Recruiting

Observational Study

Sponsor:

University of Calgary

Code:

NCT05295810

Conditions

Orthostatic Hypotension

Neurogenic Orthostatic Hypotension

Eligibility Criteria

Sex: All

Age: 18 - 70+

Healthy Volunteers: Accepted

Interventions

Sequential Gas Delivery

Study Details

Brief summary:

The Autonomic (or "automatic") Nervous System (ANS) regulates internal processes, including control of heart rate and blood pressure (BP). When someone stands, and gravity tries to pull blood away from the brain, the ANS works to maintain BP and brain blood flow. Neurogenic Orthostatic Hypotension (NOH) occurs when our "fight-or-flight" part ("sympathetic") of the ANS fails. BP can drop a lot when upright, reducing blood flow and oxygen delivery to the brain, and this can cause symptoms of light-headedness, nausea, and fainting.

One solution to help counter the effects of NOH may be to increase sympathetic activity by breathing higher levels of carbon dioxide. In healthy volunteers, small increases in the amount of inhaled carbon dioxide has been shown to increase BP in the upright position, and this improves symptoms!

The objectives of the current study are to apply carbon dioxide in patients with NOH and healthy controls to: (a) evaluate the effects of breathing carbon dioxide on BP and brain blood flow, and (b) determine if a device that increases carbon dioxide while standing will work as a new therapy

Conditions

Orthostatic Hypotension

Neurogenic Orthostatic Hypotension

Study ID

NCT05295810

Start date

Mar 1, 2022

Status verified date

Apr, 2026

Completion date

May 31, 2030

Anticipated

Primary completion date

Dec 31, 2029

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18 - 70+

Healthy Volunteers: Accepted

Inclusion Criteria:

  • Age ≥18 years
  • Male and Female
  • Non - smokers.
  • Able and willing to provide informed consent.
  • Ability to travel to Libin Cardiovascular Institute Autonomic Testing Lab at the University of Calgary, Calgary, AB.

Exclusion Criteria:

  • Medical therapies or medications which could interfere with testing of autonomic function
  • Participants with somatization or severe anxiety symptoms will be excluded
  • Pregnant or breast-feeding females
  • Inability to tolerate mask for the duration of the study
  • Subjects who require portable oxygen at rest or with exercise
  • Subjects with chronic heart failure or severe pulmonary disease who are unable to climb one flight of stairs due to shortness of breath.
  • Presence of failure of other organ systems or systemic illness that can affect autonomic function or the participant's ability to cooperate. These include: dementia, alcohol and/or drug abuse, cerebrovascular disease, kidney or liver disease, surgical procedures where the nerves of the sympathetic nervous system have been cut.
  • Other factors which in the investigator's opinion would prevent the participant from completing the protocol, including poor compliance during previous studies.

Study Design

Enrollment

80 participants

Anticipated

Allocation

Randomized

Intervention Model

Crossover

Primary purpose

Treatment

Interventions and Outcome Measures

Arms

no intervention: Room Air

All participants will complete an active stand breathing room air with CO2 free to fluctuate

experimental: +0mmHg CO2 Clamped at baseline

All participants will complete an active stand with their CO2 held constant at baseline

experimental: +5mmHg CO2

All participants will complete an active stand breathing +5mmHg of CO2 relative to baseline

experimental: +10mmHg

All participants will complete an active stand breathing +10mmHg of CO2 relative to baseline

experimental: +10mmHg CO2 + 50mmHg O2

All participants will complete an active stand breathing +10mmHg of CO2 relative to baseline and 50mmHg of O2

Interventions

Sequential Gas Delivery

Sequential Gas Delivery will be controlled using the RespirAct™ system (Thornhill Research Inc., Toronto, Canada)

Primary outcome measure

  • Δ Blood Pressure (BP) [ Time Frame: The ΔBP (stand-sit) calculated as the average BP in the final minute of sitting and the average BP between minute 3 and 5 of stand will be compared between room air and +10mmHg of CO2 ]

Central Contacts and Locations

Central contacts

Jacquie Baker, PhD

4032103819jacquie.baker@ucalgary.ca

Rasha Hamzeh, RN

autonomic.research@ucalgary.ca

Locations

University of Calgary

Recruiting

Calgary, Alberta, Canada

Contacts

Satish R Raj, MD

403-210-6152autonomic.research@ucalgary.ca

Robert S Sheldon, MD, PhD

403-220-8191autonomic.research@ucalgary.ca

More Information

Sponsor

University of Calgary

Last update posted

May 5, 2026

Last verified

Apr, 2026

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-10. This information was provided to ClinicalTrials.gov by University of Calgary on 2026-05-05.