Testing the effectiveness of techniques for reducing heat strain in Royal Navy nuclear, biological and chemical cleansing stations' teams.

Nine personnel simulating the work of an NBC cleansing station (CS) in conditions expected in Middle Eastern waters had a limited work duration due to incapacitating heat strain. When the subjects were allowed five minutes rest periods after every 10 minutes of work, the endurance of seven of the subjects was limited to between 75-105 minutes due to heat strain and heat illness. By the point of withdrawal mean (SD) rectal temperature (Tre) had risen by 1.8 degrees C (0.4 degree C). The other two subjects were withdrawn earlier because they reached cardiac safety limits. When the hands were immersed (HI) in 10 degrees C water during the five minute rest periods heat strain was significantly lower (P < 0.01) and work endurance times were increased. One subject was withdrawn early on reaching cardiac safety limits, two on reaching Tre limits (39 degrees C) at 105 minutes, and six subjects completed the 180 minute exposure with a final Tre of 38.4 degrees C (0.3 degree C). Using 'iced' (0 degree C) rather than 10 degrees C water for HI further reduced heat strain (P < 0.01) and increased endurance times. Three subjects were withdrawn early on reaching cardiac safety limits, the remaining six completing the 180 minute exposure, with a final Tre of 38.3 degrees C (0.5 degree C). Using an ice-vest (IV) in conjunction with HI further reduced heat strain (P < 0.01) and increased endurance times. Two subjects were withdrawn early on reaching cardiac safety limits, the remaining seven completing the 180 minute exposure, with a final Tre of 38.2 degrees C (0.8 degree C) when 10 degrees C HI water was used, and Tre 38.0 degrees C (0.4 degree C) when 0 degree C HI water was used. There were no reports of finger numbness or loss of dexterity due to HI, and all personnel were able to remove their own individual Protective Equipment (IPE) without difficulty. It is expected that using HI will not reduce the ability to decontaminate or undress others. The HI technique and IV equipment should be introduced into the Fleet. 'Iced' water should be used in preference to 10 degrees C, although any water colder than 25 degrees C will provide some benefit. The IVs increased torso girth and personnel should try them on (with frozen ice packs inserted) prior to their use and ensure that their protective clothing still fits, or obtain a larger size.