W. Jon Williams

Effects of fire fighter protective ensembles on mobility and performance

Many studies have shown that fire fighter turnout gear and equipment may restrict mobility. The restriction of movement is usually due to a decrease in range of motion (ROM). It is important to know how much the decrease in ROM affects performance. The aim of this study was to determine the effects of fire fighter protective ensembles on mobility and performance by measuring static and dynamic range of motion (ROM) and job-related tasks. Eight healthy adults (5 males, 3 females), aged 20-40 years, participated in this study. The study consisted of measuring a battery of motions and fire fighter specific tasks while wearing a standard fire fighter ensemble (SE) or regular light clothing (baseline or BL). Several BL ROM tests were significantly (p < 0.05) different from the SE test, including a decrease in shoulder flexion, cervical rotation and flexion, trunk lateral flexion, and stand and reach. There was a significant decrease in time from SE to baseline performing the one-arm search task and object lift. These overall findings support the need for a comprehensive ergonomic evaluation of protective clothing systems to ascertain human factors issues. The development of a Standard Ergonomics Test Practice for further use in laboratories that conduct personal protective systems evaluations using human test subjects is recommended.

Measurement accuracy of heart rate and respiratory rate during graded exercise and sustained exercise in the heat using the Zephyr BioHarness.

The Zephyr BioHarness was tested to determine the accuracy of heart rate (HR) and respiratory rate (RR) measurements during 2 exercise protocols in conjunction with either a laboratory metabolic cart (Vmax) or a previously validated portable metabolic system (K4b2). In one protocol, HR and RR were measured using the BioHarness and Vmax during a graded exercise up to V˙O2max (n=12). In another protocol, HR and RR were measured using the BH and K4b2 during sustained exercise (30% and 50% V˙O2max for 20 min each) in a hot environment (30 °C, 50% relative humidity) (n=6). During the graded exercise, HR but not RR, obtained from the BioHarness was higher compared to the Vmax at baseline and 30% V˙O2max (p<0.05), but showed no significant difference at other stages with high correlation coefficients for both HR (r=0.87-0.96) and RR (r=0.90-0.99 above 30% V˙O2max). During the exercise in the heat, there were no significant differences between the BioHarness and K4b2 system. Correlation coefficients between the methods were low for HR but moderately to highly correlated (0.49-0.99) for RR. In conclusion, the BioHarness is comparable to Vmax and K4b2 over a wide range of V˙O2 during graded exercise and sustained exercise in the heat.

Effects of Liquid Cooling Garments on Recovery and Performance Time in Individuals Performing Strenuous Work Wearing a Firefighter Ensemble

This study investigated the effects of body cooling using liquid cooling garments (LCG) on performance time (PT) and recovery in individuals wearing a fully equipped prototype firefighter ensemble (PFE) incorporating a self-contained breathing apparatus (SCBA). Six healthy male participants (three firefighters and three non-firefighters) completed six experimental sessions in an environmental chamber (35°C, 50% relative humidity), consisting of three stages of 15 min exercise at 75% VO2max, and 10 min rest following each exercise stage. During each session, one of the following six conditions was administered in a randomized order: control (no cooling, CON); air ventilation of exhaust SCBA gases rerouted into the PFE (AV); top cooling garment (TCG); TCG combined with AV (TCG+AV); a shortened whole body cooling garment (SCG), and SCG combined with AV (SCG+AV). Results showed that total PT completed was longer under SCG and SCG+AV compared with CON, AV, TCG, and TCG+AV (p < 0.01). Magnitude of core temperature (Tc) elevation was significantly decreased when SCG was utilized (p < 0.01), and heart rate recovery rate (10 min) was enhanced under SCG, SCG+AV, TCG, and TCG+AV compared with CON (p < 0.05). Estimated Esw rate (kg·h−1) was the greatest in CON, 1.62 (0.37), and the least in SCG+AV 0.98 (0.44): (descending order: CON > AV > TCG = TCG+AV > SCG > SCG+AV) without a statistical difference between the conditions (p < 0.05). Results of the present study suggest that the application of LCG underneath the PFE significantly improves the recovery during a short period of rest and prolongs performance time in subsequent bouts of exercise. LCG also appears to be an effective method for body cooling that promotes heat dissipation during uncompensable heat stress.

Surgical mask placement over N95 filtering facepiece respirators: Physiological effects on healthcare workers

Background and objective:  Filtering facepiece respirators (‘N95 Masks’) may be in short supply during large‐scale infectious outbreaks. Suggestions have been made to extend their useful life by using a surgical mask as an outer barrier, but the physiological impact of this added barrier upon the wearer has not been studied.

Physiological Monitoring in Firefighter Ensembles: Wearable Plethysmographic Sensor Vest versus Standard Equipment

We evaluated the accuracy of a wearable sensor vest for real-time monitoring of physiological responses to treadmill exercise. Ten subjects in standard firefighter ensembles, treadmill exercising at 50% VO2 max, had heart rate (HR), respiratory rate (RR), skin temperature (Tsk), oxygen saturation (SaO2), tidal volume (VT), and minute ventilation ([Vdot]E) recorded concurrently by a wearable plethysmographic sensor vest and standard laboratory physiological monitoring equipment for comparison. A high degree of correlation was noted for most of the measured variables [HR (r = 0.99), RR (r = 0.98), Tsk (r = 0.98), [Vdot]E (r = 0.88), and SaO2 (r = 0.79)]. VT (r = 0.60) had a moderate correlation, although a paired differences analysis showed a mean paired difference of –0.03 L. This mean paired difference represents a 1.92% variation for VT. Data from the wearable sensor vest is comparable to data captured from standard laboratory physiological monitoring equipment on subjects wearing standard firefighter ensembles while exercising at a moderate work rate. This study demonstrates the accuracy of the wearable sensor technology for these physiological parameters under these conditions and suggests that it could be useful for actual field studies of firefighters in traditional firefighting gear.

Field evaluation of a new prototype self-contained breathing apparatus.

Firefighters are required to use a self-contained breathing apparatus (SCBA) for respiratory protection when engaged in a variety of firefighting duties. While the SCBA provides crucial respiratory support and protection, it is also cumbersome and heavy, thus adding to the physical work performed by the firefighter. The purpose of the present study was to evaluate and compare the low profile SCBA prototype to a standard SCBA, as assessed by the objective and subjective measures of mobility and comfort, time of donning/doffing, as well as by acquiring user feedback on SCBA design features during field activities. The results of the present study indicated that the prototype SCBA was rated as a significant improvement over the standard SCBA in the areas of range of motion (ROM), mobility, comfort, induction of fatigue, interaction with protective clothing, and operability when worn over a standard firefighter ensemble, while performing a series of International Association of Fire Fighters Fire Ground Survival Program training exercises. Statement of Relevance: A prototype SCBA was evaluated and compared with a standard SCBA, focusing on the objective and subjective measures of mobility and comfort during field activities. Feedback from end users was collected during the evaluation. The findings of the present study can be used for improving the system design and overall performance of new prototype SCBAs.

Behavioral and Technological Adaptation

Maintaining a euhydrated state is critical for normal biochemical and physiological function. Hydration is normally a dynamic process of the constant loss of water from the body (insensible as well as dynamic water loss from sweating) being replaced through drinking, eating, and the metabolism of food. Significant water loss from sweating during exercise must be replaced to avoid heat and other related injuries. Monitoring of physiological processes has occurred from ancient times but has become sophisticated in the last 100 years. Wearable wireless monitoring has been developed allowing the wearer to determine their physiological status under a variety of conditions (exercise, environmental). Monitoring may help avoid injury that may occur when physiological limits are exceeded (e.g., heat stroke). In addition to physiological monitoring, wearable cooling technologies have been developed which limit the effects of environment on the physiological burden of the environment reducing the risk of heat injury to workers.

Using Trunk Posture to Monitor Heat Strain at Work

Abstract This study aimed to determine if trunk posture during walking is related to increases in rectal temperature (Tre). 24 males treadmill walked in one of four conditions (1): 30 min at 3.0 mph and 0% grade, 20 °C and 50% relative humidity (RH), wearing healthcare worker (HCW) PPE; (2): 30 min at 3.0 mph and 0% grade, 27.5 °C and 60% RH, HCW PPE; (3): 30 min at 3.0 mph and 0% grade, 32.5 °C and 70% RH, HCW PPE; and (4): 40 min at 40% VO2max, 30 °C and 70% RH, wearing firefighter PPE. Trunk posture (Zephyr BioHarness 3) and Tre were measured continuously. Tre was positively related to trunk posture, controlling for covariates (B = 3.49, p < .001). BMI and age moderated this relationship (Tre×age, B = 0.76, p < .001; Tre*BMI, B = −1.85, p < .001). Trunk posture measurement may be useful in monitoring fall potential and magnitude of heat stress of workers in hot environments. Practitioner Summary: Occupational hyperthermia increases worker risk for heat illness and injury but is difficult to monitor in the field. This investigation shows that trunk posture is independently and positively related to core temperature. Non-invasive measurement or visual inspection of trunk posture could provide novel insight on individual heat strain level.