Immersion Suit Research Articles

Thermal response of human body with immersion suit in cold environment.

Hypothermia caused by cold water immersion is one of the main causes of death in marine accidents. Immersion suit is a kind of protective clothing when implementing flying tasks over the sea in cold seasons, with the main function to slow down the loss of human heat in water and prolong the survival time. In this study, the thermal properties and wearing types of immersion suit and underwear were analyzed. The subjects with internal- and external-wear immersion suit exposed to the experimental environments for 2h in five working conditions. The core temperature, weighted average skin temperature, and average body temperature were measured and calculated. Both internal- and external-wear immersion suits could fulfil the cold protection requirements under the experimental conditions. The results of clothing parameter tests and physiological experiments both exhibit that the external-wear immersion suit has better thermal insulation effect. And the tolerance time in low-temperature water was predicted, which is crucial for effective and efficient rescue during shipwreck in adverse thermal scenarios. In future research, a comprehensive evaluation and analysis of the thermal insulation performance of immersion suit could be completed in combination with the water ingress of the clothing, the subjects' thermal comfort, and flexibility of the clothing.

An experimental analysis of the impact of thermal protective immersion suit and angle of heel on individual walking speeds

The cold environment of Polar Regions introduces additional challenges to maritime safety in situations where it becomes necessary to abandon a vessel. The Polar Code requires all vessels operating in Polar Regions to be equipped with approved thermal protective clothing suitable for immersion in polar waters (thermal protective immersion suit (TPIS)) for all passengers and crew. However, in addition to assessing thermal protection offered by TPIS, given the criticality of time in emergencies, it is essential to understand their impact on walking performance during evacuation and how this may be impacted by adverse vessel orientation. The ARCEVAC (ARCtic EVACuation) project examines the impact of two different types of TPIS (Suit-1 and Suit-2) on walking speed at 0°, 10°, 15° and 20° angles of heel. A test facility representing a 36 m long ship’s corridor was developed and 210 volunteers recruited to participate in the trials. Project findings reveal that male performed considerably better than female counterparts and increases in age, weight and heel angle had significant adverse impact on walking speed while increase in height resulted in significant increase in walking speed. Furthermore, the specific nature of the TPIS had an impact on walking speed, with the most severe reduction in walking speeds being 38% for Suit-2 and 29% for Suit-1 at 20° of heel. Reductions in walking speed of this magnitude can have a profound impact on evacuation and so cannot be ignored from evacuation analysis.

Modified immersion suits for helicopter aircrew: Evidence for improved conspicuity from sea trials

In this article we evaluate a modified immersion suit for use by helicopter aircrew. Helicopter aircrew operating over water are subject to international regulations which govern the personal protective equipment and clothing worn. Our modification increases the area of retroreflective material in a unique configuration. Highly reflective materials can cause unwanted reflections in the cockpit and data as to their efficacy in improving conspicuity in rescue at sea has not previously been captured. In this study we address this problem. Two methods were developed to test the acceptability and efficacy of a modified immersion suit to improve conspicuity in rescue operations at sea. Firstly, land-based trials employing subject matter experts were conducted to assess the tolerability of reflections in the cockpit from the modifications made to the immersion suit. Secondly, trials at sea using UK search and rescue teams captured data to assess the efficacy of the modification. Our results provide preliminary evidence for the acceptability of the modified immersion suit design and that the modification improves conspicuity in night time conditions, measured using the distance at which a target is detected. Our results support re-examination of the standard associated with passive lifesaving systems in helicopter aircrew immersion suit design to include an increase in the area of retroreflective material in the proposed novel configuration. Finally, our results support the use of coloured retroreflective tape to provide increased visual contrast, especially where this colour is coordinated with the main suit fabric.

The influence of cockpit solar loading on offshore pilot cognitive performance

The goal of this research was to develop greater understanding of how environmental factors such as passive heat stress (through cockpit solar loading) might influence performance of offshore helicopter pilots who are completing simulated in-flight emergencies. Real-time physiological data such as heart rate, respiration, skin temperature, and eye tracking were used as objective quantitative measures to contextualise performance based on realistic environmental conditions. Results indicated a significant difference in skin temperature (Tskin) when comparing baseline (denoted as normal training conditions in this study) and testing completed after being exposed to passive heating for 90 minutes in 30°C ambient air temperature. Results also indicate that there were significantly higher numbers of fixations and increased index of cognitive activity (ICA) after passive heating. It is recommended that pilots are provided the opportunity to complete flight simulator training/assessment while wearing full flight ensemble (e.g., immersion suit, gloves, life vest, helmet/headset, etc…).

Forgetting of marine emergency duties tasks: Predictors of relearning

In emergencies at sea, it is crucial that the crew members remember emergency tasks. Although these practical skills are occasionally trained for, some are not routinely practiced and it is expected that performance of these skills will degrade over time. This program evaluation addresses whether characteristics can predict performance of marine emergency skills. Specifically, during relearning of two equipment preparation and donning tasks included in marine emergency duties refresher (MED-R) courses. The time since an individual had completed prerequisite training, the type of course (for Officers or Ratings), and the age of the individual were hypothesized to be significant predictors of performance patterns in this initial cohort of trainees. While very few trainees produced errors during an immersion suit task, more than half of trainees produced errors during a breathing apparatus task. The relationships between the predictors and breathing apparatus task error scores were statistically reliable, and 7% of the variance in performance is accounted for. Future research questions should focus on understanding additional factors that may aid in predicting relearning performance. Comparison of the two tasks examined, which differed in complexity, provides support for the role of task difficulty in theoretical understanding of differences in relearning of movement skills. In terms of practice, we can conclude that the individual factor of age and the training factors of timing and level can aid in predicting relearning performance. Further study of additional individual and training factors can bolster our ability to predict relearning outcomes, leading to effective and efficient training decisions.

The development and validation of key performance indicators for two tasks related to Marine Emergency Duties training

ABSTRACTUsing Delphi methodology, we created measurement instruments for specific training tasks included in Marine Emergency Duties training. Six Marine and Offshore Safety and Survival instructors rated items important for immersion suit and self-contained breathing apparatus (SCBA) donning tasks. Consensus was reached, and an item was included on the final checklist when at least 80% of the experts rated the importance of the item as greater than or equal to four out of five. After one round of surveys, panelists reduced items from 12 to five for the immersion suit donning task and from 30 to 19 for the SCBA donning task. Delphi methodology allowed for the creation of checklists that can be used to assess trainee competence for two specific tasks. These checklists will aid researchers and educators in measuring performance within a course environment while producing as little interference with the instructional experience as possible.

Factors associated with crewmember survival of cold water immersion due to commercial fishing vessel sinkings in Alaska

Occupational fatality surveillance has identified that fishing vessel disasters, such as sinkings and capsizings, continue to contribute to the most deaths among crewmembers in the US fishing industry. When a fishing vessel sinks at sea, crewmembers are at risk of immersion in water and subsequent drowning. This study examined survival factors for crewmembers following cold water immersion after the sinking of decked commercial fishing vessels in Alaskan waters during 2000–2014. Two immersion scenarios were considered separately: immersion for any length of time, and long-term immersion defined as immersion lasting over 30min. Logistic regression was used to predict the odds of crewmember survival. Of the 617 crewmembers onboard 187 fishing vessels that sank in Alaska during 2000–2014, 557 (90.3%) survived and 60 died. For crewmembers immersed for any length of time, the significant adjusted predictors of survival were: entering a life-raft, sinking within three miles of shore, the sinking not being weather-related, and working as a deckhand. For crewmembers immersed for over 30min, the significant adjusted predictors of survival were: wearing an immersion suit, entering a life-raft, working asa deckhand, and the sinking not being weather-related. The results of this analysis demonstrate that in situations where cold water immersion becomes inevitable, having access to well-maintained, serviceable lifesaving equipment and the knowledge and skills to use it properly are critical.

Correction factors for assessing immersion suits under harsh conditions

Many immersion suit standards require testing of thermal protective properties in calm, circulating water while these suits are typically used in harsher environments where they often underperform. Yet it can be expensive and logistically challenging to test immersion suits in realistic conditions. The goal of this work was to develop a set of correction factors that would allow suits to be tested in calm water yet ensure they will offer sufficient protection in harsher conditions. Two immersion studies, one dry and the other with 500 mL of water within the suit, were conducted in wind and waves to measure the change in suit insulation. In both studies, wind and waves resulted in a significantly lower immersed insulation value compared to calm water. The minimum required thermal insulation for maintaining heat balance can be calculated for a given mean skin temperature, metabolic heat production, and water temperature. Combining the physiological limits of sustainable cold water immersion and actual suit insulation, correction factors can be deduced for harsh conditions compared to calm. The minimum in-situ suit insulation to maintain thermal balance is 1.553–0.0624·TW + 0.00018·TW2 for a dry calm condition. Multiplicative correction factors to the above equation are 1.37, 1.25, and 1.72 for wind + waves, 500 mL suit wetness, and both combined, respectively. Calm water certification tests of suit insulation should meet or exceed the minimum in-situ requirements to maintain thermal balance, and correction factors should be applied for a more realistic determination of minimum insulation for harsh conditions.

Comparison of thermal manikins to human thermoregulatory responses

Immersion suits are lifesaving appliances (LSA) designed to protect the wearer if they become accidently immersed in cold water by reducing the cold shock response and delaying the onset of hypothermia. Immersion suits are certified to both national and international standards; some of which require the thermal protective properties to be tested using humans or thermal manikins. The ethical nature of testing with humans has been questioned [1] due to the physically grueling nature of these tests, thus testing with manikins may be preferential. However, previous work has shown that discrepancies exist between thermal manikins and humans that could result in immersion suit selection that would benefit the former more than the latter who would ultimately use it [2]. This study investigated the thermoregulatory responses of humans and compared them to a thermal manikin while wearing immersion ensembles with insulation distributed in various configurations hypothesized to be beneficial to humans and manikins.

Protecting aircrew from cold stress elevates heat stress

Aircrew need to wear an immersion suit to protect against hypothermia in the unlikely event of crashing into cold water. These clothing configurations provide insulation and water tight seals to reduce body heat loss in water; however, heat loss will also be impaired during normal flying activities in a warm cockpit. Therefore, this study evaluated the heat exchange properties of the Aircrew Protective Clothing Configuration (APCC) to determine the limitations it may impose to work in warm environments.

Reduction in predicted survival times in cold water due to wind and waves

Recent marine accidents have called into question the level of protection provided by immersion suits in real (harsh) life situations. Two immersion suit studies, one dry and the other with 500 mL of water underneath the suit, were conducted in cold water with 10–12 males in each to test body heat loss under three environmental conditions: calm, as mandated for immersion suit certification, and two combinations of wind plus waves to simulate conditions typically found offshore. In both studies mean skin heat loss was higher in wind and waves vs. calm; deep body temperature and oxygen consumption were not different. Mean survival time predictions exceeded 36 h for all conditions in the first study but were markedly less in the second in both calm and wind and waves. Immersion suit protection and consequential predicted survival times under realistic environmental conditions and with leakage are reduced relative to calm conditions.

Immersion Suit Donning in Dynamic Environments: Implications for Design, Construction & Use

Marine abandonment immersion suits are a vital piece of safety equipment intended to protect individuals from exposure to harsh environmental elements. The operational effectiveness of a well maintained and fitted suit depends on the ability of a user to correctly don a suit system. Thirty‐two participants performed immersion suit donning trials in six experimental conditions. Dynamic, pre‐abandonment marine emergency scenarios were simulated using a six degrees of freedom motion platform and varying environmental lighting levels. This article details user‐suit interaction challenges encountered throughout immersion suit donning tasks and examines their connection to safety and survival in marine emergencies. Analysis of user‐suit functionality during the donning process is critical for identifying current deficiencies in order to develop future design solutions, training methodologies and ultimately improve users’ practical competencies.

Initial Heat Stress on Subsequent Responses to Cold Water Immersion While Wearing Protective Clothing

In cold water emergency situations, helicopter aircrew will enter the water with a raised body temperature due to wearing immersion suits. Prewarming has been demonstrated to accelerate core cooling during subsequent cold water immersion (CWI) when wearing swimsuits. For this study we hypothesized that wearing an immersion suit would slow the rate of cooling in subjects who were prewarmed compared to those kept in a normothermic state. Two different groups of male subjects (age, 24.7 +/- 4.2 yr; height, 183.1 +/- 6.5 cm; weight, 86.7 +/- 15.0 kg; body fat, 16.8 +/- 3.3%) were used to gather data under two conditions: prewarming by exercise (Warm-CWI) and baseline (Base-CWI) when wearing a dry immersion suit (2.97 Clo). In Warm-CWI, seven subjects rested for 20 min and then cycled on an ergometer cycle for 20 min before immersion in water at 5 degrees C for 140 min. In Base-CWI, six subjects were directly immersed in 5 degrees C water after resting. Tre and Tsk were significantly higher after Warm-CWI at start of CWI, resulting in faster core cooling rate, and a drop in Tre and Tsk during the first 10 min. In the long term, the overall core cooling did not differ between Warm-CWI (0.34 +/- 0.11 degrees C x h(-1)) and Base-CWI (0.31 +/- 0.05 degrees C x h(-1)). Wearing a dry immersion suit eliminates long-term differences in core cooling between prewarmed subjects and those kept in a normothermic state. When entering cold water with a raised Tre and Tsk, different thermal responses during the first 10 min are expected, but this does not alter long-term core cooling.

Leg Exercise and Core Cooling in an Insulated Immersion Suit Under Severe Environmental Conditions

This study was conducted to examine whether the greater rate of heat production through intermittent leg exercise would offset an elevated rate of heat loss and thereby decrease the rate of core cooling during immersion in severe conditions when wearing an insulated immersion suit. On two separate days, seven male subjects were immersed in 2 degrees C water with air temperature of -2 degreesC, wind speed of 5 m x s(-1), and waves of 30-40 cm high. Subjects wore wool underwear, flight suits, and neoprene immersion suits. They were immersed for 180 min while remaining passive (NonEx) or performing moderate leg exercise for 5 min every 20 min (LegEx). Metabolism, rectal and skin temperatures, and skin heat flux were measured. Subjective evaluation of thermal and physical comfort was obtained. After 180 min core cooling was less in LegEx (0.3 degrees C) compared to NonEx (0.9 degrees C). This was attributed to a 31% increase in total heat production, but there was only a 21% increase in total heat loss when performing leg exercise compared to lying still. Leg exercise also improved thermal and physical comfort. The results suggest that wearing an insulated immersion suit under extreme environmental conditions and 5 min of leg exercise every 20 min might improve heat balance, resulting in a net heat gain (10%) compared to lying still in the water. As a result, shivering intensity is reduced, core cooling rate, and thermal and physical comfort is improved. This procedure potentially provides a practically significant survival advantage at sea and also under severe conditions.

ECG During Helicopter Underwater Escape Training

Coincidental stimulation of the sympathetic and parasympathetic nervous system can cause "autonomic conflict" and consequent cardiac arrhythmias. The present study tested the hypotheses that: 1) cardiac arrhythmias would be seen in those undertaking helicopter underwater escape training (HUET); 2) the occurrence of arrhythmias in individuals could be predicted; and 3) the heart rate response to HUET would habituate with repeated runs. There were 26 male volunteers who each undertook 5 HUET submersions into water at 29.5 degrees C, with each run separated by 10 min. Each submersion included a 3-min, 40-s pre-submersion period, a 10-s submersion, and 40-s post-submersion period. Participants wore a three-lead telemetric ECG system beneath an immersion suit and underclothing. Skin temperature was measured in one participant. Each participant undertook tests to establish their autonomic function, including heart rate variability, face immersion, cold pressor test, and aerobic capacity assessment. The heart rate response to HUET was reduced by the fourth run when compared to the first run. Across all runs, 32 cardiac arrhythmias were identified (25%) in 22 different participants; all but 6 of the arrhythmias occurred just after submersion. Only aerobic fitness appeared inversely associated with the occurrence of arrhythmias. The heart rate response to HUET habituates. HUET produces cardiac arrhythmias; these are asymptomatic and probably of little clinical significance in young, fit individuals. It remains to be seen if this is the case with either an older, less fit cohort of people or in those undertaking longer breath holds in colder water.

Effects of human anthropometry and personal protective equipment on space requirements

Representative samples of offshore workers engaged in the use of totally enclosed lifeboats were recruited in two different regions of Atlantic Canada for this study. Body mass, height and three selected anthropometric dimensions were measured with and without the presence of an immersion suit. Statistical comparisons were made between the two groups and to the main criteria values for body weight and space allocation used international standards for lifeboat capacity rating. There was no difference in the height, body mass and BMI values between the two groups. Both groups were found to be considerably heavier than the IMO Life Saving Code standard of 75 kg. Not surprisingly, the shoulder breadths measurements were always greater than the hip breadth measurements. The seat pan allocation of 430 mm was found to be inadequate for this population and needs to be increased. Finally, the wearing of an immersion suit increases the physical size of each subject by substantial amounts. The magnitude of increase is related to the type of suit and whether there was external compression applied during the measurement. It was recommended that the international standard should be altered by reducing the lifeboat capacity ratings by 20%.

Acute Lower Limb Ischemia Associated with Use of an Immersion Suit

External compression is a rare cause of acute lower limb ischemia. Workers required to wear immersion suits during helicopter simulation training are exposed to external compressive forces which can alter the hemodynamics in arterial bypass conduits. Herein a case of arterial thromboembolization to the lower limb following the wearing of an immersion suit, in a patient who had undergone arterial bypass surgery 13 yr previously is presented. The potential for this episode of acute leg ischemia being a direct result of the compressive forces exerted by the immersion suit and the possible implications for wearers of immersion suits following arterial graft surgery is discussed.

Heat Stress of Helicopter Aircrew Wearing Immersion Suit

The objectives of the present study were to define the lowest ambient air and cabin temperatures at which aircrews wearing immersion protection are starting to experience thermal discomfort and heat stress during flight operations, and to characterize during a flight simulation in laboratory, the severity of the heat stress during exposure to a typical northern summer ambient condition (25 degrees C, 40% RH). Twenty male helicopter aircrews wearing immersion suits (insulation of 2.2 Clo in air) performed 26 flights within an 8-month period at ambient temperatures ranging between -15 and 25 degrees C, and cabin temperatures ranging between 3 and 28 degrees C. It was observed based on thermal comfort ratings that the aircrews were starting to experience thermal discomfort and heat stress at ambient and cabin air conditions above 18 degrees C and at a WBGT index of 16 degrees C. In a subsequent study, seven aircrews dressed with the same clothing were exposed for 140 min to 25 degrees C and 40% RH in a climatic chamber. During the exposure, the aircrews simulated pilot flight maneuvers for 80 min followed with backender/flight engineer activities for 60 min. By the end of the 140 min exposure, the skin temperature, rectal temperature and heart rate had increased significantly to 35.7 +/- 0.2 degrees C, 38.4 +/- 0.2 degrees C and between 110 and 160 beats/min depending on the level of physical activity. The body sweat rate averaged 0.58 kg/h and the relative humidity inside the clothing was at saturation by the end of the exposure. It was concluded that aircrews wearing immersion suits during the summer months in northern climates might experience thermal discomfort and heat stress at ambient or cabin air temperature as low as 18 degrees C.

Personal protective equipment affecting functional anthropometric measurement

This study provides information on the affects of immersion suit wear on the maximum reach envelope of industrial offshore workers. In this study the total maximum reach envelope was measured using a computerized potentiometric system which records the 3-dimensional reach volume. The reach volume was then partitioned into vertical and horizontal sectors to closely examine the effect of the suit on the reach. Specific regions of the maximum reach envelope were significantly affected by the use of the suit. The changes were documented in terms of the linear changes in vertical reach and angular changes in shoulder motion.

Submarine Escape Trials 1999-2001 -Provision of Medical Support

Since the early 1960s all Royal Navy submarines have been fitted with an escape system comprising a single escape tower (SET) and submarine escape immersion suit (SEIS). This system enables escape from a submarine at a depth of 180 metres (1.9 MPa) provided that the submarine compartment is at a pressure of no greater than 1 bar (0.1 MPa). Due to a variety of causes which may include flooding and leakage of high pressure air systems it is the highly probable that the submarine compartment will be at a pressure in excess of 1 bar (0.1 MPa) at the time of the escape. To investigate and determine what constitutes a 'safe' maximum escape depth from any given compartment pressure (the safe to escape curve), a purpose built chamber complex, the Submarine Escape Simulator (SES) has been constructed at the QinetiQ, formerly the Defence Evaluation and Research Agency (DERA), Alverstoke site. Unlike escapes from a submarine where once released from the submarine the escapee's ascent can not be halted, within the SES it is possible to halt the ascent phase. This article describes the systems and procedures developed to enable medical support to be provided rapidly to a subject at any stage of the compression decompression profile. The article also provides details of the results to date that have been obtained from this work.