An interventional study of Forced air warming in Hypothermia Due to Cold Environment, sponsored by Haukeland University Hospital. Enrolling by invitation at 1 site in Norway. Open to participants aged 18 Years to 45 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-03-04.
Sponsored by Haukeland University Hospital · Not applicable, Interventional, and Other
Forced air warming may be a feasible strategy for prehospital rewarming of patients with accidental hypothermia. This pilot study will explore the feasibility of this technique which has not been studied outside of hospital.
Accidental hypothermia is defined as an involuntary drop in core body temperature below 35°C.
Hypothermia is a risk factor for cardiac arrythmia, pulmonary oedema, coagulopathy and neurological pathology. Isolated accidental hypothermia is potentially lethal on its own, and it is also an independent risk factor for increased mortality in patients with traumatic injury.
When core temperature drops, the body will automatically activate compensatory mechanisms in order to both increase thermic production and minimize heat loss in order to restore normal temperature. The mechanisms for thermal homeostasis are complex, strictly regulated and effective.
Until quite recently, active external rewarming was considered to be harmful and dangerous for patients with accidental hypothermia. A fear of fatal complications such as increased afterdrop and "rearming syndrome" leading to dangerous arrythmias and a drop in blood pressure which in a worstcase scenario could lead to circulatory collapse, shock and potentially death.
Given the potentially detrimental consequences of being cold, any advice to abstain from warming patients should be well-documented, and the adverse effects of warming should outweigh those of being hypothermic. The lack of evidence for this claim that active external rewarming is dangerous along with many reports of successful external rewarming is leading to a change in most guidelines where active external rewarming is now an advisable treatment option. A variety of different technological devices exist for the purpose of rewarming, but there is no established standard which is proven superior to others. Several trials have compared different rewarming methods, but evidence is limited. There is particularly deficient evidence regarding the amount of heat available for transfer from different methods and also the required amount of heat transfer for the rewarming to have a significant clinical impact. There is however reason to be cautious with active external rewarming of hypothermic patients. In a normothermic patient with normal circulatory function, thermal energy will be absorbed by the blood which flows back into central circulation distributing the heat evenly into a large volume. In a hypothermic patient there will be less cutaneous blood flow and less heat will be transferred to systemic circulation. This means that heat will accumulate on the skin surface and increase the risk of cutaneous injury, and there are several reported cases of this. Hypothermia research with volunteer research participants is a complicated matter for many reasons.
One complicating factor is shivering, which is an autonomic defense mechanism in which the muscles contract rapidly producing heat. It is the most effective method for the body to increase the metabolic heat production and re-establish normothermia. The shivering response is complicated in a research setting because there is a large interindividual variation in temperature threshold for initiation of shivering and in shivering intensity. This means that if research participants are cooled down they will start to shiver at different core temperatures and with different intensities.
Standardization of data is therefore impossible, and the researcher will be measuring the interindividual shivering abilities of the different research participants instead of the effect of the intervention. Shivering must therefore be inhibited in order to achieve reliable data.
Inhibition of shivering for research has been done several times before. The most common method to achieve this is through intravenous administration of a drug called Meperidine which is a synthetic opioid with good shivering inhibition attributes. A protocol for inhibition of shivering in patients with simulated accidental hypothermia has been developed by Helland et. al., which we intend to use in this experiment. Given the results of our previous studies (REK 714469 and REK 855256, results not yet published) where we have documented limited effects of traditional treatment options in non-shivering participants, we believe that alternative strategies must be investigated. Forced Air Warming (FAW) is a commonly used method for rewarming from hypothermia in an in-hospital setting, but it has limited evidence for prehospital use. FAW enables heat transfer to a much larger surface area compared to, for example, an electric heating blanket, which may contribute to significantly higher rewarming rates.
449 studies on the registry are indexed under Hypothermia; 54 are open to participants now.
This study's planned enrollment of 4 is below the median of 77 across 328 interventional studies indexed under Hypothermia.
Browse Hypothermia studies →Haukeland University Hospital is the lead sponsor of 284 studies on the registry; 59 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Excipients
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Platelets
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
QT and QTc
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
All participants.
Device: Forced air warming
Prehospital use of forced air warming
Esophageal temperature
Changes in body temperature of participants measured in the esophagus
Time frame: 1 hour
Feasibility of the experimental procedure
Practical problems involving the experimental design.
Time frame: 3 hours
Air temperature
We will measure the temperature of the air warming the patient.
Time frame: 1 hour
Air velocity
We will measure the air velocity entering the wrap where the patient is placed.
Time frame: 1 hour
Air particle concentration
We will measure the amounts of oxygen (o2) and carbon dioxide (CO2) in the warmed air.
Time frame: 1 hour
Subjective comfort
We will regularly ask the participants how they are feeling using a validated subjective scoring form.
Time frame: 3 hours
Ambient air temperature
We will measure the temperature in the cold chamber continously
Time frame: 3 hours
Plan to share: No — GDPR
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