Features Health and wellness Hot topics
WellBeing: August 2010

With the advent of new health monitoring technology, researchers are better able to explain why firefighters are more susceptible to heart attack than the general public. The leading cause of firefighter deaths continues to be heart attack. NIOSH estimates that there are an additional 1,000 on-duty non-fatal heart attacks for every cardiac death in North America. Investigations reveal that almost all firefighters who died of heart attack had underlying heart disease. Heart disease is an umbrella term for diseases that affect the heart, including coronary artery disease, conduction system malfunction, heart failure, valvular conditions and cardiomyopathies.

Most heart disease is a result of coronary artery disease or CAD.In firefighters, CAD may be due to a combination of personal and workplace factors. The personal factors are well known: age, gender, family history, diabetes, hypertension, smoking, high blood cholesterol, obesity and lack of exercise. NIOSH reports several workplace factors including exposure to smoke, diesel exhaust emissions, noise and shift work.

The presence of risk factors or even CAD alone, however, does not explain the high rate of heart attack death in firefighters, especially since the fatal heart attacks among firefighters have occurred in individuals who are younger than the average for the general public.

Researchers believe the trigger mechanism for heart attack may be attributed to both physical and emotional response to fire operations. With the advent of new technology such as wireless heart rate, respiratory rate, body position and skin temperature monitoring devices, researchers are better equipped to analyze the physiological response to fire operations. One recent study conducted by researchers at Indiana University used this technology to analyze the physiological stress on firefighters before, during and after actual fire suppression incidents.

The study found that cardiovascular and respiratory stress begins during the initial response to the station alarm. Increases in heart and ventilation rate in response to the alarm are induced by an adrenalin release that gives us our fight or flight response.  Explained by Pavlov-like conditioning, the increased ventilation and heart rate occur even before movement begins. Secondly, as the firefighter begins to move toward an apparatus, heart and ventilation rate increase even further. The study found that heart rates typically rise to 80 per cent of predicted heart rate maximum before lowering as the firefighter settles into the rig. 

The heart and ventilation rate during a call vary depending on the type and duration of the incident; the more serious the incident, the greater the physiological response. Scientists already know that all physical activity raises body temperature and causes the release of many hormones such as adrenalin. They didn’t realize how much of a role adrenalin actually plays in fire fighting. Adrenalin raises the heart rate and blood pressure and increases ventilation. The higher the physical demand or emotional stress, the greater the rise in temperature as well as the amount of hormone released.

During one rescue operation documented in the study, four firefighters rescued multiple victims (children) from a second floor bedroom. All four firefighters worked at or above their maximum predicted heart rate for more than 25 continuous minutes. This feat is physiologically impossible without the presence of adrenalin. The workload placed on the hearts of these firefighters was enormous. Fortunately, all four firefighters involved in this incident were in exceptionally good shape and did not possess underlying CAD.  The firefighters all survived the incident; however, the outcome may have been very different had one of them possessed an underlying cardiovascular issue.

The effect from adrenalin does not disappear when physical activity stops or the emotional stimulus subsides. Time is required to metabolize adrenalin and dissipate body heat and therefore stress effects tend to linger. The four firefighters mentioned above had sustained elevated heart rates for much longer than the duration of the incident. In fact, three hours afterwards, their heart rates remained in excess of 100 beats per minute. Essentially, the physical and emotional triggers for heart attack stay with firefighters for some time after an incident.

This new research clearly demonstrates the magnitude of cardiovascular stress placed on working firefighters and indicates that firefighting activity can be a trigger for a cardiac event, especially in individuals with underlying CAD. The Indiana study emphasizes the need for physical fitness coupled with a comprehensive medical screening program. The authors conclude that, without good fitness and medical screening, cardiac death may be inevitable in firefighters with cardiovascular disease.

Ian Crosby is in his 17th year with the Calgary Fire Department and serves as its wellness and fitness co-ordinator. Crosby developed the department’s Wellness Centre, which opened February 2005. He is a member of the IAFF/IAFC/ACE Peer Fitness Trainer (PFT) Oversight Committee and an instructor for the PFT certification program. E-mail him at Ian.Crosby@calgary.ca