Recruiting

CO2 Rebreathing

Sponsor:

University of Calgary

Code:

NCT05908760

Conditions

Neurogenic Orthostatic Hypotension

Autonomic Failure

Eligibility Criteria

Sex: All

Age: 18 - 70+

Healthy Volunteers: Not accepted

Interventions

CO2 ReHaler

Study Details

Brief summary:

Neurogenic orthostatic hypotension (nOH) is a chronic condition associated with increased cardiovascular risk and reduced quality of life. On standing, patients with nOH experience a large reduction in blood pressure (BP; at least ≥20/10mmHg, but often much more), which is often accompanied by debilitating symptoms and syncope. A previous study (unpublished) showed that hypercapnia significantly increases standing BP in patients with nOH. Human bodies naturally produce and exhale CO2. Rebreathe devices offer a simple, cost-effective technology to increase arterial CO2. In brief, rebreathe devices work by capturing expired CO2, which is then re-inhaled. The net effect is a transient increase in CO2. A CO2 rebreathing device may offer a novel hemodynamic therapy for patients with nOH.

This is a pilot, proof-of-concept study to evaluate a CO2 rebreather to improve blood pressure and orthostatic tolerance in patients with nOH. The hypothesis is that a rebreather will increase CO2 sufficiently enough to improve BP in patients with nOH.

Male and female patients (n=28) will be asked to complete two randomized 70° head-up tilt (HUT) tests breathing either room air or using a CO2 rebreather. Hemodynamics (BP, heart rate, stroke volume, brain blood flow) and orthostatic symptoms will be assessed throughout. Breath-by-breath data will include O2, CO2, respiration rate and tidal volume.

The primary outcome measure will be the magnitude of the BP response (ΔBP = HUT - Supine) during Room Air vs. Hypercapnia. The primary outcome will be compared between room air and hypercapnia using a paired t-test.

Conditions

Neurogenic Orthostatic Hypotension

Autonomic Failure

Study ID

NCT05908760

Start date

Jul 30, 2024

Status verified date

Apr, 2026

Completion date

Dec 31, 2030

Anticipated

Primary completion date

Dec 31, 2029

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18 - 70+

Healthy Volunteers: Not accepted

Inclusion Criteria:

  • Age ≥18 years
  • Male and Female
  • Physician diagnosis of Neurogenic Orthostatic Hypotension
  • 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
  • Pregnant or breast-feeding females
  • 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

28 participants

Anticipated

Allocation

Randomized

Intervention Model

Crossover

Primary purpose

Treatment

Interventions and Outcome Measures

Arms

experimental: CO2 Rebreathing

Participants will breathe with the rebreather in the supine position until CO2 levels increase between 5-10mmHg. Once CO2 levels are increased, participants will be tilted upright, and will continue to breathe with the rebreather during a 5-min HUT test

no intervention: Room Air

Participants will breathe room air in the supine position and during a 5-min HUT test

Interventions

CO2 ReHaler

The ReHaler captures expired CO2, which is then re-inhaled. The net effect is a transient increase in CO2.

Primary outcome measure

  • Δ Blood Pressure (BP) [ Time Frame: The ΔBP (HUT-Supine) calculated as the average BP in the final two minutes of supine baseline and the average BP between minute 3 and 5 of HUT will be compared between room air and CO2 rebreathe ]

Central Contacts and Locations

Central contacts

Jacquie Baker, PhD

4032103819autonomic.research@ucalgary.ca

Angela Qi, MD

4032107627autonomic.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.