194
Clinical methods and pathophysiology
Blood pressure and heart rate responses in volunteer firefighters while wearing personal protective equipment Deborah L. Feairheller Background Hypertension, cardiovascular disease, and obesity are global health problems and are a large concern for firefighters. The leading cause of death among firefighters is cardiac-related; hence, it is important to understand how firefighter personal protective equipment (PPE) affects cardiovascular responses to different activities. Volunteer firefighters represent 70% of all firefighters and are an understudied population. To the best of our knowledge, this is the first study to report blood pressure (BP) responses in volunteer firefighters. Methods and results Thirty-six male, nonsmoking volunteer firefighters (27.8 ± 9.7 years) underwent two maximal treadmill tests within 2 weeks, one in regular gym clothes and one in PPE. We found that while wearing PPE, which weighs 54.2 ± 3.5 lbs, BP responses are exaggerated during work and in recovery. Systolic BP and heart rate were significantly (P < 0.05) higher at each submaximal stage and during active recovery of the PPE test compared with the regular clothing test (15–23 mmHg and 20–34 bpm higher, respectively). Test time and VO2 max were lower in the PPE test (P < 0.05).
Introduction Hypertension, cardiovascular disease, and obesity are global health problems [1,2]. Hypertension has a direct relationship with increased body weight and risk for cardiac incidents [3]. Firefighting is one of the most hazardous and dangerous jobs, with an inherently increased risk of death; many firefighters have hypertension, and the leading cause of death in firefighters is cardiac-related [4,5]. Research on male firefighters recently reported that the predictors of on-duty cardiac deaths include increased blood pressure (BP), previous heart disease, obesity, and smoking status [4,6]. BP awareness continues to be low, whereas hypertension rates continue to be high [2]. Hypertension control also remains a problem among both the general population and firefighters [1,7]. Supporting this, Soteriades et al. [7] reported that 74% of hypertensive firefighters did not have adequate control of their BP. Thus, it is important to increase the awareness of BP levels in firefighters, both at rest and under different work conditions. Environmental hazards require that firefighters wear personal protective equipment (PPE) which contains a self-contained breathing apparatus (SCBA). The SCBA provides a controlled environment of safe pressurized air through the use of a full facemask and a regulator system. 1359-5237 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Conclusion BP responses are exaggerated while wearing full fire protective gear and remain elevated during recovery. Awareness of how firefighting activities affect BP is important; so future studies should examine how the BP increase relates to resting BP levels, to PPE weight, and to the thermal effects of the PPE. Blood Press Monit 20:194–198 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Blood Pressure Monitoring 2015, 20:194–198 Keywords: blood pressure, cardiovascular health, exercise, firefighters, self-contained breathing apparatus The HEART (Hypertension and Endothelial function with Aerobic and Resistance Training) Laboratory, Department of Health & Exercise Physiology, Ursinus College, Collegeville, Pennsylvania, USA Correspondence to Deborah L. Feairheller, PhD, The HEART (Hypertension and Endothelial function with Aerobic and Resistance Training) Laboratory, Department of Health & Exercise Physiology, Ursinus College, 601 E. Main Street, Collegeville, PA 19426, USA Tel: + 1 6100 409 3256; e-mail: [email protected] Received 11 January 2015 Revised 4 March 2015 Accepted 10 March 2015
Firefighting, while wearing full PPE, imposes significant cardiovascular strain because of the heavy physical workload, weight of the SCBA, limited mobility, thermal effects, and impaired balance and visibility that heavy gear can cause [8–13]. Despite improvements in design and weight of both PPE and SCBA, evidence still suggests that the increased stress affects many cardiovascular variables; however, BP has not been examined. The cardiovascular effects of wearing PPE with SCBA have been tested in college male individuals and career firefighters, but limited research has been conducted on volunteer firefighters [14–17]. Tests have been performed in different PPE configurations, and all have reported that heart rate (HR) was higher and VO2 max was lower in the experimental group when compared with the a control group (regular gym clothing) [14–17]. Separate studies have also examined HR and thermal effects of firefighting under different temperature conditions [13]. Yet, none of these studies have reported BP responses. Importantly, participants in all of these studies had carried the SCBA but were not breathing through the SCBA regulator. During structural fire suppression or rescue work, firefighters wear their full PPE, as well as breathe through the SCBA. To the best of our knowledge, only two exercise studies have been performed where the DOI: 10.1097/MBP.0000000000000120
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Blood pressure responses in volunteer firefighters Feairheller 195
participants were asked to breathe through the SCBA regulator [18,19]. Both studies reported that the added resistance from the SCBA regulator may have contributed to a lower VO2max when compared with the control group, but neither reported BP responses. Currently, volunteer firefighters represent 70% of the total firefighting population, and thus are an important population to study [20]. The prevalence of cardiovascular risk factors, including elevated BP, is higher in firefighters than in the general population [2,21,22]. Considering the higher cardiovascular risk that firefighters face, the low levels of BP awareness, and the fact that research on BP of firefighters is extremely limited, the purposes of this study were to examine BP and HR responses to work (through the maximal-graded treadmill test) in volunteer firefighters while wearing full PPE + SCBA, as used during fire suppression activity.
Methods Participants
Forty-five volunteer firefighters from around the Philadelphia suburban area were recruited by word of mouth or contacted researchers after seeing media news articles [23]. Thirty-six were included in the analysis, because they met the inclusion criteria and completed both treadmill tests. Criteria for inclusion were: male volunteer firefighter, no prior cardiovascular incidents, no diagnosed heart disease or diabetes, nonsmoker, and completion of both treadmill tests within a 2-week period. Sex differences exist in rates of high BP and in response to exercise; hence, female firefighters were not included [24]. Each firefighter gave informed consent and completed a general health history form. The protocol was approved by the Ursinus College Institutional Review Board, and all procedures were in accordance with the ethical standards of the Helsinki Declaration. Study protocol
This was a single-group cross-over study. All enrolled firefighters underwent two maximal treadmill tests within a 2-week period, at the same time of day: one in regular gym clothes and sneakers (regular test), and one in full firefighter PPE (PPE test). Full firefighter PPE included boots, pants, a jacket, gloves, and a helmet, along with the SCBA air pack and face mask system. Firefighters were asked to breathe air through the SCBA regulator during the PPE test. During the PPE test, the right sleeve was turned inside out and tucked inside the jacket, so that exercise BP measurements could be taken. Before each test, body weight was measured in regular clothing (for regular test) and in full PPE + SCBA (for PPE test). Resting and exercise BP levels were measured according to published guidelines [2]. In brief, BP measurements were performed by auscultation with a mercury sphygmomanometer, the first and fifth Korotkoff sounds corresponding to systolic and diastolic
BP. The measurements were taken at the following time points: before exercise at rest, during exercise at the last minute of each stage, after exercise at 2 and 4 min during active cool down, and after exercise during a seated recovery. BP measurements were taken using a correct size arm cuff, with the arm supported at the same level as the heart. All BP measurements were taken by the same operator, using the same sphygmomanometer. Treadmill test
A maximal symptom-limited Bruce protocol exercise stress test was performed. BP and perceived exertion were measured at each stage. HR (Polar Electro Inc., Lake Success, New York) was monitored at each minute of exercise. ECG was monitored during the regular test (Nasiff CardioCard; Nasiff Associates Inc., New York, New York, USA). The treadmill test was terminated using criteria according to guidelines [25]. Postexercise BP and HR were monitored during active recovery (1.7 mph, 0% grade) at 2 and 4 min after test termination. Postexercise BP and HR were also measured at 6 min after test termination, while the firefighter was seated with his feet flat on the floor. VO2max levels were calculated using the Bruce protocol test time formula [26]. Statistical analyses
Significance was set at P less than 0.05. Data are expressed as mean ± SD. All statistical analyses were carried out using SPSS version 19.0 (SPSS Inc., Chicago, Illinois, USA). The distribution of all variables was examined using the Shapiro–Wilk test of normality. Repeated measures analysis of variance was carried out to examine whether any condition (i.e. PPE, regular) by time (i.e. stage BP, minute HR) interaction effect existed. Post-hoc within-group analysis was carried out using paired t-tests to compare values between timepoints. Between group analyses were carried out using independent t-tests to determine whether there were significant differences between the regular test group and the PPE test group at each timepoint. Pearson’s correlation was used to determine whether there were relationships between variables, and this was further examined by linear regression analysis. Data were also covaried for body weight, gear weight, age, maximum systolic BP, and VO2max.
Results Thirty-six male volunteer firefighters (27.8 ± 9.7 years) completed the study. Table 1 presents the participant characteristics. The average weight of the firefighting PPE was 54.2 ± 3.5 lbs. The volunteer firefighters had several cardiovascular risk factors, confirming what other studies have found [7,21]. The average BMI of the firefighters was 30.8 ± 6.3 kg/m2, with most participants being overweight (23%) or obese (44%), similar to other studies [21] The average resting BP of the firefighters was 129.4/75.1 mmHg, which is classified as prehypertension.
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Blood Pressure Monitoring 2015, Vol 20 No 4
Volunteer firefighter characteristics
None of the firefighters included in this study were on medication for BP. The volunteers had an average of 9.25 years of service, responded to 13.7 emergency calls a month, and attended 2.9 trainings a month. The National Fire Protection Association has established that the demands on the cardiovascular system require a fitness level of at least 12 metabolic equivalents (METs), which is the equivalent of a VO2max of 42 kg/ml/min [27]. The volunteer firefighters in our study reportedly exercised only 1.9 times per week and had an estimated average VO2max of 37.7 ± 7.2 ml/kg/min, which is below the National Fire Protection Association recommendations. Exercise test responses between personal protective equipment and regular tests
The physiological responses at maximum exercise are shown in Table 2. The total test time was significantly shorter for the PPE test (7.2 ± 0.8 min) compared with the regular test (10.7 ± 1.8 min, P < 0.05), and the estimated VO2max was lower for the PPE test (24.2 ± 2.7 ml/kg/min) compared with the regular test (37.8 ± 7.2 ml/kg/min). Systolic BP responses to exercise are shown in Fig. 1. Mauchley’s test of sphericity indicated that the assumption of sphericity had been violated [χ2(5) = 21.02, P < 0.01]; therefore, a Greenhouse–Geisser correction was used. There was a significant effect of condition on systolic BP (P = 0.000). Post-hoc pairwise comparisons revealed that systolic BP was significantly higher
∗ ∗
Re 2 m co in ve ry Re 4 m co in ve ry 6 Se m at in ed
M ax
2 ge
ge
St a
g
1
∗
St a
Data are presented as mean ± SD. DBP, diastolic blood pressure; PPE, personal protective equipment; SBP, systolic blood pressure; VO2, oxygen consumption.
FF: Reg FF: PPE
220 210 200 190 180 170 160 150 140 130 120 tin
Value 27.8 ± 9.7 70.6 ± 3.0 212.2 ± 41.6 30.8 ± 6.3 129.4 ± 9.7 75.1 ± 6.9 75.7 ± 12.5 54.2 ± 3.5 13.7 ± 6.1 2.9 ± 1.1 9.3 ± 9.4 1.9 ± 1.7 37.7 ± 7.2
Age Height (inches) Body weight (lb) BMI (kg/m2) Resting SBP (mmHg) Resting DBP (mmHg) Resting heart rate (bpm) Weight of PPE (lb) Emergency calls responded to/month Trainings attended/month Years in service Times exercise/week VO2max (ml/kg/min)
Re s
Variable (N = 36)
Fig. 1
Systolic blood pressure (mmHg)
Table 1
Comparison of systolic blood pressure responses at each stage of a Bruce protocol exercise test, between regular clothing (solid bars) and full firefighter personal protective equipment (PPE, open bars), during active recovery (1.7 mph, 0%), measured at 2 and 4 min during recovery, and at 6 min after exercise while seated. *Significance: P < 0.05 between groups. FF, firefighter; PPE, personal protective equipment.
(15–23 mmHg higher) at each submaximal stage of the PPE test compared with the regular test (P < 0.05). In addition, systolic BP at 2 min active recovery was higher during the PPE test compared with the regular test (P < 0.05). HR responses to exercise are shown in Fig. 2. There was a significant effect of condition on HR (P = 0.000). Posthoc pairwise comparisons revealed that HR was significantly higher (20–34 bpm higher) at each submaximal minute of the PPE test compared with the regular test (P < 0.05). In addition, HR at 2 min and 4 min active recovery was higher during the PPE test compared with the regular test (P < 0.05). Fig. 2
FF: Reg FF: PPE
190 Heart rate (bpm)
196
170 150 ∗
130
∗
∗
∗
∗
∗ ∗
∗ ∗ ∗
110 90
Data are expressed as mean ± SD. DBP, diastolic blood pressure; PPE, personal protective equipment; SBP, systolic blood pressure; VO2, oxygen consumption. *Significance: P < 0.05 between groups.
8 Re Ma in cov x R e 6 eco ry m in ver Se y at ed
7
6
5
4
3
2
in
m
216.7 ± 11.6 79.8 ± 6.3 185.8 ± 8.8 24.2 ± 2.7* 7.2 ± 0.8*
m
PPE test
211.4 ± 14.6 78.8 ± 6.1 191.5 ± 25.2 37.8 ± 7.2 10.7 ± 1.8
4
Regular test
SBP max (mmHg) DBP max (mmHg) Heart rate max (mmHg) VO2max (ml/kg/min) Total exercise time (min)
2
Variable (N = 36)
Re
st in
g
Responses to exercise test
1
70 Table 2
Comparison of heart rate responses during each minute of a Bruce protocol exercise test, between regular clothing (solid bars) and full firefighter personal protective equipment (PPE, open bars), during active recovery (1.7 mph, 0%), measured at 2 and 4 min, and at 6 min after exercise while seated. *Significance: P < 0.05 between groups. FF, firefighter; PPE, personal protective equipment.
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Blood pressure responses in volunteer firefighters Feairheller 197
We found no differences in maximal BP or HR levels.
Discussion The main finding of this study is that volunteer firefighters have exaggerated systolic BP and HR levels during each stage of incremental exercise, as well as during recovery time, while wearing full PPE and SCBA. To date, most studies on firefighters have included career firefighters or mixed populations of career and volunteer firefighters, and the studies have included smokers. In a population of volunteer firefighters, we confirmed what other studies have reported; firefighters may have increased cardiovascular risk [4,5,7]. The volunteer firefighters in our study were inactive, had low fitness levels, were overweight or obese, and had prehypertension. Research consistently shows that low cardiorespiratory fitness is related to cardiovascular events, hypertension, and mortality [28,29]. Furthermore, it is known that BP responses to exercise differ for normotensive compared with hypertensive individuals [2,30]. To the best of our knowledge, this is the first study to report BP levels in firefighters during activity. In general, physical activity leads to an increase in cardiac output to perfuse the working muscle beds [31]. Sympathetic activity increases, leading to a rise in systolic BP and HR. The normal systolic BP increase for men at stage 1 of the Bruce protocol is 20–30 mmHg and at the maximal stage is 50–60 mmHg, compared with resting levels [31]. In our study, for firefighters wearing PPE, we found that systolic BP increased from resting levels by 35 mmHg at stage 1 and by 87 mmHg at the maximal stage. Considering that firefighters work in extremely stressful environments, with high physical demands, while wearing heavy, thickly insulated and fully encapsulating clothing, we would expect that BP and HR would increase more than under the baseline condition [32]. However, the relationship between the magnitude of the BP elevation and different gear weights or configurations needs to be elucidated. No other study on firefighters has measured BP during activity; thus, this is the first step toward understanding BP responses to work while wearing PPE. Our results suggest that either the weight or the thermal insulation effects of the PPE aggravate the BP responses to exercise. We also found that recovery systolic BP and recovery HR were exaggerated in firefighters wearing PPE. Once activity stops, systolic BP is expected to decline rapidly after exercise, and recovery BP responses are thought to provide prognostic information. The proper timeline needed for recovery from firefighting activities has yet to be established. In the general population, elevated postexercise systolic BP has been related to an increased risk for future hypertension or myocardial infarction [33]. A 3 min SBP ratio (SBP at 3 min after exercise/SBP at max) over 0.9 has been used to evaluate the risk for heart disease in prior studies [33]. None of the firefighters in
our study had a ratio over 0.9 (data not shown), which suggests a relative lack of overt heart disease in our population. In 2011, Horn et al. [34] reported that the recovery timeline from firefighting activities may be significantly longer than the typical 10–15 min rehabilitation that firefighters are supposed to follow. In their study, BP was measured before and after firefighting activity, after rehabilitation (15 min after exercise), and every 30 min for 2 h, in both career and volunteer firefighters. They found that systolic BP dropped during rehabilitation (measured at 15 min after exercise) [34]. In our study, under the PPE condition, firefighters had significantly higher systolic BP during active recovery compared with firefighters in regular clothing, suggesting that the PPE aggravates BP. Recent studies have reported strong relationships between a slower HR recovery and cardiovascular disease [35]. An exaggerated HR level during recovery could be due to peripheral resistance, metabolic disorder, or other vasoregulatory causes. Smith et al. [9] reported recovery HR levels in a mixed population of career and volunteer firefighters. They found that HR was still elevated at 8 and 16 min after firefighting activity compared with resting levels. Horn et al. [34] reported that HR remained elevated for 70–100 min after firefighting drills. Both studies suggest that when active fire suppression or heavy firefighting work is in progress, rehabilitation times should be observed. Our study is the first to report active recovery and immediate postexercise recovery seated BP and HR levels. Future studies are needed to understand how different conditions affect cardiovascular recovery in firefighting. We recognize that our study has several limitations. For the PPE test, the bunker coat sleeve was turned inside out; hence, the true BP response to thermal conditions may not have been measured, but this study was designed to examine the effects of weight (PPE + SCBA) and increased workload (treadmill stress test) on BP responses. The thermal effects on BP can be addressed in a future study. In addition, our study included only male, nonsmoking, volunteer firefighters; hence, results cannot be generalized to the entire firefighter population. Future studies can examine BP responses in other populations. Conclusion
This is the first study to report BP responses in volunteer firefighters to an exercise stress test. We found that while wearing full PPE and SCBA, the same configuration of protective gear used during fire suppression and rescue activities, BP at each submaximal workload was significantly higher compared with BP in regular gym clothes. These data suggest the need for further research on BP responses to different workloads in volunteer firefighters. High BP is a chronic health problem in society. Firefighters are at an increased risk for high BP,
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198 Blood Pressure Monitoring 2015, Vol 20 No 4
and those with elevated BP may not have it under control. The leading cause of firefighter fatalities remains cardiovascular; hence, research needs to understand how the protective gear that firefighters wear affects their cardiovascular responses, in particular, BP.
Acknowledgements The authors thank the volunteer firefighters for their participation in the study: fire stations in Pennsylvania included Collegeville, Trappe, Upper Frederick, and Lower Providence from Montgomery County; Reading from Berks County; and East Brandywine, Thorndale, and Oxford from Chester County. They also thank Matthew Generotti for help with the initial research design. Further, they thank the HEART lab research students who participated in data collection, including: Kristin Aichele, Joy Oakman, Avery Perez, Christina Cromwell, Mike Neal, and Jessica Lenzo.
13 14
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18
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21 22
Conflicts of interest
There are no conflicts of interest.
23
References
24
1
Go AS, Mozaffarian D, Roger VL, Benjamin EJ, Berry JD, Blaha MJ, et al. Heart disease and stroke statistics – 2014 update: a report from the American Heart Association. Circulation 2014; 129:e28–e292. 2 Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL, et al. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA 2003; 289:2560–2572. 3 Landsberg L, Aronne LJ, Beilin LJ, Burke V, Igel LI, Lloyd-Jones D, et al. Obesity-related hypertension: pathogenesis, cardiovascular risk, and treatment – a position paper of The Obesity Society and The American Society of Hypertension. Obesity 2013; 21:8–24. 4 Yang J, Teehan D, Farioli A, Baur DM, Smith D, Kales SN. Sudden cardiac death among firefighters < 45 years of age in the United States. Am J Cardiol 2013; 112:1962–1967. 5 Kahn SA, Woods J, Rae L. Line of duty firefighter fatalities: an evolving trend over time. J Burn Care Res 2015; 36:218–224. 6 Geibe JR, Holder J, Peeples L, Kinney AM, Burress JW, Kales SN. Predictors of on-duty coronary events in male firefighters in the United States. Am J Cardiol 2008; 101:585–589. 7 Soteriades ES, Kales SN, Liarokapis D, Christiani DC. Prospective surveillance of hypertension in firefighters. J Clin Hypertens (Greenwich) 2003; 5:315–320. 8 Fernhall B, Fahs CA, Horn G, Rowland T, Smith D. Acute effects of firefighting on cardiac performance. Eur J Appl Physiol 2012; 112:735–741. 9 Smith DL, Manning TS, Petruzzello SJ. Effect of strenuous live-fire drills on cardiovascular and psychological responses of recruit firefighters. Ergonomics 2001; 44:244–254. 10 Hooper AJ, Crawford JO, Thomas D. An evaluation of physiological demands and comfort between the use of conventional and lightweight self-contained breathing apparatus. Appl Ergon 2001; 32:399–406. 11 Kong PW, Suyama J, Cham R, Hostler D. The relationship between physical activity and thermal protective clothing on functional balance in firefighters. Res Q Exerc Sport 2012; 83:546–552. 12 Bakri I, Lee JY, Nakao K, Wakabayashi H, Tochihara Y. Effects of firefighters' self-contained breathing apparatus’ weight and its harness design on the physiological and subjective responses. Ergonomics 2012; 55:782–791.
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Skoldstrom B. Physiological responses of firefighters to workload and thermal stress. Ergonomics 1987; 30:1589–1597. Lee JY, Bakri I, Kim JH, Son SY, Tochihara Y. The impact of firefighter personal protective equipment and treadmill protocol on maximal oxygen uptake. J Occup Environ Hyg 2013; 10:397–407. Smith DL, Fehling PC, Hultquist EM, Lefferts WK, Barr DA, Storer TW, Cooper CB. Firefighter’s personal protective equipment and the chronotropic index. Ergonomics 2012; 55:1243–1251. Dreger RW, Jones RL, Petersen SR. Effects of the self-contained breathing apparatus and fire protective clothing on maximal oxygen uptake. Ergonomics 2006; 49:911–920. Bruce-Low SS, Cotterrell D, Jones GE. 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. Ergonomics 2007; 50:80–98. Eves ND, Jones RL, Petersen SR. The influence of the self-contained breathing apparatus (SCBA) on ventilator function and maximal exercise. Can J Appl Physiol 2005; 30:507–519. Louhevaara V, Smolander J, Korhonen O, Tuomi T. Maximal working times with a self-contained breathing apparatus. Ergonomics 1986; 29:77–85. Karter MJ, Stein GP. US fire department profile. National Fire Protection Association Report. Oct 2013. Available at: http://www.nfpa.org [Accessed November 2014]. Yoo HL, Franke WD. Prevalence of cardiovascular disease risk factors in volunteer firefighters. J Occup Environ Med 2009; 51:958–962. Storer TW, Dolezal BA, Abrazado ML, Smith DL, Batalin MA, Tseng CH, Cooper CB. PHASER Study Group. Firefighter health and fitness assessment: a call to action. J Strength Cond Res 2014; 28:661–671. McCarthy E. Ursinus professor aiming to keep firefighters’ hearts safe. The Philadelphia Inquirer. 2014. Available at: http://articles.philly.com [Accessed October 2014]. Ong KL, Tso AW, Lam KS, Cheung BM. Gender difference in blood pressure control and cardiovascular risk factors in Americans with diagnosed hypertension. Hypertension 2008; 51:1142–1148. Fletcher GF, Ades PA, Kligfield P, Arena R, Balady GJ, Bittner VA, et al. Exercise standards for testing and training: a scientific statement from the American Heart Association. Circulation 2013; 128:873–934. Foster C, Jackson AS, Pollock ML, Taylor MM, Hare J, Sennett SM, et al. Generalized equations for predicting functional capacity from treadmill performance. Am Heart J 1984; 107:1229–1234. National Fire Protection Association. NFPA Association 1582: Standard on Comprehensive Occupational Medical Program for Fire Departments. Quincy, MA: National Fire Protection Association; 2007. Kodama S, Saito K, Tanaka S, Maki M, Yachi Y, Asumi M, et al. Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis. JAMA 2009; 301:2024–2035. Baur DM, Leiba A, Christophi CA, Kales SN. Low fitness is associated with exercise abnormalities among asymptomatic firefighters. Occup Med (Lond) 2012; 62:566–569. Fagard RH. Exercise characteristics and the blood pressure response to dynamic physical training. Med Sci Sports Exerc 2001; 33 (6 Suppl): S484–S492. discussion S493–S494. Sharman JE, LaGerche A. Exercise blood pressure: clinical relevance and correct measurement. J Hum Hypertens 2014 [Epub ahead of print]. Barr D, Gregson W, Reilly T. The thermal ergonomics of firefighting reviewed. Appl Ergon 2010; 41:161–172. Singh JP, Larson MG, Manolio TA, O’Donnell CJ, Lauer M, Evans JC, Levy D. Blood pressure response during treadmill testing as a risk factor for newonset hypertension. The Framingham heart study. Circulation 1999; 99:1831–1836. Horn GP, Gutzmer S, Fahs CA, Petruzzello SJ, Goldstein E, Fahey GC, et al. Physiological recovery from firefighting activities in rehabilitation and beyond. Prehosp Emerg Care 2011; 15:214–225. Huang PH, Leu HB, Chen JW, Lin SJ. Heart rate recovery after exercise and endothelial function – two important factors to predict cardiovascular events. Prev Cardiol 2005; 8:167–70.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Clinical methods and pathophysiology
Blood pressure and heart rate responses in volunteer firefighters while wearing personal protective equipment Deborah L. Feairheller Background Hypertension, cardiovascular disease, and obesity are global health problems and are a large concern for firefighters. The leading cause of death among firefighters is cardiac-related; hence, it is important to understand how firefighter personal protective equipment (PPE) affects cardiovascular responses to different activities. Volunteer firefighters represent 70% of all firefighters and are an understudied population. To the best of our knowledge, this is the first study to report blood pressure (BP) responses in volunteer firefighters. Methods and results Thirty-six male, nonsmoking volunteer firefighters (27.8 ± 9.7 years) underwent two maximal treadmill tests within 2 weeks, one in regular gym clothes and one in PPE. We found that while wearing PPE, which weighs 54.2 ± 3.5 lbs, BP responses are exaggerated during work and in recovery. Systolic BP and heart rate were significantly (P < 0.05) higher at each submaximal stage and during active recovery of the PPE test compared with the regular clothing test (15–23 mmHg and 20–34 bpm higher, respectively). Test time and VO2 max were lower in the PPE test (P < 0.05).
Introduction Hypertension, cardiovascular disease, and obesity are global health problems [1,2]. Hypertension has a direct relationship with increased body weight and risk for cardiac incidents [3]. Firefighting is one of the most hazardous and dangerous jobs, with an inherently increased risk of death; many firefighters have hypertension, and the leading cause of death in firefighters is cardiac-related [4,5]. Research on male firefighters recently reported that the predictors of on-duty cardiac deaths include increased blood pressure (BP), previous heart disease, obesity, and smoking status [4,6]. BP awareness continues to be low, whereas hypertension rates continue to be high [2]. Hypertension control also remains a problem among both the general population and firefighters [1,7]. Supporting this, Soteriades et al. [7] reported that 74% of hypertensive firefighters did not have adequate control of their BP. Thus, it is important to increase the awareness of BP levels in firefighters, both at rest and under different work conditions. Environmental hazards require that firefighters wear personal protective equipment (PPE) which contains a self-contained breathing apparatus (SCBA). The SCBA provides a controlled environment of safe pressurized air through the use of a full facemask and a regulator system. 1359-5237 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Conclusion BP responses are exaggerated while wearing full fire protective gear and remain elevated during recovery. Awareness of how firefighting activities affect BP is important; so future studies should examine how the BP increase relates to resting BP levels, to PPE weight, and to the thermal effects of the PPE. Blood Press Monit 20:194–198 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Blood Pressure Monitoring 2015, 20:194–198 Keywords: blood pressure, cardiovascular health, exercise, firefighters, self-contained breathing apparatus The HEART (Hypertension and Endothelial function with Aerobic and Resistance Training) Laboratory, Department of Health & Exercise Physiology, Ursinus College, Collegeville, Pennsylvania, USA Correspondence to Deborah L. Feairheller, PhD, The HEART (Hypertension and Endothelial function with Aerobic and Resistance Training) Laboratory, Department of Health & Exercise Physiology, Ursinus College, 601 E. Main Street, Collegeville, PA 19426, USA Tel: + 1 6100 409 3256; e-mail: [email protected] Received 11 January 2015 Revised 4 March 2015 Accepted 10 March 2015
Firefighting, while wearing full PPE, imposes significant cardiovascular strain because of the heavy physical workload, weight of the SCBA, limited mobility, thermal effects, and impaired balance and visibility that heavy gear can cause [8–13]. Despite improvements in design and weight of both PPE and SCBA, evidence still suggests that the increased stress affects many cardiovascular variables; however, BP has not been examined. The cardiovascular effects of wearing PPE with SCBA have been tested in college male individuals and career firefighters, but limited research has been conducted on volunteer firefighters [14–17]. Tests have been performed in different PPE configurations, and all have reported that heart rate (HR) was higher and VO2 max was lower in the experimental group when compared with the a control group (regular gym clothing) [14–17]. Separate studies have also examined HR and thermal effects of firefighting under different temperature conditions [13]. Yet, none of these studies have reported BP responses. Importantly, participants in all of these studies had carried the SCBA but were not breathing through the SCBA regulator. During structural fire suppression or rescue work, firefighters wear their full PPE, as well as breathe through the SCBA. To the best of our knowledge, only two exercise studies have been performed where the DOI: 10.1097/MBP.0000000000000120
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Blood pressure responses in volunteer firefighters Feairheller 195
participants were asked to breathe through the SCBA regulator [18,19]. Both studies reported that the added resistance from the SCBA regulator may have contributed to a lower VO2max when compared with the control group, but neither reported BP responses. Currently, volunteer firefighters represent 70% of the total firefighting population, and thus are an important population to study [20]. The prevalence of cardiovascular risk factors, including elevated BP, is higher in firefighters than in the general population [2,21,22]. Considering the higher cardiovascular risk that firefighters face, the low levels of BP awareness, and the fact that research on BP of firefighters is extremely limited, the purposes of this study were to examine BP and HR responses to work (through the maximal-graded treadmill test) in volunteer firefighters while wearing full PPE + SCBA, as used during fire suppression activity.
Methods Participants
Forty-five volunteer firefighters from around the Philadelphia suburban area were recruited by word of mouth or contacted researchers after seeing media news articles [23]. Thirty-six were included in the analysis, because they met the inclusion criteria and completed both treadmill tests. Criteria for inclusion were: male volunteer firefighter, no prior cardiovascular incidents, no diagnosed heart disease or diabetes, nonsmoker, and completion of both treadmill tests within a 2-week period. Sex differences exist in rates of high BP and in response to exercise; hence, female firefighters were not included [24]. Each firefighter gave informed consent and completed a general health history form. The protocol was approved by the Ursinus College Institutional Review Board, and all procedures were in accordance with the ethical standards of the Helsinki Declaration. Study protocol
This was a single-group cross-over study. All enrolled firefighters underwent two maximal treadmill tests within a 2-week period, at the same time of day: one in regular gym clothes and sneakers (regular test), and one in full firefighter PPE (PPE test). Full firefighter PPE included boots, pants, a jacket, gloves, and a helmet, along with the SCBA air pack and face mask system. Firefighters were asked to breathe air through the SCBA regulator during the PPE test. During the PPE test, the right sleeve was turned inside out and tucked inside the jacket, so that exercise BP measurements could be taken. Before each test, body weight was measured in regular clothing (for regular test) and in full PPE + SCBA (for PPE test). Resting and exercise BP levels were measured according to published guidelines [2]. In brief, BP measurements were performed by auscultation with a mercury sphygmomanometer, the first and fifth Korotkoff sounds corresponding to systolic and diastolic
BP. The measurements were taken at the following time points: before exercise at rest, during exercise at the last minute of each stage, after exercise at 2 and 4 min during active cool down, and after exercise during a seated recovery. BP measurements were taken using a correct size arm cuff, with the arm supported at the same level as the heart. All BP measurements were taken by the same operator, using the same sphygmomanometer. Treadmill test
A maximal symptom-limited Bruce protocol exercise stress test was performed. BP and perceived exertion were measured at each stage. HR (Polar Electro Inc., Lake Success, New York) was monitored at each minute of exercise. ECG was monitored during the regular test (Nasiff CardioCard; Nasiff Associates Inc., New York, New York, USA). The treadmill test was terminated using criteria according to guidelines [25]. Postexercise BP and HR were monitored during active recovery (1.7 mph, 0% grade) at 2 and 4 min after test termination. Postexercise BP and HR were also measured at 6 min after test termination, while the firefighter was seated with his feet flat on the floor. VO2max levels were calculated using the Bruce protocol test time formula [26]. Statistical analyses
Significance was set at P less than 0.05. Data are expressed as mean ± SD. All statistical analyses were carried out using SPSS version 19.0 (SPSS Inc., Chicago, Illinois, USA). The distribution of all variables was examined using the Shapiro–Wilk test of normality. Repeated measures analysis of variance was carried out to examine whether any condition (i.e. PPE, regular) by time (i.e. stage BP, minute HR) interaction effect existed. Post-hoc within-group analysis was carried out using paired t-tests to compare values between timepoints. Between group analyses were carried out using independent t-tests to determine whether there were significant differences between the regular test group and the PPE test group at each timepoint. Pearson’s correlation was used to determine whether there were relationships between variables, and this was further examined by linear regression analysis. Data were also covaried for body weight, gear weight, age, maximum systolic BP, and VO2max.
Results Thirty-six male volunteer firefighters (27.8 ± 9.7 years) completed the study. Table 1 presents the participant characteristics. The average weight of the firefighting PPE was 54.2 ± 3.5 lbs. The volunteer firefighters had several cardiovascular risk factors, confirming what other studies have found [7,21]. The average BMI of the firefighters was 30.8 ± 6.3 kg/m2, with most participants being overweight (23%) or obese (44%), similar to other studies [21] The average resting BP of the firefighters was 129.4/75.1 mmHg, which is classified as prehypertension.
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Blood Pressure Monitoring 2015, Vol 20 No 4
Volunteer firefighter characteristics
None of the firefighters included in this study were on medication for BP. The volunteers had an average of 9.25 years of service, responded to 13.7 emergency calls a month, and attended 2.9 trainings a month. The National Fire Protection Association has established that the demands on the cardiovascular system require a fitness level of at least 12 metabolic equivalents (METs), which is the equivalent of a VO2max of 42 kg/ml/min [27]. The volunteer firefighters in our study reportedly exercised only 1.9 times per week and had an estimated average VO2max of 37.7 ± 7.2 ml/kg/min, which is below the National Fire Protection Association recommendations. Exercise test responses between personal protective equipment and regular tests
The physiological responses at maximum exercise are shown in Table 2. The total test time was significantly shorter for the PPE test (7.2 ± 0.8 min) compared with the regular test (10.7 ± 1.8 min, P < 0.05), and the estimated VO2max was lower for the PPE test (24.2 ± 2.7 ml/kg/min) compared with the regular test (37.8 ± 7.2 ml/kg/min). Systolic BP responses to exercise are shown in Fig. 1. Mauchley’s test of sphericity indicated that the assumption of sphericity had been violated [χ2(5) = 21.02, P < 0.01]; therefore, a Greenhouse–Geisser correction was used. There was a significant effect of condition on systolic BP (P = 0.000). Post-hoc pairwise comparisons revealed that systolic BP was significantly higher
∗ ∗
Re 2 m co in ve ry Re 4 m co in ve ry 6 Se m at in ed
M ax
2 ge
ge
St a
g
1
∗
St a
Data are presented as mean ± SD. DBP, diastolic blood pressure; PPE, personal protective equipment; SBP, systolic blood pressure; VO2, oxygen consumption.
FF: Reg FF: PPE
220 210 200 190 180 170 160 150 140 130 120 tin
Value 27.8 ± 9.7 70.6 ± 3.0 212.2 ± 41.6 30.8 ± 6.3 129.4 ± 9.7 75.1 ± 6.9 75.7 ± 12.5 54.2 ± 3.5 13.7 ± 6.1 2.9 ± 1.1 9.3 ± 9.4 1.9 ± 1.7 37.7 ± 7.2
Age Height (inches) Body weight (lb) BMI (kg/m2) Resting SBP (mmHg) Resting DBP (mmHg) Resting heart rate (bpm) Weight of PPE (lb) Emergency calls responded to/month Trainings attended/month Years in service Times exercise/week VO2max (ml/kg/min)
Re s
Variable (N = 36)
Fig. 1
Systolic blood pressure (mmHg)
Table 1
Comparison of systolic blood pressure responses at each stage of a Bruce protocol exercise test, between regular clothing (solid bars) and full firefighter personal protective equipment (PPE, open bars), during active recovery (1.7 mph, 0%), measured at 2 and 4 min during recovery, and at 6 min after exercise while seated. *Significance: P < 0.05 between groups. FF, firefighter; PPE, personal protective equipment.
(15–23 mmHg higher) at each submaximal stage of the PPE test compared with the regular test (P < 0.05). In addition, systolic BP at 2 min active recovery was higher during the PPE test compared with the regular test (P < 0.05). HR responses to exercise are shown in Fig. 2. There was a significant effect of condition on HR (P = 0.000). Posthoc pairwise comparisons revealed that HR was significantly higher (20–34 bpm higher) at each submaximal minute of the PPE test compared with the regular test (P < 0.05). In addition, HR at 2 min and 4 min active recovery was higher during the PPE test compared with the regular test (P < 0.05). Fig. 2
FF: Reg FF: PPE
190 Heart rate (bpm)
196
170 150 ∗
130
∗
∗
∗
∗
∗ ∗
∗ ∗ ∗
110 90
Data are expressed as mean ± SD. DBP, diastolic blood pressure; PPE, personal protective equipment; SBP, systolic blood pressure; VO2, oxygen consumption. *Significance: P < 0.05 between groups.
8 Re Ma in cov x R e 6 eco ry m in ver Se y at ed
7
6
5
4
3
2
in
m
216.7 ± 11.6 79.8 ± 6.3 185.8 ± 8.8 24.2 ± 2.7* 7.2 ± 0.8*
m
PPE test
211.4 ± 14.6 78.8 ± 6.1 191.5 ± 25.2 37.8 ± 7.2 10.7 ± 1.8
4
Regular test
SBP max (mmHg) DBP max (mmHg) Heart rate max (mmHg) VO2max (ml/kg/min) Total exercise time (min)
2
Variable (N = 36)
Re
st in
g
Responses to exercise test
1
70 Table 2
Comparison of heart rate responses during each minute of a Bruce protocol exercise test, between regular clothing (solid bars) and full firefighter personal protective equipment (PPE, open bars), during active recovery (1.7 mph, 0%), measured at 2 and 4 min, and at 6 min after exercise while seated. *Significance: P < 0.05 between groups. FF, firefighter; PPE, personal protective equipment.
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Blood pressure responses in volunteer firefighters Feairheller 197
We found no differences in maximal BP or HR levels.
Discussion The main finding of this study is that volunteer firefighters have exaggerated systolic BP and HR levels during each stage of incremental exercise, as well as during recovery time, while wearing full PPE and SCBA. To date, most studies on firefighters have included career firefighters or mixed populations of career and volunteer firefighters, and the studies have included smokers. In a population of volunteer firefighters, we confirmed what other studies have reported; firefighters may have increased cardiovascular risk [4,5,7]. The volunteer firefighters in our study were inactive, had low fitness levels, were overweight or obese, and had prehypertension. Research consistently shows that low cardiorespiratory fitness is related to cardiovascular events, hypertension, and mortality [28,29]. Furthermore, it is known that BP responses to exercise differ for normotensive compared with hypertensive individuals [2,30]. To the best of our knowledge, this is the first study to report BP levels in firefighters during activity. In general, physical activity leads to an increase in cardiac output to perfuse the working muscle beds [31]. Sympathetic activity increases, leading to a rise in systolic BP and HR. The normal systolic BP increase for men at stage 1 of the Bruce protocol is 20–30 mmHg and at the maximal stage is 50–60 mmHg, compared with resting levels [31]. In our study, for firefighters wearing PPE, we found that systolic BP increased from resting levels by 35 mmHg at stage 1 and by 87 mmHg at the maximal stage. Considering that firefighters work in extremely stressful environments, with high physical demands, while wearing heavy, thickly insulated and fully encapsulating clothing, we would expect that BP and HR would increase more than under the baseline condition [32]. However, the relationship between the magnitude of the BP elevation and different gear weights or configurations needs to be elucidated. No other study on firefighters has measured BP during activity; thus, this is the first step toward understanding BP responses to work while wearing PPE. Our results suggest that either the weight or the thermal insulation effects of the PPE aggravate the BP responses to exercise. We also found that recovery systolic BP and recovery HR were exaggerated in firefighters wearing PPE. Once activity stops, systolic BP is expected to decline rapidly after exercise, and recovery BP responses are thought to provide prognostic information. The proper timeline needed for recovery from firefighting activities has yet to be established. In the general population, elevated postexercise systolic BP has been related to an increased risk for future hypertension or myocardial infarction [33]. A 3 min SBP ratio (SBP at 3 min after exercise/SBP at max) over 0.9 has been used to evaluate the risk for heart disease in prior studies [33]. None of the firefighters in
our study had a ratio over 0.9 (data not shown), which suggests a relative lack of overt heart disease in our population. In 2011, Horn et al. [34] reported that the recovery timeline from firefighting activities may be significantly longer than the typical 10–15 min rehabilitation that firefighters are supposed to follow. In their study, BP was measured before and after firefighting activity, after rehabilitation (15 min after exercise), and every 30 min for 2 h, in both career and volunteer firefighters. They found that systolic BP dropped during rehabilitation (measured at 15 min after exercise) [34]. In our study, under the PPE condition, firefighters had significantly higher systolic BP during active recovery compared with firefighters in regular clothing, suggesting that the PPE aggravates BP. Recent studies have reported strong relationships between a slower HR recovery and cardiovascular disease [35]. An exaggerated HR level during recovery could be due to peripheral resistance, metabolic disorder, or other vasoregulatory causes. Smith et al. [9] reported recovery HR levels in a mixed population of career and volunteer firefighters. They found that HR was still elevated at 8 and 16 min after firefighting activity compared with resting levels. Horn et al. [34] reported that HR remained elevated for 70–100 min after firefighting drills. Both studies suggest that when active fire suppression or heavy firefighting work is in progress, rehabilitation times should be observed. Our study is the first to report active recovery and immediate postexercise recovery seated BP and HR levels. Future studies are needed to understand how different conditions affect cardiovascular recovery in firefighting. We recognize that our study has several limitations. For the PPE test, the bunker coat sleeve was turned inside out; hence, the true BP response to thermal conditions may not have been measured, but this study was designed to examine the effects of weight (PPE + SCBA) and increased workload (treadmill stress test) on BP responses. The thermal effects on BP can be addressed in a future study. In addition, our study included only male, nonsmoking, volunteer firefighters; hence, results cannot be generalized to the entire firefighter population. Future studies can examine BP responses in other populations. Conclusion
This is the first study to report BP responses in volunteer firefighters to an exercise stress test. We found that while wearing full PPE and SCBA, the same configuration of protective gear used during fire suppression and rescue activities, BP at each submaximal workload was significantly higher compared with BP in regular gym clothes. These data suggest the need for further research on BP responses to different workloads in volunteer firefighters. High BP is a chronic health problem in society. Firefighters are at an increased risk for high BP,
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198 Blood Pressure Monitoring 2015, Vol 20 No 4
and those with elevated BP may not have it under control. The leading cause of firefighter fatalities remains cardiovascular; hence, research needs to understand how the protective gear that firefighters wear affects their cardiovascular responses, in particular, BP.
Acknowledgements The authors thank the volunteer firefighters for their participation in the study: fire stations in Pennsylvania included Collegeville, Trappe, Upper Frederick, and Lower Providence from Montgomery County; Reading from Berks County; and East Brandywine, Thorndale, and Oxford from Chester County. They also thank Matthew Generotti for help with the initial research design. Further, they thank the HEART lab research students who participated in data collection, including: Kristin Aichele, Joy Oakman, Avery Perez, Christina Cromwell, Mike Neal, and Jessica Lenzo.
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Conflicts of interest
There are no conflicts of interest.
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