Emergency Incident Rehabilitation: Resource Document to the Position Statement of the National Association of EMS Physicians

Abstract

Position Statement: Emergency Incident Rehabilitation

The National Association of EMS Physicians® believes that:

• Emergency operations and training conducted while wearing protective clothing and respirators is physiologically and cognitively demanding.

• The heat stress and fatigue created by working in protective clothing and respirators creates additional risk of illness/injury for the public safety provider.

• Emergency incident rehabilitation provides a structured rest period for rehydration and correction of abnormal body core temperature following work in protective clothing and respirators.

• Emergency incident rehab should be conducted at incidents (e.g. fireground, hazardous materials, and heavy rescue emergencies) and trainings involving activities that may lead to exceeding safe levels of physical and mental exertion.

• Emergency incident rehabilitation is incident care, not fitness for duty, and meant to reduce physiologic strain and prepare the responder to return to duty at the current incident and for the remainder of the shift.

• EMS should play a role in emergency incident rehabilitation with providers trained to understand the physiologic response of healthy individuals to environmental, exertional, and cognitive stress and implement appropriate mitigation strategies.

• An appropriately qualified physician should have oversight over the creation and implementation of emergency incident rehabilitation protocols and may be separate from the roles and responsibilities of the occupational medicine physician.

• There are no peer-reviewed data related to cold weather rehabilitation. Future studies should address this limitation to the literature.

Key words::

• Firefighter
• heat stress
• recovery
• operational readiness

Introduction

The National Association of EMS Physicians (NAEMSP) has published a new position paper on “Emergency Incident Rehabilitation.” This paper is the resource document for that position and will guide practitioners in their understanding and implementation of this new position statement.

The duties incumbent upon structural firefighters and rescue personnel (e.g., fire suppression, hazardous materials response, heavy rescue) are dangerous with an estimated 80,000 firefighters being injured in the line of duty each year.¹ Most emergency functions require the firefighter or rescue worker to deploy in a variety of protective clothing. While each of these protective garment combinations serves a different purpose, every combination creates an uncompensable heat stress situation that typically overwhelms the thermoregulatory system resulting in hyperthermia and hypohydration.^2–7 The physical strain associated with emergency duties results in fatigue, psychological stress, and cognitive impairment.^7–10 This combination of symptoms predisposes the emergency responder to injury.

Emergency incident rehabilitation refers to structured and unstructured rest periods that provide the responder an opportunity to recover, rehydrate, and reduce the core body temperature.¹¹ EMS providers are often called upon to implement rehab operations. It is important, therefore, that EMS providers and medical directors have a fundamental understanding of the normal physiologic response to environmental, exertional, and cognitive stress and the benefits and limitations of the mitigation strategies that can be brought to an incident. The vast majority of studies related to emergency incident rehabilitation in structural firefighters focuses on heat stress mitigation and correction of hypohydration. Cold weather operations are required in many parts of the world. However, there are no peer-reviewed data related to cold weather rehabilitation. Best practices for these incidents must be derived from other fields until these data become available.

Assessment of the Literature

Structural firefighting is the focus of the position statement and resource document. Wildland firefighting and tactical operations present a unique set of challenges that should be considered based on the literature available in those areas. We performed a comprehensive review of the literature pertaining to heat stress among emergency responders, the role of protective equipment on physiologic stress, and work:rest ratios among emergency responders. We also examined the literature for studies examining rehydration and cooling techniques among emergency responders. To our knowledge, there are no clinical trials or longitudinal studies pertaining to emergency incident rehabilitation. There is a substantial body of literature of laboratory and field studies examining heat stress among emergency responders and rehabilitation techniques.

Background

The physiologic demands of fire suppression and exertion in protective clothing are well documented. Simply wearing the thermal protective clothing and self-contained breathing apparatus associated with fire suppression lowers an individual's maximum cardiorespiratory capacity (VO_2max).^12,13 The recommendations for minimum firefighter fitness range from 10 metabolic equivalents (METS; 35 mL/kg/min VO_2max) to 14 METS (48 mL/kg/min).^14–16 These studies, however, are more than 20 years old and could not appreciate the advancements in protective clothing that have resulted in greater physical loads so the fitness level required to minimize cardiovascular strain may be higher. A large proportion of firefighters are obese, physically inactive, and do not meet the fitness recommendations.^17–19 Low cardiorespiratory fitness results in firefighters achieving maximum heart rate earlier in a bout of work and longer recovery periods are required before less fit firefighters can safely return to work.² It is critical, therefore, that firefighters be adequately monitored and provided an opportunity to rest at regular intervals during an incident in order to sustain operation.

Lab and field studies of firefighters working in protective clothing have shown that near maximal heart rates are achieved in as little as 20 minutes, and in some cases supramaximal, depending on the type of exertion being performed.^{2,4,9,20–24} Bulky garments essentially ablate evaporative cooling. Core body temperature rises rapidly exceeding 38.0°C in 20 minutes and often approaches 39.5°C in 45–50 minutes.^2,4,22,25 The rapid rise in body temperature evokes a strong sweating response that results in firefighters losing up on one kilogram of body mass in the first 20 minutes of fire suppression.² This triad of symptoms (tachycardia, hyperthermia, hypohydration) must be addressed during the emergency incident rehab period to allow the firefighter to safely return to work and after the incident to ensure the firefighter is prepared for subsequent emergency calls.

Other signs and symptoms have been reported in firefighters following exertion in protective garments. Platelet activation accompanies exertional heat stress in firefighters.^26,27 One study of aspirin therapy in firefighters reported that neither daily aspirin therapy (81 mg) nor single dose aspirin (325 mg) taken after heat stress could entirely prevent the platelet activation.²⁶ Coincident with platelet activation, coagulation and fibrinolysis are concomitantly upregulated in firefighters.^25,28 Various aspects of coagulation remain elevated for an unknown time interval following emergency incident rehabilitation leaving the firefighter in a procoagulant state.²⁵ While this does not endanger firefighters per se, it could worsen a myocardial infarction suffered during or in the period following fire suppression.

Cognitive fatigue has been reported in healthy subject after significant dehydration.²⁹ The data among firefighters are less clear. It has been reported that healthy individuals do not display changes in short-term memory, sustained and divided attention, or reaction time immediately following exertion but subtle changes in reaction time have been detected one hour following exertion.⁸

Goals of Emergency Incident Rehab

The traditional goals of emergency incident rehabilitation are relief from environmental conditions, correcting abnormal body temperature, rest, rehydration, and providing nutrition during longer duration incidents. Historically, emergency incident rehabilitation was presented as a formalized process requiring some number of personnel to establish a sector within the incident and assemble equipment for cooling, rehydration, and medical monitoring.¹¹ While the structured form of emergency incident rehabilitation is common, unstructured (e.g., providing bottled water during short break periods, shelter in the shade) rehab can be useful at smaller incidents where a rehab sector will not be established or early in an incident before the rehab resources have arrived. The time required for full rehydration and physiologic recovery may extend hours beyond the incident. Studies have shown that mild tachycardia and hyperthermia may persist for an hour or more after a single bout of fire suppression or after 50 minutes of moderate exertion in thermal protective clothing.^2,8 Firefighters may need additional rehydration and rest after returning from an incident to assure readiness at a subsequent incident. Optimal treatment from these insults has not been defined.

A structured rehabilitation sector provides an opportunity for vital sign monitoring. The most commonly monitored vital signs are heart rate, blood pressure, respiration, and pulse oximetry. Heart rate recovery following fire suppression is influenced by baseline fitness. Both the fittest and least fit firefighters can achieve heart rates below 100 bpm when compared to moderately fit (10–12 MET) firefighters.² The influence of high cardiorespiratory fitness on recovery is well documented but the significance of a rapid reduction of heart rate in less fit firefighters is still unclear. It is likely that unfit firefighters cannot achieve high heart rates during the heavy exertion associated with fire suppression providing the appearance of rapid recovery. Moderately fit firefighters are more likely to achieve near maximal heart rates but are not fit enough to recover quickly. There are no evidence-based recommendations for what heart rate should be observed before a firefighter returns to an incident. Persistent tachycardia may be a sign of more profound dehydration or medical issues but 45% of moderately fit firefighters did not achieve a heart rate below 100 bpm 30 minutes after entering the rehab sector in one study.² Considerable clinical judgment balancing the needs of the incident with the health of the firefighter is required.

EMS providers are not routinely taught how to interpret blood pressure following exertion. Blood pressure rises during exertion and rapidly falls during the initial recovery period. Post exercise hypotension is well-documented following heavy exercise and may be more prominent in hypertensive individuals.³⁰ This has also been documented in firefighters after a single 18-minute bout of activity in a heated building.³¹ EMS providers working in the rehab sector should be vigilant for both hypertension and symptomatic hypotension. Normally hypertensive firefighters with normal blood pressure following fire suppression may be displaying a relative hypotension.

Respiratory rate and pulse oximetry are relatively easy to measure but may have limited prognostic value in healthy individuals recovering from exertional heat stress. Routinely monitoring firefighters for carbon monoxide (CO) exposure is theoretically beneficial but it has not been conclusively demonstrated. CO levels are high during structure fires and can remain elevated in the period following fire suppression.^32,33 Failing to use respiratory protection during fire suppression leads to substantial CO accumulation.³⁴ CO exposure and high carboxyhemoglobin levels in the post fire suppression period, commonly referred to as overhaul, has not been definitively shown in the literature. One administrative study reported low CO levels in firefighters measured during the rehab period by CO-oximetry.³⁵ This may have been a function of that particular fire department's policy to extensively ventilate a structure after fire suppression but before beginning active overhaul.

It is important to note that no study has conclusively demonstrated the value of monitoring vital signs in the rehab sector and there are no evidence-based recommendations for a vital sign threshold indicating that it is safe to return to the incident. It is likely that the most valuable aspect of vital sign monitoring during rehab is documenting appropriate trends during recovery (e.g., declining heart rate) and identifying extremes of heart rate or blood pressure, which may indicate underlying illness. The need for routine medical monitoring in the rehab sector is at the discretion of the medical director except in situations where required by law (e.g., OSHA requirements at hazardous materials incidents).

Approaches

The general principles of emergency incident rehabilitation include providing a safe place for the firefighter to rest and remove protective garments. EMS providers should observe the firefighters for signs of exertional heat illness during warm weather and cold conditions (e.g., frost nip, frost bite) during cold weather operations. When possible, easily absorbed forms of nutrition should be provided at prolonged incidents or at incidents spanning a mealtime. Specific practices for modulating work/rest cycles, providing rehydration, and correcting body temperature are discussed in the following section.

Work/rest Cycles

NFPA 1584 outlines a recommended rehabilitation process for fireground operations and requires that rehabilitation and rest be written into each department's standard operating guidelines (SOG). The recommendations call for periods of structured rehabilitation that can be adjusted based on the duration of the work interval, the operational demands of the incident, and the fitness of the firefighter. Although establishing a rehabilitation sector is at the discretion of the incident commander, a common guideline used by many U.S. fire departments is to rotate firefighters through a rehab sector following activities during which two 30-minute self-contained breathing apparatus (SCBA) cylinders were used, (about 45 minutes total time). This is commonly referred to as the “two-cylinder rule.” Additional recommendations for entering structured rehab include consuming a single 45 or 60-minute SCBA cylinder and 40-minutes of intense work without SCBA. These guidelines, however, are consensus derived and the crew supervisor or company officer may adjust the time spent in the rehabilitation sector based on the operations.

Recovery has a variety of definitions but is often defined in the context of emergency incident rehabilitation as a return of function to normal levels without any adverse side effects from the current or previous activity. However, due to the limited physiological monitoring available on the fireground and the subjective nature of “normal,” some firefighters will return to work before they have fully recovered from the previous bout of work. Both laboratory and field studies have shown that 20-30 minutes of structured rehabilitation is not sufficient to restore vital signs to baseline levels but may be enough to safely continue fireground activities.^2,4,22,36 Providing longer rest and relief periods may require the incident commander to summon additional crews to contribute to the incident.

It should be noted that there is little objective evidence to support the NFPA 1584 recommendations on work:rest ratios. The lack of data in the literature means many recommendations are consensus derived. Additional research is needed to determine the validity of these recommendations and/or to determine the optimal work:rest ratio during fire suppression and rescue.

Laboratory studies of work under uncompensable heat stress conditions: Intermittent work cycles have been reported to cause greater heat strain when compared to continuous bouts of work under uncompensable heat stress conditions. Endurance time was significantly less, while core body temperature and the rate of rise in temperature was significantly greater.³⁷ A series of fireground tasks based on the Fire Service Candidate Physical Ability Test (CPAT) performed under uncompensable heat stress conditions (40°C; 45% relative humidity (RH)) resulted in greater than 1.5°C increase in core temperature and an average completion time that was less than 16 minutes slower than when the same test was performed under compensable conditions (18°C; 45% RH). Core temperatures will continue to rise after work ends creating additional heat load that must be dissipated during rehab.^2,38

As shown previously, heart rates are near the age predicted maximal and core body temperature rises rapidly after fire training evolutions. Nearly one kilogram of body mass is lost due to excessive sweating in a single 15-20 minute live fire training evolution. Even thirty minutes of aggressive rehabilitation may not sufficient to elicit a full recovery regardless of cooling modality calling into question the “two cylinder rule” that is traditionally used by fire departments as the time course for work and rehabilitation.^4,22

Establishing work/rest ratios and recommendations: Work in chemical or thermal protective clothing has been reported to add heat strain to the wearer equivalent to adding approximately 4–11°C WBGT.^39–43 Based on these findings, Hanson developed a draft British Standard for workers wearing PPE, which is based on the conditions of the thermal environment, wet bulb globe temperature (WBGT), intensity of work, and the level of insulation provided by the PPE.³⁹ Based on a correction factor of -10°C WBGT, a work/rest ratio of 1:3 was recommended. However, after field-testing, BS EN 12515 was updated to indicate that a 30-minute work: 30-minute rest schedule should be followed during work in PPE. Testing of this ratio demonstrated that no aural temperatures exceeded 38°C during work.³⁹ However, this method of estimating core temperature during heat stress is unreliable during exertional heat stress.⁴⁴

Selkirk and McLellan examined the effects of four different workloads (very light = 2.5 km/hr, 0% grade; light = 4.5 km/hr, 0% grade; moderate = 4.5 km/hr, 2.5% grade; heavy = 4.8 km/hr, 5% grade) under three different environmental conditions (25°C, 30°C, 35°C; 50% RH) on core body temperature and performance.⁴⁵ The authors recommend that light work at 25°C could be safely performed for four 30-minute cylinder bouts (up to 120 minutes); while heavy work could be sustained for two cylinders (up to 60 minutes). For conditions exceeding 30°C, light work should not exceed 60 minutes with heavy work limited to only 30 minutes of work. These recommendations are based on safety cut-off points of 39.0°C for core body temperature and 95% of maximum heart rate for greater than three minutes. These recommendations do not take into consideration the fitness levels of firefighters nor do they establish recommendations for work times when using 45 or 60 minute SCBA cylinders. However, this is the only publication to date to make a recommendation for work durations based on empirical evidence.

The prevalence of overweight and obesity in both the career and volunteer fire service is high, ranging from 73-88%.^18,46,47 In addition, over 25% of firefighters do not meet the 12.0 METs minimum exercise threshold required to safely perform their duties.^46,47 Considering the physical requirements that a firefighter needs to possess and the health consequences of obesity, it seems intuitive that more investigation needs to be made into establishing work/rest cycles not only in relation to environmental conditions and protective clothing/equipment load, but also to understand how work/rest cycles should be adjusted in relation to a firefighter's fitness, body composition, and cardiovascular disease risk factors.

Rehydration

Euhydration is required to optimize performance. Firefighters participating in a 20 minute training fire (heavy work) or 50 minutes of treadmill walking in a hot room (moderate intensity work) lose 750–1000 mL of body mass to sweating.^2,4,8,22 Similar sweat losses can occur after treadmill walking in chemical protective clothing.³ As firefighters often report for duty mildly hypohydrated, the additional sweat losses can exceed 2% of body mass which reduces the effectiveness of thermoregulatory mechanisms.³¹ The resulting hypohydration increases heart rate and blood pressure to maintain blood flow to working skeletal muscle and the skin.

The type of fluid provided during the typical rehab period does not alter the rate of vital sign recovery or performance on a subsequent bout of work.²² Euhydrated subjects performed up to 50 minutes of treadmill exercise in a hot room while wearing thermal protective clothing and self-contained breathing apparatus. At the end of this work period, the subjects removed the protective garment and were provided 20 minutes of seated recovery. During this interval, the subject was randomly assigned to receive plain water, sport drink, or 37°C intravenous normal saline. In each case, the volume of fluid provided was equal to the mass lost during the exercise period. The type fluid did not affect heart rate recovery, reduction in core body temperature, or the duration of work performed in a subsequent bout. There may be benefits to providing carbohydrate-containing beverages in the rehab sector under certain circumstances. The American College of Sports Medicine position stand on exercise and fluid replacement states “consumption of normal meals and beverages will restore euhydration. Individuals needing rapid and complete recovery from excessive dehydration can drink ∼1.5 L of fluid for each kilogram of body weight lost. Consuming beverages and snacks with sodium will help expedite rapid and complete recovery by stimulating thirst and fluid retention”.⁴⁸ Therefore, it may be advantageous to provide carbohydrate containing beverages at longer duration emergency incidents but there are no direct data for this in emergency incident rehabilitation.

Cooling

A rise in core body temperature of 0.5–1.0°C after training fires have been commonly reported.^2,25 Larger rises in temperature may occur after prolonged bouts of activity in protective clothing.²¹ Additional elevations in core temperature occur after exertion ends due to the high workload and increased metabolism associated with fire suppression.^4,22,25 A variety of field cooling devices and techniques are available to first responders.⁴⁹ All of these techniques can be broadly classified as passive or active. Passive cooling is defined as allowing the human body to thermoregulate to the environment without augmenting convective or conductive cooling. Evaporation of sweat is the most effective form of passive cooling for heat stress individuals. Passive cooling can be as effective as active cooling when conditions favor sweat evaporation.^2,4 These conditions require the firefighter to remove as many protective garments as possible (minimally the coat, helmet, hood, and gloves) and be seated in a cool, low-humidity environment. Simply opening the turnout coat is not sufficient.⁵⁰ Even a minimal barrier such as long shirtsleeves can inhibit effective cooling.²

Active cooling are those devices or techniques that enhance convective or conductive cooling. The most common device available to the fire service is the electric or gas powered fan. These fans are equally effective as other devices and passive cooling in cool, low-humidity condition but are of limited value when used for rehab in hot humid environments.^4,45 If deployed, fans should be used to cool individuals and not the entire rehab sector. Limited cooling will be achieved if one fan is positioned to blow across multiple individuals. In extremely hot conditions (when ambient temperature significantly exceeds skin temperature), a fan blowing hot air across an already hyperthermic firefighter may actually impeded cooling.

Conductive cooling devices are commonly marketed to the fire service and typically transfer heat from the firefighter by placing the extremities into water which cools the blood in the superficial veins as it returns to the body core. A common variation of this technique is to have the firefighter grip a cool piece of metal with an exposed hand. Both techniques are equally effective and not superior to passive cooling in a cool, low-humidity environment.^4,51 One lab study has demonstrated that forearm and hand immersion is effective at cooling firefighters and extending work time when rehab is conducted in a hot humid environment.⁴⁵ However, the water container used in that study was much larger than commercially available devices. A simple and cost effective method to provide greater water volume for heat sinks is to deploy plastic five gallon buckets in the rehab sector. A subsequent field study also reported that forearm immersion cooling was superior to passive cooling when rehabilitation was conducted in hot environmental conditions.²⁵

Multiple studies have reported various degrees of success when using liquid-perfused cooling vests or vests embedded with phase change material for cooling during or following work in protective clothing.^52–55 Lab and field studies among firefighters have shown that an ice-water perfused cooling vest is as effective as other active cooling techniques but presents technical challenges and considerable costs when deploying the device on the fireground.^2,4

While choosing an effective cooling technique that is not cost-prohibitive is important, knowing when to deploy an active cooling technique is equally important. All fires are hot but not all fires occur on hot days. In many cases, simply removing protective clothing and resting in a cool, non-humid environment will be as effective as an active cooling technique. The definitions for “cool” and “low-humidity” have not been defined but studies failing to find an advantage for active cooling have typically been conducted in a laboratory at room temperature (22–24°C) and these can be used as guidelines. Lower ambient temperatures with high humidity or warmer temperatures with low humidity may be less favorable. It is worth noting that an optimal environment can be created on the fireground by utilizing air-conditioned vehicles (e.g., fire apparatus, busses) or nearby structures.

Summary

Public safety operations, particularly interior fire suppression is physiologically demanding and similar in some ways to sport and athletics. The environment can be dangerous and the protective equipment creates a significant barrier to thermoregulation resulting in hypohydration, hyperthermia, and fatigue.

Corrective measures have been investigated in both laboratory and field settings. In general, rehydration to match sweat losses may not be possible at the incident and public safety personnel should have an appreciation for the need to maintain hydration status during a shift. Providing sufficient time and opportunity to reduce body temperature enhances firefighter safety. Active cooling devices, however, may not be needed in every situation. Full recovery of baseline vital signs is not possible in the 20–30 minute interval allotted for emergency incident rehabilitation and firefighter fitness may alter the recovery timeline. At this time, there are not sufficient data to recommend a work to rest ratio for various situations and a minimal amount is known about many other physiologic derangements following exertional heat stress in firefighters.