Blood Loss, Blood Pressure
Conditions
Keywords
Arterial Blood Pressure, Permissive Hypotension, Cold Stress, Skin Warming, Blood Loss
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.
Interventions
OTHERSkin Surface Rewarming
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.
OTHERSkin Surface Warming
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.
OTHERSkin Surface Heating
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.
OTHERSkin Surface Cooling
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.
Sponsors
University of Colorado, Colorado Springs
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE
Masking description
Participants are blinded to the skin temperature control.
Intervention model description
Participants will complete trial 1 at the beginning of the study. Participants will then complete trials 2 through 5 in a random, counterbalanced order.
Eligibility
Sex/Gender
ALL
Age
18 Years to 40 Years
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| 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
| Measure | Time frame | Description |
|---|---|---|
| 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) |
Countries
United States
Outcome results
None listed