Cerebral Oximetry in Lower Body Negative Pressure

NCT ID: NCT03009305

Last Updated: 2017-03-17

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 20 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2015-10-31
• Study Completion Date: 2017-03-31

Brief Summary

The study aims to describe hemodynamic effects of lower body negative pressure (LBNP).

1. If and how changes in cerebral oxygen saturation (StO2) measured by near infrared spectroscopy (NIRS) relate to changes in blood flow in the carotid arteries during progressive LBNP.

2. If and how mean systemic filling pressure (MSFP) can be measured by brief occlusion of blood flow to an arm and if this relates to LBNP-level.

3. If and how pulse pressure variations and photoplethysmographic amplitude variations during positive expiratory pressure (PEP) and continuous positive airway pressure (CPAP) relate to LBNP-level.

Detailed Description

20 healthy volunteers will be included. The study protocol consists of two parts.

1. LBNP is applied stepwise (20 mmHg increments). At each LBNP-level, after 2 min stabilization, blood flow in internal and external carotid arteries is measured. Thereafter, MSFP is measured. LBNP is applied to -80 mmHg, but terminated sooner if the subject experiences signs of decompensation.

Changes in cerebral StO2 will be related to relative changes in blood flow in the carotid arteries. After these measurements, blood flow to one arm will be occluded for 30 s. Venous pressure measured in an antecubital vein approximates MSFP. This will be related to volume status (LBNP-level and stroke volume reduction).

2. LBNP is applied stepwise (20 mmHg increments). At each LBNP-level, after 2 min stabilization, PEP and CPAP are applied at 0, 5 and 10 cmH20. LBNP is applied to -80 mmHg, but terminated sooner if the subject experiences signs of decompensation.

Flow in carotid arteries is measured by ultrasound/Doppler. Skin blood flow in the forehead measured by laser Doppler flowmetry and transcutaneous oxygen saturation.

If possible, blood flow velocity in a. cerebri media will be measured by transcranial Doppler.

Central venous pressure will be approximated by measuring pressure in the left subclavian vein ("half-way" catheter).

Cardiac stroke volume will be measured by suprasternal Doppler. Expiratory carbon dioxide (CO2) will be measured and recorded. Acral skin photoplethysmography performed using proprietary and custom-made photoplethysmographs.

Arterial blood pressure approximated by finger volume-clamp method.

The measurements above will be used for analyses of possible physiological mechanisms and post-hoc analyses.

Conditions

Hypovolemia

Study Design

• Allocation Method: NA
• Intervention Model: SINGLE_GROUP
• Primary Study Purpose: DIAGNOSTIC
• Blinding Strategy: NONE

Study Groups

Lower body negative pressure

Single-arm, lower body negative pressure, continuous positive airway pressure, positive expiratory pressure.

Group Type: EXPERIMENTAL

Lower body negative pressure

Intervention Type: OTHER

Model of hypovolemia: Lower body negative pressure down to -80 mmHg (maximum).

Continuous positive airway pressure

Intervention Type: DEVICE

CPAP of 0, 5 and 10 cm water (H2O).

Positive expiratory pressure

Intervention Type: DEVICE

PEP of 0, 5 and 10 cm H2O.

Interventions

Lower body negative pressure

Model of hypovolemia: Lower body negative pressure down to -80 mmHg (maximum).

Intervention Type: OTHER

Continuous positive airway pressure

CPAP of 0, 5 and 10 cm water (H2O).

Intervention Type: DEVICE

Positive expiratory pressure

PEP of 0, 5 and 10 cm H2O.

Intervention Type: DEVICE

Other Intervention Names

CPAP; PEP

Eligibility Criteria

Inclusion Criteria

• Healthy volunteer (informed consent)

Exclusion Criteria

• Disease/physical condition limiting normal physical activity or requiring medication (except allergies/contraceptives)
• History of syncope (except with obvious vasovagal etiology)
• Cardiac arrhythmia
• Pregnancy
• Skin infections in the elbow crease

• Minimum Eligible Age: 18 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Oslo University Hospital

OTHER

Sponsor Role: lead

Responsible Party

Svein Aslak Landsverk

MD, PhD

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Svein Aslak Landsverk, M.D., PhD

Role: PRINCIPAL_INVESTIGATOR

Oslo University Hospital

Locations

Oslo University Hospital

Oslo, Oslo County, Norway

Countries

Norway

Other Identifiers

2015/3995

Identifier Type: -

Identifier Source: org_study_id