Assessing feasibility and sex-related inequity in the Cardiac Rehabilitation Quality Indicators in Manitoba.

The Cardiac Rehabilitation Quality Indicators (CRQIs) developed by the Canadian Cardiovascular Society provide a means to standardize program assessment and identify sex-related inequities. No formal evaluation of the CRQIs has been conducted in Manitoba. An environmental scan for the CRQIs was performed using data in the electronic medical record at two cardiac rehabilitation (CR) sites in Winnipeg for 2016-2019 referrals. Of the 8116 referrals, 7758 (5491 males and 2267 females) had geographical access and were eligible for CR. The Manitoba Centre for Healthcare Data Quality Policy framework informed the data quality assessment. Thirteen CRQIs were available; four were considered high quality; nine demonstrated moderate to significant missing data. In addition to missing values, potential misclassification of risk (CR-4) and physiologically implausible and invalid dates were assessed and identified (CR-13 and CR-17). Each site had a physician medical director (CR-31) and a documented emergency response strategy (CR-32). Only high-quality data were evaluated for sex-related differences using Chi-square and median tests. Women had lower enrollment (CR-3), and more women enrolled after the median of 41 days (CR-2b). Engagement with CR partners, including frontline staff, and utilizing strategies to assess and limit physiologically implausible values and dates will enhance data capture and quality.

Contributions of Griffith Pugh to Success on Mt. Everest and His Impact on the Advancement of Altitude and Environmental Physiology.

Griffith Pugh, MD (1909-1994), was a pioneer in altitude physiology. During World War II, he developed training protocols in Lebanon to improve soldier performance at altitude and in the cold. In 1951 he was chosen to join the British Everest team as a scientist. In preparation, he developed strategies for success on a training expedition on Cho Oyu in 1952. Results from Cho Oyu led to the use of supplemental oxygen at higher flow rates during ascent than used previously (4 L/min vs 2 L/min) and continued use (at a reduced rate of 2 L/min) during descent, enabling increased performance and improved mental acuity. Oxygen was also used during sleep, leading to improved sleep and warmth. Adequate hydration (∼3 L/day) was also stressed, and a more appealing diet led to improved nutrition and condition of the climbers. Improved hygiene practices and acclimatization protocols were also developed. These strategies contributed to the first successful summiting of Mount Everest in 1953. Pugh was then appointed as the lead scientist for a ground-breaking eight-and-a-half-month research expedition where the team was the first to overwinter at high altitude (5800 m) in the Himalayas. This current work summarizes Pugh's scientific contributions as they relate to success on Mount Everest and in inspiring future altitude research by generations of successful researchers.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2024 Update.

The Wilderness Medical Society convened an expert panel to develop a set of evidence-based guidelines for the prevention and treatment of frostbite. We present a review of pertinent pathophysiology. We then discuss primary and secondary prevention measures and therapeutic management. Recommendations are made regarding each treatment and its role in management. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks or burdens for each modality according to methodology stipulated by the American College of Chest Physicians. This is an updated version of the guidelines published in 2019.

Wilderness Medical Society Clinical Practice Guidelines for the Treatment and Prevention of Drowning: 2024 Update.

The Wilderness Medical Society convened a panel to review available evidence supporting practices for acute management of drowning in out-of-hospital and emergency care settings. Literature about definitions and terminology, epidemiology, rescue, resuscitation, acute clinical management, disposition, and drowning prevention was reviewed. The panel graded available evidence supporting practices according to the American College of Chest Physicians criteria and then made recommendations based on that evidence. Recommendations were based on the panel's collective clinical experience and judgment when published evidence was lacking. This is the second update to the original practice guidelines published in 2016 and updated in 2019.

Heat Transfer Capabilities of Surface Cooling Systems for Inducing Therapeutic Hypothermia.

Therapeutic hypothermia (TH) is used to treat patients with cerebral ischemia. Body surface cooling provides a simple noninvasive method to induce TH. We compared three surface cooling systems (Arctic Sun with adhesive ArcticGel pads [AS]); Blanketrol III with two nonadhesive Maxi-Therm Lite blankets [BL]); and Blanketrol III with nonadhesive Kool Kit [KK]). We hypothesized that KK would remove more heat due to its tighter fit and increased surface area. Eight subjects (four females) were cooled with each system set to 4°C outflow temperature for 120 minutes. Heat loss, skin and esophageal temperature, and metabolic heat production were measured. Skin temperature was higher with KK (p = 0.002), heat loss was lower with KK in the first hour (p = 0.014) but not after 120 minutes. Heat production increased similarly with all systems. Core temperature decrease was greater for AS (0.57°C) than BL (0.14°C; p = 0.035), but not KK (0.24°C; p = 0.1). Each system had its own benefits and limitations. Heat transfer capability is dependent on the cooling pump unit and the design of the liquid-perfused covers. Both Arctic Sun and Blanketrol III cooling/pump units had 4°C output temperatures. However, the Blanketrol III unit had a greater flow rate and therefore more cooling power. The nonadhesive BL and KK covers were easier to apply and remove compared with the adhesive AS pads. AS had an early transient advantage in heat removal, but this effect decreased over the course of cooling, thus minimizing or eliminating any advantage during longer periods of cooling that occur during clinical TH. Clinical Trial Registration number: NCT04332224.

One Cool Guy: Scientific Contributions of John Hayward, Cold Water Pioneer.

John Hayward, PhD (1937-2012), was an early and significant contributor to the understanding of cold water immersion physiology and survival. This article summarizes his work on the 50th anniversary of his first publication in this area. He described areas of high heat loss and emphasized the importance of protecting these areas during cold exposure using the Heat Escape Lessening Posture (HELP) and the potential for heat donation to these areas during rewarming. He described several factors that affect the rate of core cooling, including body composition, behavior (swimming increases cooling whereas the HELP position decreases cooling), wet and wind, and thermal protective garments (dry suits offered much more protection than wet suits). Hayward determined breath-hold duration in children as young as 4 y and had his own heart catheterized for 3 d to complete 3 hypothermia rewarming trials. His work provided early understanding of the cold shock response and ways to mitigate its threat to survival. Hayward provided valuable contributions to prediction models for heat production, heat loss, and core cooling rates in cold water. He also developed a human model for severe hypothermia and patented the UVic Thermofloat Jacket. Finally, as evidence of his stature in the cold physiology community, Hayward was a coauthor of the initial State of Alaska guidelines for the treatment of hypothermia. John Hayward was truly a cold water pioneer.

Ground penetrating radar used to detect drowning victims under ice.

Every year, people drown after falling through ice on rivers and lakes. In some cases, the body of the victim floats up to the underside of the ice, making detection and recovery difficult using traditional search methods with divers. A robust and contact-less sensing system is required to locate drowning victims that does not put rescue teams at risk of falling through the ice themselves. In this paper, we demonstrate the feasibility of a ground penetrating radar (GPR) for detecting deceased drowning victims that have floated up to the underside of the ice. We placed three euthanized pigs simulating drowning victims under ice ranging in thickness from 5 to 26 cm. We dragged a GPR at 500 MHz and 1 GHz across the ice to detect the simulated victims using an autocorrelation-based detection technique. Results showed that both frequencies were able to detect the rough shape of the simulated victims at ice thicknesses up to 42 cm, with the 1-GHz data showing slightly more resolution than the 500-MHz data. These results show promise and suggest future development of an autonomous drone-based GPR detection system. Key points: Floating bodies are successfully detected under both ice and snow using a commercial ground penetrating radar system with ice depths reaching up to 26 cm in a controlled environment.The differences between using radar systems operating at/around 500 MHz and 1 GHz were not pronounced from the point of view of detection.Future studies should investigate the capabilities for detecting bodies in more realistic settings.

Survival After Being Wedged in a Crevasse for 16 Hours in Alaska.

We present a case of an un-roped mountaineer who fell into a crevasse during descent from the summit of Denali (Mount McKinley). He was wedged about 20 m deep in the crevasse for a total of 16 h; this included 4.5 h waiting for a rescue team to arrive, and an 11.5 h extrication process. His condition deteriorated and he eventually lost consciousness. Even though the rescue team collectively felt there was little or no chance of survival, they continued until the victim was extricated from the crevasse. He was almost immediately placed in a hypothermia wrap with active warming, loaded on a rescue helicopter, and transported for 1 h 40 min to a hospital in Fairbanks, Alaska. During the flight, he was placed on supplemental oxygen. He was cold to the touch; respiration was detectable, but a pulse was not, and he was responsive to verbal stimuli. Initial bladder temperature in hospital was 26.1°C. He was released from hospital after 14 d and made a full recovery. This case highlights an important mix of preventative and resuscitative lessons regarding crevasse rescue in an isolated location. The lessons include the dangers of travelling un-roped on a crevassed glacier, the challenges of extrication from a confined space, the fact that respirations are often more easily detected than pulses, an extended transport time to medical facilities, and the necessity of trying unorthodox extrication methods. This case emphasized the need to continue extrication and treatment efforts for a cold patient even when survival with hypothermia seems impossible.

Death After Crevasse Rescue in Antarctica.

We present a case report of a helicopter pilot who fell into a crevasse during a fuel delivery in Antarctica. He was trapped alone in the crevasse for 3 h while waiting for a rescue team to arrive, and a further 1 h during the extrication process. His condition deteriorated during the extrication and he lost consciousness and signs of life minutes after being dragged over the lip of the crevasse. He was then loaded into the rescue helicopter and treated with intermittent cardiopulmonary resuscitation during the 39-min return flight. Initial esophageal temperature on arrival at the Davis Base medical facility was 24.2°C. After 18 h of further treatment (mechanical ventilation with warm humidified O2, with internal and external warming) he was pronounced dead. The cause of death was hypothermia with minimal physical injury. This case highlights some of the extra challenges facing operational, rescue, and medical personnel in an isolated location. These complications include the tendency for flight crew to remove cold weather clothing during flight due to restricted mobility and excessive heat load from cabin heating; extended time for arrival of the rescue crew; extrication in a confined space; limited helicopter cabin space for transporting the rescue team and their rescue and medical equipment; and extended transport time to the nearest medical facility.

Spinal and corticospinal excitability in response to reductions in skin and core temperatures via whole-body cooling.

Cold stress impairs fine and gross motor movements. Although peripheral effects of muscle cooling on performance are well understood, less is known about central mechanisms. This study characterized corticospinal and spinal excitability during surface cooling, reducing skin (Tsk) and esophageal (Tes) temperatures. Ten subjects (3 females) wore a liquid-perfused suit and were cooled (9 °C perfusate, 90 min) and rewarmed (41 °C perfusate, 30 min). Transcranial magnetic stimulation (eliciting motor evoked potentials [MEPs]), as well as transmastoid (eliciting cervicomedullary evoked potentials [CMEPs]) and brachial plexus (eliciting maximal compound motor action potentials [Mmax]) electrical stimulation, were applied at baseline, every 20 min during cooling, and following rewarming. Sixty minutes of cooling reduced Tsk by 9.6 °C (P < 0.001), but Tes remained unchanged (P = 0.92). Tes then decreased by ∼0.6 °C in the next 30 min of cooling (P < 0.001). Eight subjects shivered. During rewarming, shivering was abolished, and Tsk returned to baseline, while Tes did not increase. During cooling and rewarming, Mmax, MEP, and MEP/Mmax remained unchanged from baseline. However, CMEP and CMEP/Mmax increased during cooling by ∼85% and 79% (P < 0.001), respectively, and remained elevated post-rewarming. The results suggest that spinal excitability is facilitated by reduced Tsk during cooling and reduced Tes during warming, while corticospinal excitability remains unchanged. ClinicalTrials.gov ID: NCT04253730. Novelty: This is the first study to characterize corticospinal and spinal excitability during whole-body cooling and rewarming in humans. Whole body cooling did not affect corticospinal excitability. Spinal excitability was facilitated during reductions in both skin and core temperatures.

Skin Cooling on Breath-Hold Duration and Predicted Emergency Air Supply Duration During Immersion.

PURPOSE: This study was intended to determine the effect of skin cooling on breath-hold duration and predicted emergency air supply duration during immersion.METHODS: While wearing a helicopter transport suit with a dive mask, 12 subjects (29 ± 10 yr, 78 ± 14 kg, 177 ± 7 cm, 2 women) were studied in 8 and 20°C water. Subjects performed a maximum breath-hold, then breathed for 90 s (through a mouthpiece connected to room air) in five skin-exposure conditions. The first trial was out of water for Control (suit zipped, hood on, mask off). Four submersion conditions included exposure of the: Partial Face (hood and mask on); Face (hood on, mask off); Head (hood and mask off); and Whole Body (suit unzipped, hood and mask off).RESULTS: Decreasing temperature and increasing skin exposure reduced breath-hold time (to as low as 10 ± 4 s), generally increased minute ventilation (up to 40 ± 15 L · min-1), and decreased predicted endurance time (PET) of a 55-L helicopter underwater emergency breathing apparatus. In 8°C water, PET decreased from 2 min 39 s (Partial Face) to 1 min 11 s (Whole Body).CONCLUSION: The most significant factor increasing breath-hold and predicted survival time was zipping up the suit. Face masks and suit hoods increased thermal comfort. Therefore, wearing the suits zipped with hoods on and, if possible, donning the dive mask prior to crashing, may increase survivability. The results have important applications for the education and preparation of helicopter occupants. Thermal protective suits and dive masks should be provided.Madu VC, Carnahan H, Brown R, Ennis K-A, Tymko KS, Hurrie DMG, McDonald GK, Cornish SM, Giesbrecht GG. Skin cooling on breath-hold duration and predicted emergency air supply duration during immersion. Aerosp Med Hum Perform. 2020; 91(7):578-585.

Comparison of Electric Resistive Heating Pads and Forced-Air Warming for Pre-hospital Warming of Non-shivering Hypothermic Subjects.

INTRODUCTION: Victims of severe hypothermia require external rewarming, as self-rewarming through shivering heat production is either minimal or absent. The US Military commonly uses forced-air warming in field hospitals, but these systems require significant power (600-800 W) and are not portable. This study compared the rewarming effectiveness of an electric resistive heating pad system (requiring 80 W) to forced-air rewarming on cold subjects in whom shivering was pharmacologically inhibited. MATERIALS AND METHODS: Shivering was inhibited by intravenous meperidine (1.5 mg/kg), administered during the last 10 min of cold-water immersion. Subjects then exited from the cold water, were dried and lay on a rescue bag for 120 min in one of the following conditions: spontaneous rewarming only (rescue bag closed); electric resistive heating pads (EHP) wrapped from the anterior to posterior torso (rescue bag closed); or, forced-air warming (FAW) over the anterior surface of the body (rescue bag left open and cotton blanket draped over warming blanket). Supplemental meperidine (to a maximum cumulative dose of 3.3 mg/kg) was administered as required during rewarming to suppress shivering. RESULTS: Six healthy subjects (3 m, 3 f) were cooled on three different occasions, each in 8°C water to an average nadir core temperature of 34.4 ± 0.6°C (including afterdrop). There were no significant differences between core rewarming rates (spontaneous; 0.6 ± 0.3, FAW; 0.7 ± 0.2, RHP; 0.6 ± 0.2°C/h) or post-cooling afterdrop (spontaneous; 1.9 ± 0.4, FAW; 1.9 ± 0.3, RHP; 1.6 ± 0.2°C) in any of the 3 conditions. There were also no significant differences between metabolic heat production (S; 74 ± 20, FAW; 66 ± 12, RHP; 63 ± 9 W). Total heat gain was greater with FAW (36 W gain) than EHP (13 W gain) and spontaneous (13 W loss) warming (p < 0.005). CONCLUSIONS: Total heat gain was greater in FAW than both EHP, and spontaneous rewarming conditions, however, there were no observed differences found in rewarming rates, post-cooling afterdrop or metabolic heat production. The electric heat pad system provided similar rewarming performance to a forced-air warming system commonly used in US military field hospitals for hypothermic patients. A battery-powered version of this system would not only relieve pressure on the field hospital power supply but could also potentially allow extending use to locations closer to the field of operations and during transport. Such a system could be studied in larger groups in prospective trials on colder patients.

Is active recovery during cold water immersion better than active or passive recovery in thermoneutral water for postrecovery high-intensity sprint interval performance?

High-intensity exercise is impaired by increased esophageal temperature (Tes) above 38 °C and/or decreased muscle temperature. We compared the effects of three 30-min recovery strategies following a first set of three 30-s Wingate tests (set 1), on a similar postrecovery set of Wingate tests (set 2). Recovery conditions were passive recovery in thermoneutral (34 °C) water (Passive-TN) and active recovery (underwater cycling; ∼33% maximum power) in thermoneutral (Active-TN) or cold (15 °C) water (Active-C). Tes rose for all conditions by the end of set 1 (∼1.0 °C). After recovery, Tes returned to baseline in both Active-C and Passive-TN but remained elevated in Active-TN (p < 0.05). At the end of set 2, Tes was lower in Active-C (37.2 °C) than both Passive-TN (38.1 °C) and Active-TN (38.8 °C) (p < 0.05). From set 1 to 2 mean power did not change with Passive-TN (+0.2%), increased with Active-TN (+2.4%; p < 0.05), and decreased with Active-C (-3.2%; p < 0.05). Heart rate was similar between conditions throughout, except at end-recovery; it was lower in Passive-TN (92 beats·min-1) than both exercise conditions (Active-TN, 126 beats·min-1; Active-C, 116 beats·min-1) (p < 0.05). Although Active-C significantly reduced Tes, the best postrecovery performance occurred with Active-TN. Novelty An initial set of 3 Wingates increased Tes to ∼38 °C. Thirty minutes of Active-C was well tolerated, and decreased Tes and blood lactate to baseline values, but decreased subsequent Wingate performance.

Wilderness Medical Society Clinical Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2019 Update.

To provide guidance to clinicians, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for the out-of-hospital evaluation and treatment of victims of accidental hypothermia. The guidelines present the main diagnostic and therapeutic modalities and provide recommendations for the management of hypothermic patients. The panel graded the recommendations based on the quality of supporting evidence and a balance between benefits and risks/burdens according to the criteria published by the American College of Chest Physicians. The guidelines also provide suggested general approaches to the evaluation and treatment of accidental hypothermia that incorporate specific recommendations. This is the 2019 update of the Wilderness Medical Society Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2014 Update.

Risk of Burns During Active External Rewarming for Accidental Hypothermia.

This article describes 3 incidents in which therapeutic or experimental warming of cold individuals caused first- to third-degree burns to the skin. Mechanisms for these injuries are considered. We conclude that active external rewarming of the trunk of a cold patient in the field can be administered safely and burn risk reduced if 1) manufacturer instructions are followed; 2) insulation is placed between the skin the and heat source; and 3) caregivers make regular efforts to observe heated skin for possible pending burn injury. Direct inspection is mandatory for the skin of areas that are on top of a heat source when the patient is lying on the heat source.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2019 Update.

The Wilderness Medical Society convened an expert panel to develop a set of evidence-based guidelines for prevention and treatment of frostbite. We present a review of pertinent pathophysiology. We then discuss primary and secondary prevention measures and therapeutic management. Recommendations are made regarding each treatment and its role in management. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks or burdens for each modality according to methodology stipulated by the American College of Chest Physicians. This is an updated version of the guidelines published in 2014.

Public knowledge, attitudes and practices of vehicle submersion incidents: a pilot study.

INTRODUCTION: Vehicle submersions account for up to 10% of all drownings in high-income countries. Reports indicate that occupants may be conscious and functional, but possibly making incorrect decisions for self-rescue leading to drowning. This study investigated current public knowledge, attitudes and practices regarding vehicle submersion incidents and to determine if individuals, who are aware of educational efforts regarding vehicle submersions, indicated better responses. METHOD: A knowledge, attitude and practice (KAP) survey was developed based on previous findings and guidelines from Operation ALIVE (Automobile submersion: Lessons In Vehicle Escape) for vehicle submersion incidents. RESULTS: The majority of respondents (87%) had knowledge of vehicle submersions from the media, but they were not aware (94%) of an effective self-rescue protocol. Respondents felt they had low risk of involvement in a vehicle submersion, and that the chance of survival was likely. Most respondents selected a "successful" initial action for escape; however, other responses indicate the chances of completing a successful self-rescue sequence was less likely. Only 45% of respondents were "aware" of Operation ALIVE educational initiatives, and this awareness did not generally produce better responses. CONCLUSIONS: Public understanding of vehicle submersion incidents is low and current public education efforts have not increased awareness in the severity or the urgency for performing self-rescue in this scenario. Simply increasing public knowledge of "SWOC" ("SEATBELTS" off, "WINDOWS" open, "OUT" immediately, "CHILDREN" first) would help to decrease the high fatality rate associated with this type of road traffic accident.

Human Responses to 5 Heated Hypothermia Wrap Systems in a Cold Environment.

INTRODUCTION: We compared the effectiveness of 5 heated hypothermia wrap systems. METHODS: Physiologic and subjective responses were determined in 5 normothermic subjects (1 female) for 5 heated hypothermia wraps (with vapor barrier and chemical heat sources) during 60 min of exposure to a temperature of -22°C. The 5 systems were 1) user-assembled; 2) Doctor Down Rescue Wrap; 3) hypothermia prevention and management kit (HPMK); 4) MARSARS Hypothermia Stabilizer Bag; and 5) Wiggy's Victims Casualty Hypothermia Bag. Core and skin temperature, metabolic heat production, skin heat loss, and body net heat gain were determined. Subjective responses were also evaluated for whole body cold discomfort, overall shivering rating, overall temperature rating, and preferential ranking. RESULTS: The Doctor Down and user-assembled systems were generally more effective, with higher skin temperatures and lower metabolic heat production; they allowed less heat loss, resulting in higher net heat gain (P<0.05). HPMK had the lowest skin temperature and highest shivering heat production and scored worse than the other 4 systems for the "whole body cold discomfort" and "overall temperature" ratings (P<0.05). CONCLUSIONS: The user-assembled and Doctor Down systems were most effective, and subjects were coldest with the HPMK system. However, it is likely that any of the tested systems would be viable options for wilderness responders, and the choice would depend on considerations of cost; volume, as it relates to available space; and weight, as it relates to ability to carry or transport the system to the patient.