Validity, Reliability, and Inertia of Four Different Temperature Capsule Systems.

PURPOSE: Telemetric temperature capsule systems are wireless, relatively noninvasive, and easily applicable in field conditions and have therefore great advantages for monitoring core body temperature. However, the accuracy and responsiveness of available capsule systems have not been compared previously. Therefore, the aim of this study was to examine the validity, reliability, and inertia characteristics of four ingestible temperature capsule systems (i.e., CorTemp, e-Celsius, myTemp, and VitalSense). METHODS: Ten temperature capsules were examined for each system in a temperature-controlled water bath during three trials. The water bath temperature gradually increased from 33°C to 44°C in trials 1 and 2 to assess the validity and reliability, and from 36°C to 42°C in trial 3 to assess the inertia characteristics of the temperature capsules. RESULTS: A systematic difference between capsule and water bath temperature was found for CorTemp (0.077°C ± 0.040°C), e-Celsius (-0.081°C ± 0.055°C), myTemp (-0.003°C ± 0.006°C), and VitalSense (-0.017°C ± 0.023°C; P < 0.010), with the lowest bias for the myTemp system (P < 0.001). A systematic difference was found between trial 1 and trial 2 for CorTemp (0.017°C ± 0.083°C; P = 0.030) and e-Celsius (-0.007°C ± 0.033°C; P = 0.019), whereas temperature values of myTemp (0.001°C ± 0.008°C) and VitalSense (0.002°C ± 0.014°C) did not differ (P > 0.05). Comparable inertia characteristics were found for CorTemp (25 ± 4 s), e-Celsius (21 ± 13 s), and myTemp (19 ± 2 s), whereas the VitalSense system responded more slowly (39 ± 6 s) to changes in water bath temperature (P < 0.001). CONCLUSIONS: Although differences in temperature and inertia were observed between capsule systems, an excellent validity, test-retest reliability, and inertia was found for each system between 36°C and 44°C after removal of outliers.

Fluid replacement advice during work in fully encapsulated impermeable chemical protective suits.

A major concern for responders to hazardous materials (HazMat) incidents is the heat strain that is caused by fully encapsulated impermeable chemical protective suits. In a research project, funded by the US Department of Defense, the thermal strain experienced when wearing these suits was studied. One particular area of interest was the fluid loss of responders during work in these suits as dehydration may be an additional health concern to the heat strain. 17 City of Raleigh firemen and 24 students were tested at two different labs. Subjects between the ages of 25 and 51 were used for human subject trials in a protocol approved by the local ethical committee. Six different Level A HazMat suits were evaluated in three climates: moderate (24°C, 50% RH, 20°C WBGT), warm-wet (32°C, 60% RH, 30°C WBGT), and hot-dry (45°C, 20% RH, 37°C WBGT, 200 W/m2 radiant load) and at three walking speeds: 2.5 km/hr, 4 km/hr, and 5.5 km/hr. 4 km/hr was tested in all three climates and the other two walking speeds were tested in the moderate climate. Weight loss data was collected to determine fluid loss during these experiments. Working time ranged from as low as 20 min in the hot-dry condition to 60 min (the maximum) in the moderate climate, especially common at the lowest walking speed. The overall results from all experiments showed that fluid loss ranged from 0.2-2.2 L during these exposures, with the average fluid loss being 0.8 L, with 56% of the data between 0.5 L and 1 L of fluid loss. Further analysis showed that a suggestion of drinking 0.7 Liter per hour would safely hydrate over 50% of responders after one work-rest cycle. Applying this fluid volume over three work-rest cycles only put 11% of responders at risk of hypohydration vs. the 57% at risk with no fluid intake.

The effect of a helmet on cognitive performance is, at worst, marginal: a controlled laboratory study.

The present study looked at the effect of a helmet on cognitive performance under demanding conditions, so that small effects would become more detectible. Nineteen participants underwent 30 min of continuous visual vigilance, tracking, and auditory vigilance (VTT + AVT), while seated in a warm environment (27.2 (±0.6) °C, humidity 41 (±1)%, and 0.5 (±0.1) m s(-1) wind speed). The participants wore a helmet in one session and no helmet in the other, in random order. Comfort and temperature perception were measured at the end of each session. Helmet-wearing was associated with reduced comfort (p = 0.001) and increased temperature perception (p < 0.001), compared to not wearing a helmet. Just one out of nine cognitive parameters showed a significant effect of helmet-wearing (p = .032), disappearing in a post-hoc comparison. These results resolve previous disparate studies to suggest that, although helmets can be uncomfortable, any effect of wearing a helmet on cognitive performance is at worst marginal.

The effect of two sock fabrics on perception and physiological parameters associated with blister incidence: a field study.

The goal of the present study was to investigate differences in perception and skin hydration at the foot of two sock fabrics with distinct moisture properties in a realistic military setting. Thirty-seven military recruits wore two different socks (PP: 99.6% polypropylene and 0.4% elastane, and BLEND: 50% Merino-wool, 33% polypropylene, and 17% polyamide), one on each foot. Measurements were carried out after a daily 6.5-km march on 4 days. Each participant rated temperature, dampness, friction, and comfort for each foot. On a daily selection of participants, skin hydration was measured on three sites of both feet using a corneometer, and moisture content of the socks was determined. BLEND was rated to be cooler, less damp, and more comfortable (P < 0.05). Two out of three skin sites were drier for BLEND than PP (P < 0.05). Moreover, BLEND stored 2.9 ± 0.3 times more moisture compared to PP. Thus, under the present conditions, socks such as BLEND are to be preferred over polypropylene socks.

Thermal perception of ventilation changes in full-face motorcycle helmets: subject and manikin study.

We report the effects of full-face motorcycle helmet ventilation systems on heat, airflow, noise, and comfort perception for ventilation changes on the scalp. Eight subjects (aged 28.0 ± 5.4 years) underwent two experimental trials at ambient temperatures of 23.7 ± 0.4 °C or 27.5 ± 0.3 °C. In each trial, the thermally equilibrated subjects underwent two examination phases, during which four different helmets were assessed at wind speeds of 39.2 ± 1.9 km h(-1) and 59.3 ± 1.4 km h(-1). Vent-induced heat loss in the scalp ranged from -6.1 to 6.1 W, corresponding to vents being closed or opened, respectively. Perception of vent-induced changes was assessed immediately after the change. We find that the vent-induced heat loss, the subject, and the helmet are the most important response factors. In addition, comparison of two helmets with similar vent-induced heat loss suggests that internal airflow patterns may be important in explaining the observed perception differences.

The effect of pre-cooling intensity on cooling efficiency and exercise performance.

Although pre-cooling is known to enhance exercise performance, the optimal cooling intensity is unknown. We hypothesized that mild cooling opposed to strong cooling circumvents skin vasoconstriction and thermogenesis, and thus improves cooling efficiency reflected in improved time to exhaustion. Eight males undertook three randomized trials, consisting of a pre-cooling and an exercise session. During the pre-cooling, performed in a room of 24.6 +/- 0.4 degrees C and 24 +/- 6% relative humidity, participants received either 45 min of mild cooling using an evaporative cooling shirt or strong cooling using an ice-vest. A no-cooling condition was added as a control. Subsequent cycling exercise was performed at 65%[Vdot]O(2peak) in a climatic chamber of 29.3 +/- 0.2 degrees C and 80 +/- 3% relative humidity. During the pre-cooling session, mild and strong cooling decreased the skin blood flow compared with the control. However, no differences were observed between mild and strong cooling. No thermogenesis was observed in any conditions investigated. The reduction of body heat content after pre-cooling was two times larger with strong cooling (39.5 +/- 8.4 W . m(-2)) than mild cooling (21.2 +/- 5.1 W . m(-2)). This resulted in the greatest improvement in time to exhaustion with strong cooling. We conclude that the cooling intensities investigated had a similar effect on cooling efficiency (vasoconstriction and thermogenesis) and that the improved performance after strong cooling is attributable to the greater decrease in body heat content.

The effect of rowing headgear on forced convective heat loss and radiant heat gain on a thermal manikin headform.

Both radiant and forced convective heat flow were measured for a prototype rowing headgear and white and black cotton caps. The measurements were performed on a thermal manikin headform at a wind speed of 4.0 m . s(-1) (s = 0.1) in a climate chamber at 22.0 degrees C (s = 0.05), with and without radiant heat flow from a heat lamp, coming from either directly above (90 degrees ) or from above at an angle of 55 degrees . The effects of hair were studied by repeating selected measurements with a wig. All headgear reduced the radiant heat gain compared with the nude headform: about 80% for the caps and 95% for the prototype rowing headgear (P < 0.01). Forced convective heat loss was reduced more by the caps (36%) than by the prototype rowing headgear (9%) (P < 0.01). The radiant heat gain contributed maximally 13% to the net heat transfer, with or without headgear, showing that forced convective heat loss is the dominant heat transfer parameter under the chosen conditions. The results of the headgear - wig combinations were qualitatively similar, with lower absolute heat transfer.