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Active, Not Recruiting

NCT Number: NCT06279897

LBNP Tolerance With Skin Warming After Exercise Cold Stress

Assess the effect of skin rewarming during lower body negative pressure upon arterial blood pressure and tolerance to simulated blood loss after exercise in the cold.

Active, Not Recruiting

This study is active but is not currently recruiting participants.

Key information

Conditions

Blood Pressure Blood Loss Hemorrhage Pathologic Processes Pathological Conditions, Signs and Symptoms

Age range

18 year–40 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

University of Colorado Colorado Springs

Colorado Springs, Colorado, 80918, United States

About this study

Individuals who have experienced a hemorrhagic insult are often wrapped in a warm blanket. In individuals who have exercise in a cold environment, it is unknown how this skin warming influence tolerance to simulated blood loss and whether there is an optimal temperature to warm the skin up to in order to lower blood pressure (permissive hypotension).

After an initial study visit to examine exercise capacity (Visit 1), participants will complete four trials (Visits 2 through 5) After exercise in a cold environment, participants will have cold skin temperatures (~82°F; Visit 2). Researchers will examine how increasing skin temperature to normal (~90°F; Visit 3), warm (93°F; Visit 4) and hot (95°F; Visit 5) influences arterial blood pressure and tolerance to simulated blood loss compared to when the skin remains cold.

This project will test the hypothesis that skin rewarming to ~95°F lowers arterial blood pressure without impairing tolerance to simulated blood loss (lower body negative pressure; LBNP) relative to when the skin is kept cold (82°F).

Primary data include core and skin temperatures, arterial blood pressure and LBNP tolerance time. Secondary variables include skin blood flow and heart rate. After completing visit 1 first, all participants will complete visits 2 through 5 in a randomized order and participants are blinded. The order will be counterbalanced between participants.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • 18 and 40 years old
  • free of known disease and illness
  • Speak English
  • Systolic blood pressure <140mmHg
  • Diastolic blood pressure <90 mmHg

Exclusion criteria

  • Currently pregnant or breast feeding
  • Individuals with diagnosed with cardiac, respiratory, neurological and/or metabolic illness or disease.
  • Currently taking prescribed or over the counter medications known to influence the cardiovascular, pulmonary, renal and/or central nervous system.
  • Current use of tobacco or nicotine products
  • Any physical limitations that impede completion of the tests, such as exercise tests will also be an exclusion criteria.
  • Body mass< 80 pounds body weight
  • Appendectomy

Treatment and study plan

Skin Surface Rewarming

Other

Sixty seconds after the onset of lower body negative pressure (LBNP) skin temperature will be increased to ~90°F and held here for the duration of the LBNP test.

Other names: Normothermic Trial

Skin Surface Warming

Other

Sixty seconds after the onset of lower body negative pressure (LBNP) skin temperature will be increased to ~93°F and held here for the duration of the LBNP test.

Other names: Warm Trial

Skin Surface Heating

Other

Sixty seconds after the onset of lower body negative pressure (LBNP) skin temperature will be increased to ~95°F and held here for the duration of the LBNP test.

Other names: Hot Trial

Skin Surface Cooling

Other

Sixty seconds after the onset of lower body negative pressure (LBNP) skin temperature will remain lowered to ~82°F for the duration of the LBNP test.

Other names: Cold Trial, Control Trial

Primary outcomes

  1. Arterial blood pressure

    Time frame: Before and during lower body negative pressure (LBNP) procedure

    During simulated blood loss is the reduction in arterial blood pressure greater with progressive skin heating

  2. Tolerance to simulated blood loss

    Time frame: Lower body negative pressure test duration in all trials.

    Tolerance to LBNP will be quantified using the cumulative stress index (CSI) calculated by summing the time at each level of LBNP multiplied by that level (i.e., 20 mmHg * 3 min + 30 mmHg * 3 min + 40 mmHg * 3 min, etc.) until test termination.

Secondary outcomes

  1. Core temperature

    Time frame: Throughout exercise cold exposure and continuously during LBNP

    Measured using rectal probe or intestinal pill and indicative of change in internal body temperature.

  2. Cutaneous Vascular Conductance

    Time frame: Before and during lower body negative pressure (LBNP) procedure

    Skin blood flow measured using laser Doppler flowmetry (AU) will be referenced relative to arterial blood pressure (mmHg) and expressed as cutaneous vascular conductance (CVC; AU/mmHg)

Sponsors and collaborators

Lead sponsor

University of Colorado, Colorado Springs

Other

Registry information

Official study title

Skin Rewarming After Exercise Cold Stress and Tolerance to Simulated Blood Loss

Important dates

Study start
2022
Primary completion
2026
Study completion
2026
First posted
Feb 28, 2024
Registry last updated
Mar 27, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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