Recruiting

CO2

Sponsor:

University of Calgary

Code:

NCT04271878

Conditions

Postural Tachycardia Syndrome

Orthostatic Intolerance

Eligibility Criteria

Sex: All

Age: 18 - 60

Healthy Volunteers: Not accepted

Interventions

RespirAct™ system (Thornhill Research Inc., Toronto, Canada)

Study Details

Brief summary:

The mechanism behind postural orthostatic tachycardia syndrome (POTS) involves many causes including a sympathetic nervous system problem. Blood gases, like carbon dioxide (CO2), have an important effect on sympathetic activation.

The purpose of this research study is to determine if higher CO2 levels have any effect in lowering heart rate and reducing POTS symptoms when upright/standing. The investigators are also searching for the ideal CO2 concentration to achieve the most effective response

Conditions

Postural Tachycardia Syndrome

Orthostatic Intolerance

Study ID

NCT04271878

Start date

Feb 2, 2022

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 - 60

Healthy Volunteers: Not accepted

Inclusion Criteria:

  • Physician diagnosis of Postural Tachycardia Syndrome (POTS)
  • Age 18-60 years
  • Male and Female
  • Non - smokers.
  • Able and willing to provide informed consent.
  • Ability to travel to Libin Cardiovascular Institute of Alberta Autonomic Testing Lab at the University of Calgary, Calgary, AB.

Exclusion Criteria:

  • Overt cause for postural tachycardia, i.e., acute dehydration
  • Participants with somatization or severe anxiety symptoms will be excluded
  • Pregnant
  • 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.
  • 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

26 participants

Anticipated

Intervention Model

Single group

Primary purpose

Other

Interventions and Outcome Measures

Arms

other: All participants

All participants will receive the same interventions

Interventions

RespirAct™ system (Thornhill Research Inc., Toronto, Canada)

1. HUTT with Normal Breathing in Room Air (No gas interventions will be applied)
2. HUTT with Normal Breathing and ETCO2 clamped at baseline levels
3. HUTT with Normal Breathing and Mild Hypercapnia (the ETCO2 will be clamped at 45mmHg )
4. HUTT with Normal Breathing and High Hypercapnia (the ETCO2 will be clamped at 55mmHg)
5. HUTT with Fast, Deep Breathing and resultant Hypocapnia Participant will be coached to breath around 15 breath per min.No gas interventions will be applied
6. HUTT with Fast, Deep Breathing and ETCO2 clamped at baseline levels. Participant will be coached to breath around 15 breath per min, with ETCO2 clamped to baseline levels.

Primary outcome measure

  • Heart Rate (HR) variation [ Time Frame: difference between HR from supine to peak HR during tilt test for each intervention (mean value HR between the 8th and 9th minute of supine; peak parameters, during HUTT, mean value during the first min and between the 3rd and 8th min) ]

Central Contacts and Locations

Central contacts

Shaun Ranada, BSc

403-210-6152shaun.ranada@ucalgary.ca

Rasha Hamza, RN

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

Locations

University of Calgary

Recruiting

Calgary, Alberta, Canada, T2N 4Z6

Contacts

Satish R Raj, MD MSCI

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 7, 2026

Last verified

Apr, 2026

Keywords

  • postural tachycardia
  • autonomic
  • orthostatic intolerance
  • dysautonomia

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 2026-05-07.