LBNP Tolerance With Skin Warming After Exercise Cold Stress

Not Applicable

Active, not recruiting

• Conditions: Blood Loss; Blood Pressure
• Interventions: Other: Skin Surface Rewarming; Other: Skin Surface Warming; Other: Skin Surface Heating; Other: Skin Surface Cooling

• Registration Number: NCT06279897
• Lead Sponsor: University of Colorado, Colorado Springs

Brief Summary

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.

Detailed Description

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.

Study Timeline

• Study Start: 2022-01-24
• Study First Submitted: 2024-02-07
• Study First Submitted QC: 2024-02-22
• Study First Posted: 2024-02-28
• Status Verified: 2025-03
• Last Update Submitted: 2025-03-26
• Last Update Posted: 2025-03-27
• Primary Completion: 2026-09-30
• Study Completion: 2026-09-30

Recruitment & Eligibility

• Status: ACTIVE_NOT_RECRUITING
• Sex: All
• Target Recruitment: 10

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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
Skin Temperature Control During Simulated Blood Loss After Exercise Cold Stress	Skin Surface Rewarming	After exercise in the cold and participants skin will remain cold (\~82°F), be returned to normal (\~90°F), be slightly warmed (\~93°F) or heated (\~95°F) sixty seconds after the onset of LBNP.
Skin Temperature Control During Simulated Blood Loss After Exercise Cold Stress	Skin Surface Cooling	After exercise in the cold and participants skin will remain cold (\~82°F), be returned to normal (\~90°F), be slightly warmed (\~93°F) or heated (\~95°F) sixty seconds after the onset of LBNP.
Skin Temperature Control During Simulated Blood Loss After Exercise Cold Stress	Skin Surface Heating	After exercise in the cold and participants skin will remain cold (\~82°F), be returned to normal (\~90°F), be slightly warmed (\~93°F) or heated (\~95°F) sixty seconds after the onset of LBNP.
Skin Temperature Control During Simulated Blood Loss After Exercise Cold Stress	Skin Surface Warming	After exercise in the cold and participants skin will remain cold (\~82°F), be returned to normal (\~90°F), be slightly warmed (\~93°F) or heated (\~95°F) sixty seconds after the onset of LBNP.

Primary Outcome Measures

Name	Time	Method
Arterial blood pressure	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
Tolerance to simulated blood loss	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 Outcome Measures

Name	Time	Method
Core temperature	Throughout exercise cold exposure and continuously during LBNP	Measured using rectal probe or intestinal pill and indicative of change in internal body temperature.
Cutaneous Vascular Conductance	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)

Trial Locations

Locations (1)

University of Colorado Colorado Springs; 🇺🇸 Colorado Springs, Colorado, United States