo dehydration times, where they were dehydrated for at least one hour. Embryos with a MC between 34.3 and 20.3% were germinated after cryopreservation. In the absence of dehydration, all embryos died following cryopreservation. We conclude that B. intermedia zygotic embryos can be successfully cryopreserved and thawed at room temperature after at least one hour of dehydration in a laminar airflow bench

Climate change and the kidney

The worldwide increase in temperature has resulted in a marked increase in heat waves (heat extremes) that carries a markedly increased risk for morbidity and mortality. The kidney has a unique role not only in protecting the host from heat and dehydration but also is an important site of heat-associated disease. Here we review the potential impact of global warming and heat extremes on kidney diseases. High temperatures can result in increased core temperatures, dehydration, and blood hyperosmolality. Heatstroke (both clinical and subclinical whole-body hyperthermia) may have a major role in causing both acute kidney disease, leading to increased risk of acute kidney injury from rhabdomyolysis, or heat-induced inflammatory injury to the kidney. Recurrent heat and dehydration can result in chronic kidney disease (CKD) in animals and theoretically plays a role in epidemics of CKD developing in hot regions of the world where workers are exposed to extreme heat. Heat stress and dehydration also has a role in kidney stone formation, and poor hydration habits may increase the risk for recurrent urinary tract infections. The resultant social and economic consequences include disability and loss of productivity and employment. Given the rise in world temperatures, there is a major need to better understand how heat stress can induce kidney disease, how best to provide adequate hydration, and ways to reduce the negative effects of chronic heat exposure.Published versio

Short-term heat acclimation is effective and may be enhanced rather than impaired by dehydration

Most heat acclimation data are from regimes longer than 1 week, and acclimation advice is to prevent dehydration. Objectives: We hypothesized that (i) short-term (5-day) heat acclimation would substantially improve physiological strain and exercise tolerance under heat stress, and (ii) dehydration would provide a thermally independent stimulus for adaptation. Methods: Nine aerobically fit males heat acclimated using controlled-hyperthermia (rectal temperature 38.5°C) for 90 min on 5 days; once euhydrated (EUH) and once dehydrated (DEH) during acclimation bouts. Exercising heat stress tests (HSTs) were completed before and after acclimations (90-min cycling in T a 35°C, 60% RH). Results: During acclimation bouts, [aldosterone] plasma rose more across DEH than EUH (95%CI for difference between regimes: 40-411 pg ml -1 ; P=0.03; n=5) and was positively related to plasma volume expansion (r=0.65; P=0.05), which tended to be larger in DEH (CI: -1 to 10%; P=0.06; n=9). In HSTs, resting forearm perfusion increased more in DEH (by 5.9 ml 100 tissue ml -1 min -1 : -11.5 to -1.0; P=0.04) and end-exercise cardiac frequency fell to a greater extent (by 11 b min -1 : -1 to 22; P=0.05). Hydration-related effects on other endocrine, cardiovascular, and psychophysical responses to HSTs were unclear. Rectal temperature was unchanged at rest but was 0.3°C lower at end exercise (P < 0.01; interaction: P=0.52). Conclusions: Short-term (5-day) heat acclimation induced effective adaptations, some of which were more pronounced after fluid-regulatory strain from permissive dehydration, and not attributable to dehydration effects on body temperature. Am. J. Hum. Biol. 26:311-320, 2014. © 2014 Wiley Periodicals, Inc

Numerical method for solving multipoints elliptic-parabolic equation for dehydration process

Drying is the oldest and efficient form of preserving fruits. This research focuses on the mathematical modeling of tropical fruits dehydration using instant controlled pressure drop (Détente Instantanée Controlée or known as DIC) technique. We proposed a modification of mathematical modeling to enhance the previous modeling from Haddad et al. [10]. The mathematical modeling presents the dehydration process of DIC technique which involves parameters such as pressure, water content, time dependency, dimension of region and temperature behavior. The modification of the mathematical modeling has been done by transforming the quadratic equation to partial differential equation (PDE). The simulation of the dehydration process will be illustrated through Jacobi method based on two, three and five points forward difference schemes. The sequential algorithm is developed by using Matlab 7.6.0 (R2008a) programming. The numerical analysis of finite difference schemes in terms of number of iteration, time execution, maximum error and computational cost are compared

Dehydration in the TTL estimated from the water vapor match

The match method is applied to the quantification of the dehydration process in the tropical tropopause layer (TTL) over the western Pacific. The match pairs are sought from the Soundings of Ozone and Water in the Equatorial Region (SOWER) campaign network observations with the use of isentropic trajectories. For those pairs identified, extensive screening procedures are performed to verify the representativeness of the air parcel and the validity of the isentropic treatment and to check possible water injection by deep convection, consistency between the sonde data and analysis field, and conservation of the ozone content. Among those pairs remaining, we found some cases corresponding to the first quantitative value of dehydration associated with horizontal advection in the TTL. The statistical features on the dehydration for the air parcels advected in the lower TTL are derived from the match pairs. Match analysis indicates that ice nucleation starts before the relative humidity with respect to ice (RHice) reaches the value of 207 ± 81% (1σ) and that the air mass is dehydrated until the RHice reaches 83 ± 30% (1σ). The efficiency of dehydration is estimated as the relaxation time of the relative humidity for the supersaturated air parcel to approach the saturation state. This is empirically estimated from the match pairs as the quantity that reproduces the second water vapor observation given the first observed water vapor amount and the sequence of the saturation mixing ratio of the match air mass exposed during the advection. The relaxation time is found to range from 2 to 3 hours, which agrees with those reported from previous studies