Effectiveness of Heat Donation Through the Head or Torso on Mild Hypothermic Rewarming

The study will compare the rewarming effectiveness of heat donation through the head or the torso during rewarming of mildly hypothermic subjects. Warming will be accomplished through either forced-air warming or using a charcoal heater; both units are commonly used for warming. The investigators hypothesize that head warming will be as, or more, effective compared to

Study Overview

• Status: Completed
• Conditions: Rewarming by Shivering Heat Production Only; Rewarming by External Heat to the Torso; Rewarming by External Heat to the Head
• Intervention / Treatment: Device: Rewarming modality

Detailed Description

Dr. Gordon Giesbrecht is studying/comparing the effectiveness of heat donation through the head or the torso in rewarming a mildly hypothermic individual. A rigid forced-air warming cover for the head or the torso will be used to rewarm the hypothermic individuals.

Subjects will be asked to participate in three experimental trials, separated by at least 48 hours. Each trial will last about 4 hours (1 hour for setup, 1 hour for cooling, and 2 hours for rewarming and removal of instrumentation).

On each of the three trials, subjects will undergo immersion to the level of the sternal notch in a tank of 8˚C water for up to 60 minutes. They will then exit the water, be dried off and lie in a hooded sleeping bag with the head inside the hood where one of the three warming procedures will be administered for 60 minutes or until core temperature returns to normal values ( ̴ 36.5-37˚C).

A. Spontaneous rewarming (Shivering Only) - In this control condition, no external heat will be provided and you will rewarm spontaneously with the heat produced from shivering.

B. Head Warming (Head): Either of these rewarming methods will be used:

• Forced-Air Warming to the Head (FAW-H) - A modified rigid forced-air warming cover will be placed over your head. Warm air ( ̴43˚C) will blow into the cover through an inlet on top of the cover and will escape from the bottom of the cover. You will be breathing warm air (̴ 43˚C).
• Charcoal Heater to the Head (CH-H) - A charcoal heater will be placed on right side of your face/head with ducts wrapping around the dorsum of the head, anteriorly over the forehead, nose, chin and the neck, not covering the eyes or the mouth. You will be breathing ambient air (̴ 22˚C).

C. Torso Warming - Either of these rewarming methods will be used:

• Forced-Air Warming to the Torso (FAW-T) - A specially designed portable rigid forced-air cover (PORIFAC) will be placed over your torso and the upper thighs. Warm air (̴ 43˚C) will blow into the cover through an inlet above the abdomen and will escape from the bottom of the cover. Participant will be breathing ambient air (̴ 22˚C).
• Charcoal Heater to the Torso (CH-T) - The charcoal heater will be placed on your anterior chest with a towel in between. The flexible ducts will be applied to the areas of high heat transfer i.e. over the shoulders, neck, and then anteriorly under the axillae to cross over the lower anterior chest. You will be breathing ambient air at room temperature (~22˚C).

After 60 minutes of warming, subjects will be placed in a warm water bath (40-42˚C) until they are comfortable and core temperature returns to normal values (̴ 36.5-37˚C).

Outcome measures include rate of core cooling, afterdrop amount, rate of rewarming, skin heat flux, oxygen consumption and shivering intensity.

• Study Type: Interventional
• Enrollment (Actual): 7
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Manitoba
    • Winnipeg, Manitoba, Canada, R3T 2N2
      • University of Manitoba

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 45 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• 18-45 yrs old, males or females, healthy

Exclusion Criteria:

• cardiopulmonary disease
• any symptoms caused by cold exposure

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Rate of body core rewarming	Esophageal temperature will be used to determine the rate of core temperature rewarming during 60 minutes of rewarming via either shivering only, or external heat donated to the torso or the head.	60 minutes

Collaborators and Investigators

• Sponsor: University of Manitoba
• Investigators: Principal Investigator: Gordon G Giesbrecht, Ph.D., University of Manitoba

Study record dates

Study Major Dates

• Study Start: June 1, 2012
• Primary Completion (Actual): December 1, 2012
• Study Completion (Actual): December 1, 2012

Study Registration Dates

• First Submitted: May 18, 2012
• First Submitted That Met QC Criteria: May 21, 2012
• First Posted (Estimate): May 23, 2012

Study Record Updates

• Last Update Posted (Estimate): April 8, 2013
• Last Update Submitted That Met QC Criteria: April 4, 2013
• Last Verified: April 1, 2013

More Information

Terms related to this study

• Keywords: hypothermia; rewarming; core cooling; afterdrop; pre-hospital treatment
• Additional Relevant MeSH Terms: Body Temperature Changes; Hypothermia; Physiological Effects of Drugs; Protective Agents; Antidotes; Charcoal
• Other Study ID Numbers: B2012:024; NSERC PIN (Other Grant/Funding Number: NSERC PIN)