Impact of SCBA size and fatigue from different firefighting work cycles on firefighter gait

Risk of slips, trips and falls in firefighters maybe influenced by the firefighter’s equipment and duration of firefighting. This study examined the impact of a four self-contained breathing apparatus (SCBA) three SCBA of increasing size and a prototype design and three work cycles one bout (1B), two bouts with a five-minute break (2B) and two bouts back-to-back (BB) on gait in 30 firefighters. Five gait parameters (double support time, single support time, stride length, step width and stride velocity) were examined pre- and post-firefighting activity. The two largest SCBA resulted in longer double support times relative to the smallest SCBA. Multiple bouts of firefighting activity resulted in increased single and double support time and decreased stride length, step width and stride velocity. These results suggest that with larger SCBA or longer durations of activity, firefighters may adopt more conservative gait patterns to minimise fall risk.

Practitioner Summary: The effects of four self-contained breathing apparatus (SCBA) and three work cycles on five gait parameters were examined pre- and post-firefighting activity. Both SCBA size and work cycle affected gait. The two largest SCBA resulted in longer double support times. Multiple bouts of activity resulted in more conservative gait patterns.     

Review of: “Machine Intelligence 7”. Edited by Bernard Meltzeb and Donald Michie.(Edinburgh University Press, 1972.) [Pp. xiv+485.] £12.00.

To better assess the energy expenditure and exertion of firefighters during simulated firefighting activities, a commercial firefighter self-contained breathing apparatus (SCBA) facepiece was modified to interface with a portable metabolic monitoring device (Cosmed K4b²) while still functioning as a positive pressure SCBA air supply. To validate the device, standard National Fire Protection Association 1981 SCBA function tests were conducted and 14 subjects performed variable-workload assessments using all combinations of two test devices (Cosmed K4b² and metabolic cart) and two masks (modified SCBA facepiece and stock manufacturer-supplied breath collection). Metabolic data collected with the Cosmed K4b² via the modified facepiece were found to be accurate when compared to a ParvoMedics Truemax 2400 metabolic cart (average per cent difference: 4.6%). This modified facepiece design is suitable for use in metabolic studies requiring the utilisation of an SCBA system. Furthermore, the well-established overestimation of oxygen consumption from the Cosmed K4b² system was replicated.     

Effects of the self-contained breathing apparatus and fire protective clothing on maximal oxygen uptake

To examine the effects of firefighting personal protective ensemble (PPE) and self-contained breathing apparatus (SCBA) on exercise performance, 12 males completed two randomly ordered, graded exercise treadmill tests (GXTPPE and GXTPT). Maximal oxygen consumption (VO2max) during GXTPPE was 17.3% lower than the GXTPT in regular exercise clothing (43.0 +/- 5.7 vs. 52.4 +/- 8.5 ml/kg per min, respectively). The lower VO2max during the PPE condition was significantly related (r = 0.81, p < 0.05) to attenuated peak ventilation (142.8 +/- 18.0 vs. 167.1 +/- 15.6 l/min), which was attributed to a significant reduction in tidal volume (2.6 +/- 10.4 vs. 3.2 +/- 0.4 l). Breathing frequency at peak exercise was unchanged (55 +/- 7 vs. 53 +/- 7 breaths/min). The results of this investigation demonstrate that PPE and the SCBA have a negative impact on VO2max. These factors must be considered when evaluating aerobic demands of fire suppression work and the fitness levels of firefighters.     

Effect of wearing personal protective clothing and self-contained breathing apparatus on heart rate, temperature and oxygen consumption during stepping exercise and live fire training exercises

Fire fighter breathing apparatus instructors (BAIs) must possess the ability to respond to both the extrinsic stress of a high temperature environment and the intrinsic stress from wearing personal protective equipment (PPE) and self-contained breathing apparatus (SCBA), repeatedly and regularly, whilst training recruits in live fire training exercises (LFTEs). There are few previous investigations on BAIs in hot environments such as LFTEs, since the main research focus has been on regular fire fighters undertaking exercises in temperate or fire conditions at a moderate to high exercise intensity. In this study, the intrinsic cardiovascular stress effects of wearing PPE + SCBA were first investigated using a step test whilst wearing gym kit (control), weighted gym kit (a rucksack weighted to the equivalent of PPE + SCBA) and full PPE + SCBA (weight plus the effects of protective clothing). The extrinsic effects of the very hot environment were investigated in BIAs in LFTEs compared to mock fire training exercises (MFTEs), where the fire was not ignited. There was an increase in heart rate due to the modest workload imposed on the BAIs through carrying out the MFTEs (25.0 (18.7)%) compared to resting. However, when exposed to fire during the LFTEs, heat storage appears to be significant as the heart rate increased by up to 39.8 (+/-20.1)% over that of the mock LFTEs at temperate conditions. Thus, being able to dissipate heat from the PPE is particularly important in reducing the cardiovascular responses for BAIs during LFTEs.     

Effects of the self-contained breathing apparatus and fire protective clothing on maximal oxygen uptake

To examine the effects of firefighting personal protective ensemble (PPE) and self-contained breathing apparatus (SCBA) on exercise performance, 12 males completed two randomly ordered, graded exercise treadmill tests (GXT_PPE and GXT_PT). Maximal oxygen consumption (VO_2max) during GXT_PPE was 17.3% lower than the GXT_PT in regular exercise clothing (43.0 ± 5.7 vs. 52.4 ± 8.5 ml/kg per min, respectively). The lower VO_2max during the PPE condition was significantly related (r = 0.81, p < 0.05) to attenuated peak ventilation (142.8 ± 18.0 vs. 167.1 ± 15.6 l/min), which was attributed to a significant reduction in tidal volume (2.6 ± 10.4 vs. 3.2 ± 0.4 l). Breathing frequency at peak exercise was unchanged (55 ± 7 vs. 53 ± 7 breaths/min). The results of this investigation demonstrate that PPE and the SCBA have a negative impact on VO_2max. These factors must be considered when evaluating aerobic demands of fire suppression work and the fitness levels of firefighters.     

Psychophysiological responses in experienced firefighters undertaking repeated self-contained breathing apparatus tasks

In order to safely and effectively extinguish fires and rescue life, firefighters are required to routinely wear self-contained breathing apparatus (SCBA), yet little is known about the specific physiological and psychological demands associated with repeated exposure to tasks that require SCBA. A total of 12 experienced firefighters took part in a series of commonly encountered SCBA activities: free search, guideline search and live firefighting tasks under room temperature (～20°C) and extreme heat (～180°C) conditions to assess changes in heart rate, blood pressure, mood, perceived workload and air usage. Findings demonstrate that live firefighting is associated with greater perceived exhaustion than free search or guideline exercises; however, all tasks lead to high cardiovascular demand regardless of the presence of heat. No significant impact of task upon mood and no significant differences between the perceived demands of guideline, free search and live firefighting exercises were found.

Practitioner Summary: This study considered the physiological and psychological responses of firefighters undertaking SCBA exercises. Although live firefighting is associated with greater perceived exertion, the absence of differences in psychological domains between exercises demonstrates that task demands are not always dependent upon the presence of fire and that all tasks are mentally challenging.     

Physiological response to firefighting activities of various work cycles using extended duration and prototype SCBA

Firefighters’ self-contained breathing apparatus (SCBA) protects the respiratory system during firefighting but increases the physiological burden. Extended duration SCBA (>30 min) have increased air supply, potentially increasing the duration of firefighting work cycles. To examine the effects of SCBA configuration and work cycle (length and rest), 30 firefighters completed seven trials using different SCBA and one or two bouts of simulated firefighting following work cycles common in the United States. Heart rate, core temperature, oxygen consumption, work output and self-reported perceptions were recorded during all activities. Varying SCBA resulted in few differences in these parameters. However, during a second bout, work output significantly declined while heart rates and core temperatures were elevated relative to a single bout. Thirty seven per cent of the subjects were unable to complete the second bout in at least one of the two-bout conditions. These firefighters had lower fitness and higher body mass than those who completed all assigned tasks.

Practitioner Summary: The effects of extended duration SCBA and work/rest cycles on physiological parameters and work output have not been examined. Cylinder size had minimal effects, but extended work cycles with no rest resulted in increased physiological strain and decreased work output. This effect was more pronounced in firefighters with lower fitness.     

Skin sites to predict deep-body temperature while wearing firefighters’ personal protective equipment during periodical changes in air temperature

The aim of this study was to investigate stable and valid measurement sites of skin temperatures as a non-invasive variable to predict deep-body temperature while wearing firefighters’ personal protective equipment (PPE) during air temperature changes. Eight male firefighters participated in an experiment which consisted of 60-min exercise and 10-min recovery while wearing PPE without self-contained breathing apparatus (7.75 kg in total PPE mass). Air temperature was periodically fluctuated from 29.5 to 35.5 °C with an amplitude of 6 °C. Rectal temperature was chosen as a deep-body temperature, and 12 skin temperatures were recorded. The results showed that the forehead and chest were identified as the most valid sites to predict rectal temperature (R² = 0.826 and 0.824, respectively) in an environment with periodically fluctuated air temperatures. This study suggests that particular skin temperatures are valid as a non-invasive variable when predicting rectal temperature of an individual wearing PPE in changing ambient temperatures.

Practitioner Summary: This study should offer assistance for developing a more reliable indirect indicating system of individual heat strain for firefighters in real time, which can be used practically as a precaution of firefighters’ heat-related illness and utilised along with physiological monitoring.     

Effects of firefighters' self-contained breathing apparatus' weight and its harness design on the physiological and subjective responses

To examine the effects of firefighters' self-contained breathing apparatus' (SCBA) weight and its harness design on the physiological and subjective responses, eight male students performed treadmill exercise under four conditions: the 8 kg firefighter protective clothing (PC) (Control), the PC + an 11 kg SCBA with an old harness (Test A), the PC + a 6.4 kg SCBA with an old harness (Test B) and the PC + a 6.4 kg SCBA with a new harness (Test C), at ambient temperatures (T(a)) of 22°C and 32°C. Besides highlighting the fact that a heavy SCBA had a significant effect on the oxygen consumption and metabolic rate, this experiment also found that in a T(a) of 32°C, in particular, the combined effect of 4.7 kg lighter SCBA and new harness design could reduce metabolic rate and improved subjective muscle fatigue and thermal discomfort. PRACTITIONER SUMMARY: An effort to alleviate the physiological and subjective burden of firefighters by reducing the weight of SCBA and by using the new harness design has provided satisfactory results in reduced oxygen consumption and in improved subjective responses in a hot air environment.     

Measuring the effects of structural turnout suits on firefighter range of motion and comfort

Abstract

Range of motion (ROM) can be restricted by wearing stiff and bulky clothing. This is particularly true of firefighter suits that are constructed using fabric layers to provide thermal protection from fire. This study developed an evaluation technique to quantify the loss of mobility associated with wearing firefighters’ protective suits that were deliberately selected to represent similar ergonomic design features. The ROM of 10 firefighters was measured using electro-goniometers attached to their bodies while they wore uniforms and a reference outfit, and performed specific movements. The most restrictive uniform is the Bulky suit that contained additional layers of materials in sleeves and on the knees. The Traditional Suit was more ROM restrictive than Ergonomic. The subjective evaluation of suits supported the objective assessments provided by the electro-goniometers. A 3-D body scanning technique was employed to establish a correlation between the bulkiness of firefighter outfits and subject ROM.

Practitioner Summary: This study presents a methodology for measurements of range of motion (ROM) in firefighters wearing personal protective equipment (PPE). Even small differences in designs of PPE may impact firefighters’ ROM, which can be detected by electro-goniometers providing measurements if they are attached along the joint to measure limb angular movement.     

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.     

The influence of firefighter boot type on balance

A firefighter's boots play a critical role in working effectiveness and personal safety. OSHA 1910.156 contains standards for personal protective equipment of fire brigades. Firefighters use either rubber or leather boots that meet these requirements. The purpose of the study was to examine the differences in balance in professional firefighters wearing rubber and leather boots when participating in a fire simulation activity. Twelve professional firefighters performed 2 sets of a three-minute simulated firefighter stair climb wearing a 50 lb weighted vest to simulate their typical personal protective equipment and two 5.68 kg weights on the shoulders to simulate the weight of a high-rise pack (hose bundle). On each condition day (leather, rubber) the firefighter conducted a balance assessment. Following the initial balance protocol, the firefighter conducted a Simulated Firefighter Stair Climb for 3 min at a rate of 60 steps per/min. At the completion of the stair climb, the firefighter repeated the balance procedure. Following a 3-minute rest period, the complete procedure (balance, stair climb) was repeated. A total of 3 balance procedures and 2 stair climbs were completed. Significant differences were found in sway velocity between the pre and post test measures and among the two different boots. These results suggest that the rubber boots elicit greater postural instability. These findings provide practical information on work practices and PPE usage decisions.Relevance to industryIndustry standards dictate the protective variables of boots used by fire brigades, but do not consider the influence on gait and balance. This study provides evidence that the rubber boots used by firefighters may impair specific balance parameters which are critical for firefighter safety.     

Effect of wearing personal protective clothing and self-contained breathing apparatus on heart rate,temperature and oxygen consumption during stepping exercise and live fire training exercises

Fire fighter breathing apparatus instructors (BAIs) must possess the ability to respond to both the extrinsic stress of a high temperature environment and the intrinsic stress from wearing personal protective equipment (PPE) and self-contained breathing apparatus (SCBA), repeatedly and regularly, whilst training recruits in live fire training exercises (LFTEs). There are few previous investigations on BAIs in hot environments such as LFTEs, since the main research focus has been on regular fire fighters undertaking exercises in temperate or fire conditions at a moderate to high exercise intensity. In this study, the intrinsic cardiovascular stress effects of wearing PPE + SCBA were first investigated using a step test whilst wearing gym kit (control), weighted gym kit (a rucksack weighted to the equivalent of PPE + SCBA) and full PPE + SCBA (weight plus the effects of protective clothing). The extrinsic effects of the very hot environment were investigated in BIAs in LFTEs compared to mock fire training exercises (MFTEs), where the fire was not ignited. There was an increase in heart rate due to the modest workload imposed on the BAIs through carrying out the MFTEs (25.0 (18.7)%) compared to resting. However, when exposed to fire during the LFTEs, heat storage appears to be significant as the heart rate increased by up to 39.8 (±20.1)% over that of the mock LFTEs at temperate conditions. Thus, being able to dissipate heat from the PPE is particularly important in reducing the cardiovascular responses for BAIs during LFTEs.     

The effect of hyperoxia on submaximal exercise with the self-contained breathing apparatus

The effects of hyperoxia on submaximal exercise with the self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed a graded exercise test for the determination of ventilatory threshold (VT) and then a submaximal practice trial with a normoxic gas mixture. The normoxic (20.93 +/- 0.22% O(2); SUB(21)) and hyperoxic (40.18 +/- 0.73% O(2); SUB(40)) submaximal trials were then administered in a random order. All exercise tests were completed on separate days while wearing firefighting gear and the SCBA. Compared with SUB(21), hyperoxia significantly reduced minute ventilation (V(E)), mask pressure (P(mask)), heart rate, blood lactate concentration, perceived exertion, and perceived breathing distress. As expected, hemoglobin saturation remained higher (p < 0.05) during SUB(40). The reductions in both V(E) and P(mask) with hyperoxia imply a reduction in the work of breathing during exercise. Total gas consumption was 10.3 +/- 8.1% lower during SUB(40) when compared to SUB(21), another finding that has significant practical implications for occupational safety.     

Component contribution of personal protective equipment to the alleviation of physiological strain in firefighters during work and recovery

The purpose of this study was to investigate the components contributions of personal protective equipment on physiological strain in firefighters during exercise and recovery. Eight firefighters participated in trials in which various combinations of personal protective equipment components weighing from 1.3 to 15.1 kg were worn. The results showed that rectal temperature, changes in rectal temperature, mean skin temperature, heart rate, oxygen consumption and blood lactate concentration were smaller in conditions without boots (no-boots) than in other conditions with no helmet, gloves or self-contained breathing apparatus (P < 0.05). Increases in rectal temperature per unit mass of personal protective equipment were approximately twice as small in no-boots condition as the other conditions. These results suggest that the reduction of the boots' mass might be more efficient to alleviate heat strain of firefighters wearing personal protective equipment, rather than the reduction of the mass of self-contained breathing apparatus, helmet or gloves.     

The effect of hyperoxia on submaximal exercise with the self-contained breathing apparatus

The e^ffects of hyperoxia on submaximal exercise with the self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed a graded exercise test for the determination of ventilatory threshold (VT) and then a submaximal practice trial with a normoxic gas mixture. The normoxic (20.93 ± 0.22% O₂ ; SUB₂₁) and hyperoxic (40.18 ± 0.73% O₂; SUB₄₀) submaximal trials were then administered in a random order. All exercise tests were completed on separate days while wearing firefighting gear and the SCBA. Compared with SUB₂₁, hyperoxia significantly reduced minute ventilation ([Vdot]_E ), mask pressure (P_mask), heart rate, blood lactate concentration, perceived exertion, and perceived breathing distress. As expected, hemoglobin saturation remained higher (p<0.05) during SUB₄₀. The reductions in both [Vdot]_E and P_mask with hyperoxia imply a reduction in the work of breathing during exercise. Total gas consumption was 10.3 ± 8.1% lower during SUB₄₀ when compared to SUB₂₁, another finding that has significant practical implications for occupational safety.     

Hyperoxia improves maximal exercise with the self-contained breathing apparatus (SCBA)

The effects of hyperoxia on maximal exercise while breathing from a self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed three graded exercise tests (GXT) for the assessment of maximal oxygen uptake (Vdot;O _2max): two with 20.95 ± 0.28% O₂ and the third (GXT₄₀) while breathing hyperoxia (40.64 ± 1.29% O₂). No significant differences were found between the two normoxic tests, except for a 16W increase in maximal power output (PO_max) in the second trial (GXT₂₁). Compared to GXT₂₁, hyperoxia significantly increased Vdot;O _2max and PO_max by 10.0 ± 3.8% and 10.2 ± 7.1%, respectively. This was likely due to an increase in O₂ delivery as suggested by the significantly higher oxyhemoglobin saturation. The increase in Vdot;O _2max with hyperoxia was similar to the increase in carbon dioxide production (9.3 ± 6.5%). No other significant differences were found at maximal exercise. However, at the intensity that elicited Vdot;O _2max in GXT₂₁, pulmonary ventilation and SCBA mask pressure were significantly lower during GXT₄₀, suggesting a decrease in the work of breathing. These findings could have significant implications for occupations that involve heavy work with SCBA.     

Hyperoxia improves maximal exercise with the self-contained breathing apparatus (SCBA)

The effects of hyperoxia on maximal exercise while breathing from a self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed three graded exercise tests (GXT) for the assessment of maximal oxygen uptake (VO(2max)): two with 20.95 +/- 0.28% O(2) and the third (GXT(40)) while breathing hyperoxia (40.64 +/- 1.29% O(2)). No significant differences were found between the two normoxic tests, except for a 16W increase in maximal power output (PO(max)) in the second trial (GXT(21)). Compared to GXT(21), hyperoxia significantly increased VO(2max) and PO(max) by 10.0 +/- 3.8% and 10.2 +/- 7.1%, respectively. This was likely due to an increase in O(2) delivery as suggested by the significantly higher oxyhemoglobin saturation. The increase in VO (2max) with hyperoxia was similar to the increase in carbon dioxide production (9.3 +/- 6.5%). No other significant di.fferences were found at maximal exercise. However, at the intensity that elicited VO(2max) in GXT(21), pulmonary ventilation and SCBA mask pressure were significantly lower during GXT(40), suggesting a decrease in the work of breathing. These findings could have significant implications for occupations that involve heavy work with SCBA.     

Evaluation of performance and load in simulated rescue tasks for a novel design SCBA: effect of weight,volume and weight distribution

A self-contained breathing apparatus (SCBA) with an innovative rucksack shape that provides a better distribution of its weight over the middle and lower parts of the back (device C: 6l, 13.7 kg) was compared with two conventional SCBA which differed from each other in volume and weight (A: 6l, 15 kg, B: 6.8l, 11.7 kg). Twelve fire-fighters (27-49 yr) performed three exercises while using the three SCBA in a systematically permuted sequence. The exercises consisted of simulated rescue work under natural climatic conditions in a dwelling on the second floor and several typical elements of severe fire-fighting actions. Duration, heart rate, breathing frequency, rectal temperature, and sweat loss were recorded. Perceived exertion was rated and the carrying features of the SCBA were subjectively evaluated. The exercise was executed faster with the rucksack device, heart rates were then lower and the carrying features were evaluated as better. Thus, the weight of the SCBA was shown to be less important than its distribution.     

Physiological demand on firefighters crawling during a search exercise

This study was an investigation into the physiologic demands of crawling for firefighter trainees performing the search portion of a ‘search and rescue’ (SAR) exercise. A total of twenty-five male subjects participated in the exercise, each of whom provided demographic data, body part discomfort before and after the exercise, and air consumption data from their self-contained breathing apparatus (SCBA) during the exercise. A subset (n = 14) of these subjects also wore heart rate monitors during the search exercise, which involved crawling in full turnout gear. Results demonstrated a dramatic increase in heart rates during crawling activities. The maximum heart rate during crawling averaged 174 beats per minute (bpm) (∼88% of their mean age-predicted maximum heart rate), about 97 bpm higher than their standing resting heart rate. The duration of the crawling search exercise ranged from 14.4 to 21.0 min. The volume of air consumed from the SCBA's averaged 52.9 L/Min (SD = 10.1). Five subjects (20%) exhausted their air before completing the exercise, and an additional sixteen subjects (64%) finished with critically low levels of reserve air. Crawling was observed to be a mode of locomotion that required extremely high cardiorespiratory demands, even in the absence of the thermal load that would be experienced in an actual fire event. The high cardiac load associated with crawling in turnout gear may increase the risks of heat-related illnesses and cardiac events during firefighter search and rescue activities.Relevance to industryThe findings in this paper can help Fire Department Training Officers appreciate the magnitude of cardiac loading associated with firefighter crawling exercises in Bunker Gear. This awareness, coupled with commercially available physiological monitoring equipment and the minimization of exercise duration and intensity, has the potential to lower the risk associated with such physically demanding training exercises.