Jacob P. DeBlois

Quantifying Dehydration in the Fire Service Using Field Methods and Novel Devices

Abstract Objective. This study reports measurements of hydration status among firefighters prior to training, documents changes in hydration status after prolonged firefighting training, and reports the utility of salivary measurements to assess changes in hydration in field environments. Methods. Nude body mass measurements as well as urinary and salivary measurements of hydration status were taken before and after approximately three hours of firefighting training activities. Initial hydration status was assessed via urinary and salivary measures. Changes in body mass and total body water were measured following firefighting activity and correlated with changes in urinary and salivary measures of hydration. Results. The most important findings of this study were that a high percentage of firefighters arrived at training in a significantly or seriously dehydrated state; that firefighters lost a significant amount of body mass because of firefighting operations; and that portable salivary osmolality measurements showed much stronger correlation with changes in hydration status after firefighting operations than standard urinary measurements did. Conclusions. Firefighters arriving in a dehydrated state are at risk for heat injuries and may be in a physically and/or psychologically compromised state at the outset of firefighter training. Even during cool autumn days with ample fluids available, firefighters experience dehydration during typical firefighting activities, so the ability to measure hydration status throughout such activities may be important. Our data suggest that quantification of changes in hydration status through salivary osmolality measurements may provide a viable field measurement tool for such activities.

Cardiovascular Strain of Firefighting and the Risk of Sudden Cardiac Events.

Approximately 45% to 50% of line-of-duty deaths in the fire service are caused by sudden cardiac deaths, which most often occur during or shortly after firefighting duties. We present a theoretical model linking the cardiac, vascular, and hematological responses of firefighting to the triggering of sudden cardiac death in susceptible individuals.

Use of salivary osmolality to assess dehydration.

Abstract Objective. To investigate the ability of salivary osmolality to assess dehydration while subjects perform alternating work/rest cycles in personal protective equipment (PPE). Methods. Eight healthy men (mean ± standard deviation age: 23.5 ± 4.9 years; body fat: 17.8% ± 5.0%; maximum volume of oxygen consumption [VO2max]: 57.2 ± 5.5 mL·kg−1·min−1) performed two exercise trials: one while wearing shorts and a T-shirt (EX) and one while wearing firefighting PPE (EX+PPE). Saliva samples were taken before exercise, at minutes 40, 80, and 120 of the exercise trial, and during recovery. Results. Percent body mass loss (BML) was significantly greater while the subjects were wearing PPE (2.18% ± 0.54% vs. control 0.81% ± 0.30%). Salivary osmolality increased significantly in both trials (73.4 ± 12.4 to 125.1 ± 30.3 mOsm·kg−1 and 70.1 ± 12.5 to 83.6 ± 17.7 mOsm·kg−1); however, the increase in the EX+PPE trial was significantly greater than the increase in the EX trial. Plasma osmolality did not change significantly in either trial, whereas urinary osmolality increased significantly in both trials. Changes in salivary osmolality were strongly correlated with percent BML (r = 0.80; p < 0.01). Conclusion. Salivary osmolality may be a sensitive indicator of moderate dehydration under carefully controlled conditions. Key words: exercise; heat; dehydration; osmolality; saliva; personal protective equipment