Cold water can quickly wear down even highly fit individuals.
BY ANDREA ZAFERES AND WALT “BUTCH” HENDRICK
What is cold? We lose body heat in 80°F water at the same rate as in 42°F air!1 If you don’t picture yourself comfortable working outdoors in your underwear in 42°F air, then you should not consider working in 80°F water without proper personal protective equipment (PPE). In addition to taking care of themselves, rescuers at winter water operations should provide optimal care to immersion hypothermia patients, especially after removing them from the water. Such patients face additional challenges from the effects of cold during the preparation and transport phases.
Most people define hypothermia as “the body’s inability to maintain normal core temperature,” whereas the medical definition of hypothermia is a body core temperature of less than 95°F. A person using the medical definition might infer that a decrease in body core temperature short of 3°F is not a serious problem, as it does not constitute hypothermia. This is incorrect!
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The effects of cold and feeling cold can result in physical, mental, and even emotional stress well before medically-defined hypothermia occurs. For the purposes of this article, “cold stress” is defined as the direct or indirect effects of heat loss not defined by a specific core temperature loss.
Personnel who simply feel cold, regardless of core temperature loss, are more likely to shortcut standards, use poor judgment, and rush. A rescue tender may improperly install a harness on an ice rescue technician, and as a result the technician’s breathing is restricted 300 feet from shore.
Heat loss from extremities, rather than the core, can cause life-threatening problems. For example, a diver may be unable to release his weight belt to save himself because of cold hands. A tender without any core temperature loss might have such cold hands, because of inadequately insulated gloves, that he is unable to hold a tether line effectively, help rescuers with their equipment, or handle a patient without causing that person further injury.
Victims, even after removal from water, may suffer additional cold-related problems because of exposure to the weather, cold equipment, and wet clothing. Rescuers should keep this in mind in planning and training for winter water rescue operations.
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Let us examine cold stress and hypothermia a little more closely. Rennie presents a useful thermoregulatory model of the body.2 He considers the body as a thermodynamic engine with a liquid core surrounded by a musculoskeletal framework, bound with a layer of fat. Fat can be considered to have a constant thermal conductance-it provides a specific layer of insulated protection. Muscle tissue, on the other hand, can change how much heat we lose by changing the amount of fluid, namely blood, that is brought to our exterior from our core. Blood is what brings warmth from our core to our exterior, so if blood is transferred away from the core, the exterior temperature will increase and more heat will be lost to the cold environment. The harder we work, the more “vascular perfusion” of blood to our muscles, with the result that we lose more heat.
When the body can no longer stabilize its temperature, then we need to shiver or exercise to increase heat production. “Exercise produces metabolic heat at a rate of about three watts per watt of mechanical power.”3 But exercise can increase heat loss by convection, because of the body’s movement through the water medium it is immersed in and by vascular perfusion. If heat production exceeds heat loss, then the body can stabilize its temperature in cold environments. But sadly, without a proper exposure suit, heat loss almost always exceeds heat production during immersion in water. Experiments in water-filled tanks found that physical activity, including shivering, leads to a faster rate of heat loss than does remaining still.4,5
HEAT LOSS PROCESSES
The human body can lose body heat through conduction, convection, evaporation, and radiation. One does not need to be immersed in cold water for these processes to operate.
Conduction
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In conduction, heat travels from a warm object to a cold object until both reach equilibrium-i.e., both are the same temperature. For example, hands lose heat to wet line and metal gear.
Water conducts heat away from an object 25 times faster than air, which means that body heat will be drawn out of a person immersed in water at a rate 25 times faster than one just exposed in air. Water also has a tremendous heat capacity. It takes 1,000 times more heat to raise the temperature of a quantity of water one degree than it does to raise a similar quantity of air one degree. Therefore, water will continue to steal heat for far longer than will air and will drop your temperature to a much lower degree, because it needs so much more heat to raise its temperature. Remember, conduction doesn’t stop until both objects are the same temperature. Your body will not raise the temperature of the lake-the lake will bring your body down to its temperature.
Conduction and rescuers. The insulation a 1/4-inch (6 mm) neoprene ice rescue suit affords decreases water’s ability to conduct heat away from your body. However, don’t ignore heat loss from the feet. A thick pair of wool or fleece socks are recommended because an ice rescue suit’s boots are made of uninsulated rubber. Be prepared, and keep a pair of thick wool socks along with the extra gloves, hats, boots, and ice creepers in your car or rescue vehicle. Keep a pair of thick wool or fleece socks and glove liners in the bag of each exposure suit on the rescue vehicle. Avoid wearing cotton during winter calls. Cotton quickly absorbs water and allows it to evaporate your heat away.
(1) Severe injury can occur from the effects of cold well before clinical hypothermia is reached. Cold stress can decrease mental function, manual dexterity, and muscle strength, all of which rescuers need to be in peak condition when working on the ice. Always wear appropriate personal protective equipment. (Photos by authors.) (2) Wear hand protection that will give you the manual dexterity to work with carabiners, snap shackles, ice screws, pulleys, and other tools necessary for safe ice operations. Removing gloves or mittens to work with wet or metal objects is not an acceptable alternative. (3) If a victim has fallen through, the ice will not support standing divers and tenders. Tenders may need to tend from the water and therefore need to be protected as much as possible from immersion hypothermia. (4) Secure all tools and life support gear in the golden triangle chest area, and keep them in the same place on every dive. Should a cold-stressed diver need to access a pony regulator mouthpiece or pair of shears, it needs to be a reflexive maneuver or there is a good chance it won’t happen without increased mental stress and possible failure. (5) You must be very gentle in submersion/immersion patient handling and must have well-practiced, preplanned procedures. Remove victims horizontally from the water and keep them in that posture during transport.
Warm insulated gloves are imperative to prevent rope, metal equipment, wet bodies, and other heat-stealing objects from conducting heat away from your hands and thereby making them relatively useless. Good boots for Operations-Level personnel are important to keep the cold winter ground from robbing heat out of your feet. We lose 15 percent of our heat from our hands and 15 percent from our feet, so keep them insulated!
Conduction and patients. Conduction can still affect a patient even after you remove him from the water. Do not lay a patient directly on a cold backboard, which can conduct significant heat from the patient. Without a blanket, a backboard can conduct more heat away from the patient than the air above will. Transport devices stored in unheated compartments will be especially cold, as will devices constructed of metal. A stick-on backboard insulated pad can help solve this problem. Always remember: Insulation over, insulation under, and insulation all around. Secure a pad or noncotton blanket on the board as insulation under the patient.
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If a motor vehicle accident patient is placed on a cold, uninsulated backboard, the patient is likely to start or continue shivering, which increases the need for oxygen. If the patient’s ability to take in and transport oxygen is already decreased because of trauma, shock, near-drowning, or other conditions, then shivering might result in cardiac arrest. Think about it!
Also, a person who cannot move because of injury or because of immobilization will become colder much more quickly because the person cannot use voluntary muscle movement to generate heat. To make matters worse, the patient experiencing hemorrhagic shock is also more likely to become hypothermic. So, an immobilized trauma patient on an uninsulated backboard could be in serious risk of severe shock and even death because of heat loss that often can be prevented.
To make matters even worse, hypothermia increases bleeding time6, which means a hypothermic trauma patient is at a greater risk of hemorrhagic shock, which exacerbates the hypothermia. Rescuers must take as many measures as possible to prevent this vicious cycle.
Avoid using any sleds, boats, or transport devices that put patients or rescuers in contact with metal. Metal sleds, boats, and ladders rob the heat out from rescuers and patients. Also, as some childrens’ tongues have painfully discovered, wet skin can freeze to metal. Furthermore, metal transport devices are more likely to freeze to the ice itself, resulting in greater rescuer exertion and frustration.
Convection
Convection is the transfer of heat by wind or water movement. Your body is surrounded by a cushion of warm air or water heated through conduction. When wind or water movement carries away this warm air or water, your body loses heat as it warms the new surrounding medium. Every time the warm cushion is removed, the body must heat up the new surrounding medium.
Convection and rescuers. In winter water-related calls, SOPs/SOGs should include setting up a wind-protected staging area with vehicles, tarps, and other windbreaks. The few minutes it takes is worth it, and it can actually save time in the end. Remember, cold rescuers take longer to do the job safely and are at increased risk of causing injury. Wind speed and estimated operation duration should dictate the degree to which windblocks are set up.
Water does not have to be fast-moving for convection to occur; it can occur in still water. As soon as you move in water, convection takes place; the trickle of cold water entering a wetsuit quickly teaches that lesson. Also, smaller people in one-size-fits-all “dry” ice rescue suits are easily flooded and put at risk for significant heat loss.
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Moving water will take more heat out of you than will still water, so keep that in mind when deciding on effective PPE. Properly fitting immersion suits are important, especially in moving water. Standard neoprene ice rescue suits are not designed for moving water in any season and should definitely not be used in frigid moving water. These suits serve only as drysuits if the suit perfectly fits the rescuer’s body or if the rescuer is immersed only from the neck down. Unfortunately, most suits are designed for larger people; the surface ice rescue technicians should be of smaller build. We don’t want big, heavy people on the ice in surface ice rescue. Working in moving water also requires greater maneuverability and swimming ability, which these suits do not afford. True drysuits with winter-weight underwear are the preferred choice.
The human body loses at least 25 percent of its heat from the head, and heat escapes especially from the ears, nose, lips, scalp, carotid artery neck area, and face to the surrounding cold air. Fleece or wool balaclavas (hoods) are recommended for surface personnel because they cover the wearer’s ears, nose, neck, and mouth.
Convection and patients. In the case of accidental immersion, the victim should not kick around furiously while waiting for rescuers. Instead, conserve energy by bobbing and huddling. Swimming or working hard in cold water without proper personal protective equipment accelerates death. If you can float with as little movement as possible, then that is the first choice. If you are negatively buoyant and therefore cannot float, get training in bobbing techniques. If a person is buoyant enough, huddling can reduce heat loss.
A victim struggling in cold water will lose heat more quickly through convection than a still victim, even though the struggling victim may feel warmer. The latter is true because struggling increases metabolism and causes warm blood to be sent to the cold peripheral tissues, where the body has temperature sensors. So in the water, an increased feeling of warmth can coincide with greater heat loss. Rescuers exerting themselves in cold water need to keep this in mind.
Evaporation
In evaporation, a liquid changes to a vapor. This requires significant heat if the liquid is water because a large quantity of heat is required to raise the temperature of water. Sweating and perspiration use evaporation to keep the body cool in warm environments or when the body’s core temperature is higher than normal. The fluid continues to rob heat from the skin until the fluid is warm enough to change to a vapor and lift off the skin. Evaporation from the skin and respiratory tract is normally 20 percent of total heat loss. If the skin is wet from an external source, such as rain or immersion, that percentage increases.
Evaporation and rescuers. The colder the ambient air temperature, the more body heat required for skin to dry, which means it is important to dry yourself off if you exert yourself and perspire in the winter. For example, many of us have noticed that during a winter call we might actually feel warm when we exert ourselves, but once the rescue is over and the vehicles are cleaned and repacked, we suddenly feel wet and cold. Before you zip up that jacket, dry off your skin, especially around your torso and underarms.
It is very important to remove the wet exposure suits and wet gloves as soon as possible. Wet clothing or neoprene next to your skin acts like a big sweating machine, stealing your body heat to dry itself. As long as it is wet, the suit will steal your heat. If a suit must be worn more than once, make sure to don dry wool or fleece undergarments each time the suit is donned. Avoid cotton-cotton’s wicking effect causes increased evaporative heat loss.
Wet feet and hands lose heat more quickly than dry ones, making them more prone to cold injuries such as frostnip and frostbite. Waterproof foot protection is a must. Make sure your boots are high enough to prevent snow from entering.
Tenders should wear waterproof gloves or those made of pure wool or polar fleece so that they can handle wet lines, technicians, and equipment without great hand evaporative heat loss. Shredded newspaper can help if hands and feet become wet. Stuff shredded newspaper in gloves and boots for added insulation; replace it with a dry batch of newspaper when it becomes wet from perspiration or water.
A sports chamois is an excellent tool to keep with your jump kit all year round, because it is good for repeated use. At a prolonged call, you might need to dry yourself off several times to keep warm. One chamois does the job of many towels and can be thrown in the washer and dryer after use.
If your shirt becomes wet, if at all possible, change it. Teams performing strenuous, long-distance wilderness rescues should have extra shirts to change into after removing damp undergarments.
Rescuers cannot provide optimal patient care when they are cold.
Evaporation and patients. EMS personnel can probably picture a diabetic or cardiac patient soaking wet from perspiration in their ambulance. If the wet undergarments are not removed, that patient can remain cold all the way during a long transport drive, even in a very warm ambulance and even after being wrapped in blankets. Get the wet stuff off.
Patients pulled from the water are already hypothermic from conduction and convection in the water. After they are pulled from the water, they lose additional heat through evaporation.
Gently remove wet clothing and wrap patients as soon as possible in noncotton blankets, or put them in a thermal recovery stabilizer. Space blankets should be used only as wind protection on the outside of wool blankets. Space blankets work by reflecting heat. If the patient is hypothermic, there is little or no heat to reflect. Space blankets have no insulation or fluid-absorbing capabilities.
If local protocol allows, moisten and warm oxygen before administering it to cold patients. The last place you want to cause direct heat loss is in the core. Oxygen is normally stored in unheated ambulance compartments. Even if it is used from a warm jump kit, the decrease in pressure from 2,015 psi to ambient 14.7 psi can cause a drop in temperature in the oxygen regulator first stage to 22°F. Moisture is removed from the oxygen as it is compressed into cylinders. When we breathe, inhaled gas is moistened and brought up to body core temperature by the time it reaches the trachea. Then, every six to 10 seconds we exhale that warmed gas and replace it with new cold, dry gas that robs us of more heat and moisture. Therefore, breathing cold, dry gas causes heat loss by both evaporation and convection, directly from our core. Warming and moistening the oxygen prior to administration can be as simple as taping reusable heat packs to the outside of a $2 oxygen humidifier or in the field by running oxygen through a thermos of warm, distilled water heated with a few heat packs.
Radiation
Radiation is the emission of infrared energy. Proper PPE exposure equipment will help reduce heat loss from radiation. For rescuers and patients, make sure to protect well the significant heat loss areas such as the ears, nose, mouth, carotid neck region, and any place that has hair such as the underarms, the top of the head, and the groin.
PROTECTING PATIENTS
To emphasize the effects of heat loss on patients, picture a motor vehicle accident. The patient in the vehicle is not wearing a coat, hat, gloves, or boots. EMTs put a cold plastic collar (stored in the ambulance outside compartment) on the patient and adminster cold, dry oxygen directly to the patient’s core. As the fire department cuts the car apart, a new EMT stands outside excited and ready with the backboard and the Kendrick extrication device (KED), which ensures that these devices are as cold as can be before application. Next, EMTs cut away the patient’s clothing to expose injuries and apply the cold KED. Finally, the patient is laid on the very cold and even possibly wet backboard, if it has been snowing or raining. Inside the ambulance the medic administers IV fluid that was stored in a jump kit in a cold ambulance-cold fluid directly to the core. The patient crashes, and we wonder why. Now imagine that that patient was pulled out of an ice hole or a car partially submerged in freezing water.
What can we do differently? It is essential to do everything possible to keep the patient warm and avoid further heat loss. On the scene, do the following:
Keep equipment warm. Keep the backboard, KED, and other equipment that will come in contact with the patient in the warm ambulance until the very time it is needed. Wrap the oxygen tubing around a reusable heat pack a few times and then wrap that with a towel and tape it. Do not lay the cold, metal oxygen bottle anywhere against the patient. Get a warm oxygen humidifier ready in the ambulance, and make sure the IV fluids are warmed to at least ambient temperature.
Keep the patient warm. Insulate the backboard with a pad or blanket. Wrap the patient in blankets, from head to toe, getting as much as possible under the body and extremities without moving the patient. Put a hat and gloves on the patient if trauma isn’t a problem. If the patient is shivering, place wrapped, hand-size heat packs under the armpits.
Keep rescue/medical personnel warm. If not directly involved in the extrication operation, personnel can stay warm in the ambulance. Other medical personnel should wear warm gloves over their latex gloves while waiting, in addition to warm exposure wear.
Remove wet clothing. If the patient’s clothes are wet, remove them entirely once in the ambulance. Use a thermal recovery capsule, if available.
Handle the patient as carefully as possible. For immersion hypothermia patients, extra care, preplanning, and training are necessary to ensure patients are not dropped, yanked, and banged. Review the water-related incidents you have been part of or have watched. The average patient pulled from the water is dropped, yanked, and banged at least three times before being placed in the ambulance. This would be completely unacceptable in any other type of incident that does not have an immediate threat to rescuers. Once a patient is pulled from the water, there is no building about to collapse or fire about to engulf rescuers between the water and the ambulance. So why are uncontrolled rushing and lack of patient handling skills the norm for water incident scenes-particularly ice-related ones?
We believe the causes are cold, stressed rescuers; lack of ice and water training; poor understanding of cold stress and hypothermia; lack of SOPs/SOGs; lack of interagency preplanning and drilling with resulting weak or nonexistent incident command systems; and chaotic scenes.
RESCUE OPERATIONS
Cold water can quickly wear down even highly fit individuals. The U.S. Navy tells us, “In cold water, the ability to concentrate and work efficiency will decrease rapidly. Even in water of moderate temperature (60°F-70°F, 15.5°C-21.5°C) body heat loss to the water can quickly bring on diver exhaustion.”7
Avoid unnecessary exertion before, during, and after the rescue operation. Using an ice board for transporting equipment and personnel between shore and the victim greatly reduces exertion in surface and subsurface operations.
Plan ahead on how equipment and personnel will be transported from vehicles to the shore area. Rescue teams should look at all the potential sites in their district and have practiced plans on how to access them as easily and efficiently as possible. Consider the possibility of deep snow, for example, during this planning.
Technicians should perform facial immersion procedures immediately prior to performing water/ice operations, which is especially true for divers. We have observed that facial immersion for at least 15 seconds decreases the chances of a gasp reflex from occurring when a diver’s mask is dislodged underwater. Breath-holding facial immersions in cold water cause bradycardia (lowered heart rate). The degree of bradycardia is inversely proportional to water temperature.8 Preoperation facial immersion may increase the ability of rescuers to survive if something goes wrong.
Include pre- and postoperation blood pressure checks for technicians in surface and subsurface ice operations. Cold can increase blood pressure, immersion increases blood pressure, and cold water immersion can really increase blood pressure.
Cold causes peripheral vasoconstriction that pools blood in the core. More blood in a smaller place results in a higher pressure. Water exerts a little less than 0.5 psi per foot of pressure on the body, which also causes a pooling of blood in the body’s core. Cold and immersion diuresis (urine production) occurs when the blood pressure is raised from cold or immersion and the hypothalamus suppresses antidiuretic hormones, which allows the kidneys to filter more water from the blood, hence creating urine. Once water is filtered out of the blood and urine is created, the volume of blood is decreased, thereby decreasing blood pressure. The colder the water, the higher the rise in blood pressure, the more water is filtered from the blood, the more urine is created, the greater the decrease in blood volume. If you do not feel the need to urinate after 10 or so minutes of immersion in cold water, there is a good chance that you are dehydrated.
Check the technician’s blood pressure prior to the operation to make sure it is not too high. Check it after the technician has been suited down by a tender to make sure it is not too low. Low blood pressure is the concern here because after technicians are removed from the water and are placed in a warm vehicle or shelter, peripheral vasodilation occurs that shunts blood from the core to the peripheral tissues. The problem is that now there is a lower volume of blood to fill that larger space. A serious drop in blood pressure can occur if the technician was not properly hydrated. This is one of the reasons external rewarming techniques of hypothermic patients can cause “after-drop” or “rewarming” shock. This is simply a shock caused by a drop in blood pressure from the movement of a too-low blood volume back to a larger space, namely, the peripheral tissues in addition to the core. It is recommended that technicians drink eight or more ounces of water prior to performing an ice rescue. Warm, noncaffeinated, nonalcoholic fluids are even better.
Technicians and their chief tenders9 should remain together until the technicians have been checked out by EMS, rehydrated with warm fluids, and changed into dry clothing. If there are not enough personnel and the chief tender is needed elsewhere, the chief tender can turn the technician over to another qualified individual who will then assume those responsibilities.
SAFETY PRECAUTIONS
Keep in mind the following points at winter water rescue operations.
-Avoid unnecessary exposure to the cold, Wear appropriate PPE for the incident. If the victim has fallen through, ice will not support standing tenders and divers, and tenders may have to operate from the water. Hand protection should allow manual dexterity to work with carabiners, snap shackles, pulleys, and other tools necessary for safe ice operations. Removing gloves or mittens to work with wet or metal objects is not acceptable.
EMS personnel should wait in the warm ambulance until the victim is recovered and approaching the shore. Use radio communications to keep in contact with other rescuers, especially at long-distance operations.
-Avoid unnecessary exertion. Use an ice board to transport personnel and equipment to the rescue site. Transporting personnel and equipment across weak, breaking ice without an ice board increases the chances of failure. The ice board allows the diver to exit the water with a minimum of effort.
For divers, secure all tools and live support equipment in the golden triangle chest area, and keep them in the same place on every dive. Equipment can be more easily accessed by a well-practiced maneuver especially if the diver is cold-stressed.
-Handle victims carefully, and avoid further exposure to cold. Once the victim is removed from the water, rescuers should avoid rough handling. Procedures should be well-practiced and preplanned. Warm the equipment coming in contact with the victim, if possible, and keep the patient well insulated.
An understanding of cold stress and immersion hypothermia causes is crucial for keeping public safety personnel and victims as safe as possible. This understanding allows teams to develop standard operating procedures and guidelines to help prevent these problems and assists with making the risk/benefit analysis and on-scene plan of action. An understanding of hypothermia teaches us that contingency and self-rescue procedures must be reflexive because thought processes and mental and intellectual capacities may be well below normal. “Mental impairment is an early effect of general body cooling.”10 We cannot just assume “we will be okay.” Hypothermia can kill. Wear sufficient PPE, and never take shortcuts in training or with equipment and personnel. This is true for all cold-weather operations, be they a highway motor vehicle accident or a surface ice rescue.
Endnotes
- Mebane Y. “Hypothermia.” In Diving Medicine, Bove A. and J. Davis (eds.). W.B. Saunders, (1996), 96.
- Rennie, D.W. “Human thermal balance at rest and exercise in water: A review.” 9th Symposium on Under-water and Hyperbaric Physiology. UHMS, Bethesda MD, 1987, 95-107.
- Van Dorn, W., “Thermodynamic Model for Coldwater Survival.” Lang and Stewart (eds.). AAUS Polar Diving Workshop, San Diego, CA. 1991, 10-17.
- Hayward, J.S., J.Eckerson, and M.L. Collis. “Thermal balance and survival time prediction of man in cold water.” Canadian J. Physiol. Pharmacol. 53: 21-32.
- Keatinge, W.R. Survival in Cold Water: The Physiology and Treatment of Immersion Hypothermia and Drowning. Blackwell Scientific, Oxford.
- Valeri R., R. Dennis, A. Melaragno, and M. Altschule. “Resuscitation of hypothermic-hypovolemic hypotensive baboons.” In Human Performance in the Cold, Laursen R, R. Pozos, and F. Hempel (eds.). Undersea Medical Society, Inc.; 1982, 105-128.
- U.S. Navy Diving Manual Volume I (Air Diving) Revision 3, 1993. 0994-LP-001-9110, Best Publishing Company, 4-14.
- Schagatay E. and B. Holm. “Effects of water and ambient air temperatures on human diving bradycardia.” Eur J Appl Physiol; 1996: 73: 1-6.
- A technician may have five or six line tenders to help pull the technician and victim to shore, but each tender has only one chief tender. The chief tender’s sole responsibility is to the technician from the time of dressing right through rehab. The chief tender does not assist with the rescued patients.
- Abyholm, F.E. “The human organism in the cold.” Human Performance in the Cold.. Laursen G, R. Pozos and F. Hempel.. Undersea Medical Society. 1982, 85.
ANDREA ZAFERES teaches more than 1,500 police, fire, EMS, and sport divers annually throughout the United States, Canada, Asia, and the Caribbean in underwater vehicle extrication, PSD instructor training, field neurological evaluations, and homicidal drowning investigations. She is vice president of Lifeguard Systems and RIPTIDE, a NAUI and ACUC course director, a Red Cross and DAN instructor, a 14-year New York State EMT, and a member/trainer of the Ulster County Sheriff’s Office Dive Team. Zaferes is a Women’s Diving Hall of Fame inductee, an author, a public speaker, RIPTIDE magazine chief editor, manager of the www.wateroperation.com on-line discussion group, and an internationally known water rescue and recovery trainer.
WALT “BUTCH” HENDRICK has been training public safety dive/surface teams for more than 25 years in more than 15 countries. He is the founder and president of Lifeguard Systems and RIPTIDE. He began his dive and rescue career in the 1950s in his family’s watersport resort in Puerto Rico, where he started the San Juan offshore rescue team and ran the only civilian hyperbaric chamber in the Caribbean. Hendrick introduced in-water rescue breathing and the do-si-do position in 1967 and has since innovated many water operation procedures and equipment designs including the rescue throw rope bag. A published author, he teaches more than 1,500 students annually, is a public speaker, and has received many international awards. He co-authored with Zaferes Oxygen and the Scuba Diver, Field Neurological Evaluation, Scuba Instructor Readiness Series, Surface Ice Rescue, Public Safety Diving, and Ice Diving Operations.
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