VasodilationNCT05001048
Sex Differences in Sympathetic Activity and Vascular Reactivity During Acute and Chronic Hypoxia.
A study testing Phenylephrine Hydrochloride, Cold Pressor Test and Isocapnic Acute Hypoxia in people with Vasodilation and Vasoconstriction, run by University of Alberta at 2 sites in Canada.
Trial summary
This study aims to investigate sex differences in blood pressure control associated with exposure to acute hypoxia (low oxygen), and short term acclimatization to hypoxia at high altitude. Read more about this study
- Who is it for?
- Ages 18 to 50 yearsHealthy volunteers can take part
- Conditions the study is for
- Vasodilation, Vasoconstriction
- What is being tested?
- Phenylephrine Hydrochloride, Cold Pressor Test and Isocapnic Acute Hypoxia
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 14 participants
- Where
- 2 sitesCanada
- Study dates
- 4 Aug 2019to 9 Sep 2022
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 50 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Between ages of 18-50
- No medical history of cardiovascular, respiratory, nervous system, or metabolic disease
- Females must be pre-menopausal
Who cannot join
- Any known cardiovascular, respiratory, nervous system, or metabolic disease (however, participants with controlled arterial hypertension will not be excluded)
- Having travelled above 2,000m within 1 month of testing at low and high altitude
- Females who are pregnant, confirmed by a pregnancy test
- Females who are post-menopausal
- Participants that are classified as obese (body mass index > 30kg⋅m²)
- Have a history of smoking regularly in the last 6 months (but nicotine substitutes (patch, gum) not an exclusion criteria)
- Those with a known allergy to sulfites
- Participants taking monoamine oxidase (MAO) inhibitors or tricyclic antidepressants
Trial locations and contacts
2 sites in 1 country.
Canada2 sites
Mount Royal University
Calgary, Alberta, T3E 6K6
University of Alberta
Edmonton, Alberta, T6G 2R3
About this study
This study aims to investigate sex differences in blood pressure control associated with exposure to acute hypoxia (low oxygen), and short term acclimatization to hypoxia at high altitude.
Read the detailed description
About 200 million people worldwide live at high altitudes. Millions of others travel to high altitude every year for work or travel. The low oxygen (or hypoxia) experienced at high altitudes causes considerable physiological stress, and the body adapts in order to maintain adequate oxygen delivery to its tissues. One of these adaptations is an increase in the activity of the sympathetic nervous system. This system is responsible for the "fight or flight" response. Sympathetic activity regulates the size of the blood vessels, which will affect blood pressure. Previous studies suggest that males and females regulate their blood pressure in different ways. Females tend to have lower resting sympathetic activity, and less vasoconstriction in response to stressors than males. Blood pressure changes are also influenced by levels of sex hormones; for example, estrogen may cause opposing vasodilation. Therefore, it is important to understand the differences in how males and females respond to low oxygen.
The main purpose of this study is to examine the differences between males and females in control of blood vessels during exposure to low oxygen. To study this question, we will test vasoreactivity to set physiological stressors in both males and females. Participants will be recruited at the Canadian sites, and we will test them while they breathe low oxygen for a short amount of time at low altitude. We will also perform assessments on the same participants during a two week stay at high altitude at White Mountain, CA, which is at an altitude of 3,800m. These data will have implications in the basic understanding of differences between male and female physiology. Specifically, to males and females living or travelling to high altitude.
- Conditions
- Vasodilation, Vasoconstriction
- Being tested
- Phenylephrine Hydrochloride, Cold Pressor Test, Isocapnic Acute Hypoxia, Hyperoxia
- Medical subject headings
- Aneurysm
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Phenylephrine HydrochlorideDrug
Also called Neo-Synephrine
Series of three incremental bolus injections to observe α1-adrenoreceptor mediated vasoconstriction.
Cold Pressor TestOther
Standardized sympathetic stressor involving submersion of the hand in ice-cold water for 3-minutes, aiming to elicit endogenous neurotransmitter release and blood pressure increases.
Isocapnic Acute HypoxiaOther
During low altitude assessment, participants will be exposed to isocapnic hypoxia equivalent to 3,800m to assess responses to acute exposure.
HyperoxiaOther
During high altitude assessments, participants will breathe an oxygen concentration comparable to their end-tidal values at low altitude for the assessment of the influences of acclimatization.
| Study group | Role | What they receive |
|---|---|---|
| Low Altitude | Experimental | Participants will be assessed at an altitude of <1050m. Receives: Drug: Phenylephrine Hydrochloride; Other: Cold Pressor Test; Other: Isocapnic Acute Hypoxia |
| Early Acclimatization to High Altitude | Experimental | Participants will be assessed on day 2 or 3 of a high-altitude expedition at 3,800m. Receives: Drug: Phenylephrine Hydrochloride; Other: Cold Pressor Test; Other: Hyperoxia |
| Late Acclimatization to High Altitude | Experimental | Participants will be assessed on day 9 or 10 of a high-altitude expedition at 3,800m. Receives: Drug: Phenylephrine Hydrochloride; Other: Cold Pressor Test; Other: Hyperoxia |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in blood pressure
Phenylephrine sensitivity
Measured: 18 minutes
Change in arterial blood flow
Phenylephrine sensitivity
Measured: 18 minutes
Cold pressor test reactivity
Measured: 4 minutes
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted11 Aug 2021
- Study start4 Aug 2019
- Primary completion7 Dec 2021
- Study completion9 Sep 2022
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (4)Papers the sponsor has linked to this study.
- Other trials for VasodilationStudies of the same condition, open and under way.
- More trials run by University of AlbertaThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Crossover
- Model description
- Participants will partake in all three arms of the study, which include: 1) low altitude, 2) early acclimatization, and 3) late acclimatization to high altitude assessments.
- Masking
- None (open label)
- Enrolment
- 14 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Alberta
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Sean van Diepen, MD, MSc, Principal investigator, University of AlbertaCraig Steinback, PhD, Principal investigator, University of Alberta
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05001048
- Sponsor's protocol ID
- Pro00088122
- Status last verified
- Oct 2022
- First submitted
- 4 Aug 2021
- Last updated
- 31 Oct 2022
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
Publications
Hart EC, Charkoudian N, Wallin BG, Curry TB, Eisenach JH, Joyner MJ. Sex differences in sympathetic neural-hemodynamic balance: implications for human blood pressure regulation. Hypertension. 2009 Mar;53(3):571-6. doi: 10.1161/HYPERTENSIONAHA.108.126391. Epub 2009 Jan 26.
PubMed 19171792Mazzeo RS, Child A, Butterfield GE, Mawson JT, Zamudio S, Moore LG. Catecholamine response during 12 days of high-altitude exposure (4, 300 m) in women. J Appl Physiol (1985). 1998 Apr;84(4):1151-7. doi: 10.1152/jappl.1998.84.4.1151.
PubMed 9516178Purdy GM, James MA, Rees JL, Ondrus P, Keess JL, Day TA, Steinback CD. Spleen reactivity during incremental ascent to altitude. J Appl Physiol (1985). 2019 Jan 1;126(1):152-159. doi: 10.1152/japplphysiol.00753.2018. Epub 2018 Nov 21.
PubMed 30462566Usselman CW, Gimon TI, Nielson CA, Luchyshyn TA, Coverdale NS, Van Uum SH, Shoemaker JK. Menstrual cycle and sex effects on sympathetic responses to acute chemoreflex stress. Am J Physiol Heart Circ Physiol. 2015 Mar 15;308(6):H664-71. doi: 10.1152/ajpheart.00345.2014. Epub 2014 Dec 19.
PubMed 25527774
Study at a glance
From the registry record, last updated by the sponsor on 31 Oct 2022. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Sex Differences in Sympathetic Activity and Vascular Reactivity During Acute and Chronic Hypoxia.
- ClinicalTrials.gov ID
- NCT05001048
- Acronym / sponsor ID
- Pro00088122
- Conditions
- Vasodilation, Vasoconstriction
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 14 participants (actual)
- Lead sponsor
- University of AlbertaUniversity, hospital or other
- Study start
- 4 Aug 2019 (actual)
- Primary completion
- 7 Dec 2021 (actual)
- Study completion
- 9 Sep 2022 (actual)
- First posted
- 11 Aug 2021 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study aims to investigate sex differences in blood pressure control associated with exposure to acute hypoxia (low oxygen), and short term acclimatization to hypoxia at high altitude.
Detailed description
About 200 million people worldwide live at high altitudes. Millions of others travel to high altitude every year for work or travel. The low oxygen (or hypoxia) experienced at high altitudes causes considerable physiological stress, and the body adapts in order to maintain adequate oxygen delivery to its tissues. One of these adaptations is an increase in the activity of the sympathetic nervous system. This system is responsible for the "fight or flight" response. Sympathetic activity regulates the size of the blood vessels, which will affect blood pressure. Previous studies suggest that males and females regulate their blood pressure in different ways. Females tend to have lower resting sympathetic activity, and less vasoconstriction in response to stressors than males. Blood pressure changes are also influenced by levels of sex hormones; for example, estrogen may cause opposing vasodilation. Therefore, it is important to understand the differences in how males and females respond to low oxygen.
The main purpose of this study is to examine the differences between males and females in control of blood vessels during exposure to low oxygen. To study this question, we will test vasoreactivity to set physiological stressors in both males and females. Participants will be recruited at the Canadian sites, and we will test them while they breathe low oxygen for a short amount of time at low altitude. We will also perform assessments on the same participants during a two week stay at high altitude at White Mountain, CA, which is at an altitude of 3,800m. These data will have implications in the basic understanding of differences between male and female physiology. Specifically, to males and females living or travelling to high altitude.
Study design
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 3
- Model description
- Participants will partake in all three arms of the study, which include: 1) low altitude, 2) early acclimatization, and 3) late acclimatization to high altitude assessments.
| Arm | Type | Receives |
|---|---|---|
| Low Altitude | Experimental | Drug: Phenylephrine Hydrochloride, Other: Cold Pressor Test, Other: Isocapnic Acute HypoxiaParticipants will be assessed at an altitude of <1050m. |
| Early Acclimatization to High Altitude | Experimental | Drug: Phenylephrine Hydrochloride, Other: Cold Pressor Test, Other: HyperoxiaParticipants will be assessed on day 2 or 3 of a high-altitude expedition at 3,800m. |
| Late Acclimatization to High Altitude | Experimental | Drug: Phenylephrine Hydrochloride, Other: Cold Pressor Test, Other: HyperoxiaParticipants will be assessed on day 9 or 10 of a high-altitude expedition at 3,800m. |
Who may qualify
- Ages
- 18 to 50 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (3 listed)
- Between ages of 18-50
- No medical history of cardiovascular, respiratory, nervous system, or metabolic disease
- Females must be pre-menopausal
Key exclusion criteria (8 listed)
- Any known cardiovascular, respiratory, nervous system, or metabolic disease (however, participants with controlled arterial hypertension will not be excluded)
- Having travelled above 2,000m within 1 month of testing at low and high altitude
- Females who are pregnant, confirmed by a pregnancy test
- Females who are post-menopausal
- Participants that are classified as obese (body mass index > 30kg⋅m²)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Phenylephrine HydrochlorideAlso: Neo-SynephrineSeries of three incremental bolus injections to observe α1-adrenoreceptor mediated vasoconstriction. | Drug | Early Acclimatization to High Altitude, Late Acclimatization to High Altitude, Low Altitude |
| Cold Pressor TestStandardized sympathetic stressor involving submersion of the hand in ice-cold water for 3-minutes, aiming to elicit endogenous neurotransmitter release and blood pressure increases. | Other | Early Acclimatization to High Altitude, Late Acclimatization to High Altitude, Low Altitude |
| Isocapnic Acute HypoxiaDuring low altitude assessment, participants will be exposed to isocapnic hypoxia equivalent to 3,800m to assess responses to acute exposure. | Other | Low Altitude |
| HyperoxiaDuring high altitude assessments, participants will breathe an oxygen concentration comparable to their end-tidal values at low altitude for the assessment of the influences of acclimatization. | Other | Early Acclimatization to High Altitude, Late Acclimatization to High Altitude |
Primary outcome
Change in blood pressure
Time frame: 18 minutes
Phenylephrine sensitivity
Change in arterial blood flow
Time frame: 18 minutes
Phenylephrine sensitivity
Cold pressor test reactivity
Time frame: 4 minutes
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 31 Oct 2022.
- Background: PubMed 19171792Hart EC, Charkoudian N, Wallin BG, Curry TB, Eisenach JH, Joyner MJ. Sex differences in sympathetic neural-hemodynamic balance: implications for human blood pressure regulation. Hypertension. 2009 Mar;53(3):571-6. doi: 10.1161/HYPERTENSIONAHA.108.126391. Epub 2009 Jan 26.
- Background: PubMed 9516178Mazzeo RS, Child A, Butterfield GE, Mawson JT, Zamudio S, Moore LG. Catecholamine response during 12 days of high-altitude exposure (4, 300 m) in women. J Appl Physiol (1985). 1998 Apr;84(4):1151-7. doi: 10.1152/jappl.1998.84.4.1151.
- Background: PubMed 30462566Purdy GM, James MA, Rees JL, Ondrus P, Keess JL, Day TA, Steinback CD. Spleen reactivity during incremental ascent to altitude. J Appl Physiol (1985). 2019 Jan 1;126(1):152-159. doi: 10.1152/japplphysiol.00753.2018. Epub 2018 Nov 21.
- Background: PubMed 25527774Usselman CW, Gimon TI, Nielson CA, Luchyshyn TA, Coverdale NS, Van Uum SH, Shoemaker JK. Menstrual cycle and sex effects on sympathetic responses to acute chemoreflex stress. Am J Physiol Heart Circ Physiol. 2015 Mar 15;308(6):H664-71. doi: 10.1152/ajpheart.00345.2014. Epub 2014 Dec 19.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Sean van Diepen, MD, MSc principal investigator
University of Alberta
Craig Steinback, PhD principal investigator
University of Alberta
2 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Phenylephrine Hydrochloride, Cold Pressor Test and Isocapnic Acute Hypoxia in people with Vasodilation and Vasoconstriction, run by University of Alberta at 2 sites in Canada.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 31 Oct 2022. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 2 sites in Canada. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in blood pressure (time frame: 18 minutes). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT05001048, which also lists 4 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 31 Oct 2022.