The Response of Intraocular Pressure to Systemic Hypercapnia and Hyperoxia

The recruitment status of this study is unknown because the information has not been verified recently.
Verified November 2010 by University of Toronto.
Recruitment status was  Not yet recruiting
Sponsor:
Collaborators:
University Health Network, Toronto
Thornhill Research
Information provided by:
University of Toronto
ClinicalTrials.gov Identifier:
NCT01325285
First received: February 15, 2011
Last updated: August 17, 2011
Last verified: November 2010
  Purpose

The purpose of this study is to determine how intraocular pressure responds to changes in the levels of carbon dioxide or oxygen that a healthy individual inspires.


Condition Intervention
Intraocular Pressure
Device: RespirAct

Study Type: Observational
Study Design: Observational Model: Case-Only
Time Perspective: Cross-Sectional
Official Title: The Response of Intraocular Pressure to Systemic Hypercapnia and Hyperoxia

Further study details as provided by University of Toronto:

Primary Outcome Measures:
  • Intraocular pressure [ Time Frame: Intraocular pressure will be measured during the study visit, ten minutes into each of the seven inhaled gas provocation stages ] [ Designated as safety issue: No ]
    Intraocular pressure will be measured using Goldmann applanation tonometry.


Secondary Outcome Measures:
  • Retinal blood flow [ Time Frame: Retinal blood flow will be measured during the second (optional) study visit, ten minutes into each of the seven inhaled gas provocation stages ] [ Designated as safety issue: No ]
    Retinal blood flow will be measured using the Canon Laser Blood Flowmeter in a subset of participants asked to return for a second visit. This will demonstrate that retinal blood flow behaves as the study claims that it does.


Estimated Enrollment: 14
Study Start Date: August 2011
Estimated Study Completion Date: September 2011
Estimated Primary Completion Date: September 2011 (Final data collection date for primary outcome measure)
Intervention Details:
    Device: RespirAct

    Participants will breathe through a mask connected to a sequential rebreathing circuit and gas blender. The following seven gas stages will be targeted for about 10 minutes each:

    1. Baseline, measured in eye A (PETCO2=38mmHg and PETO2=100mmHg)
    2. 10% hypercapnic increase, measured in eye A (PETCO2=42mmHg and PETO2=100mmHg)
    3. 20% hypercapnic increase, measured in eye A (PETCO2=46mmHg and PETO2=100mmHg)
    4. Baseline, measured in both eyes (PETCO2=38mmHg and PETO2=100mmHg)
    5. 250% hyperoxic increase, measured in eye B (PETCO2=38mmHg and PETO2=250mmHg)
    6. 500% hyperoxic increase, measured in eye B (PETCO2=38mmHg and PETO2=500mmHg)
    7. Baseline, measured in eye B (PETCO2=38mmHg and PETO2=100mmHg)
    Other Name: Inhaled gas provocations
Detailed Description:

In response to changes in the composition of inhaled gases, blood vessels will dilate or constrict. As a result, hypercapnia or hyperoxia may affect the production and drainage of aqueous humour in the anterior chamber of the eye. The balance between the production and drainage of the aqueous humour determines the intraocular pressure. As this system is hydrodynamic, it is expected that any increase or decrease in the production of aqueous humour due to dilation or constriction of the capillaries within the ciliary body will be compensated by increased or decreased drainage at the trabecular meshwork. Therefore intraocular pressure is not expected to show a response to hypercapnia or hyperoxia, but this supposition needs to be tested in a stably controlled manner of inducing inhaled gas provocations. This study will measure the intraocular pressure at varying levels of hypercapnia and hyperoxia using a sequential rebreathing circuit and automated gas blender. This will allow the precise targeting and stable control of end-tidal partial pressure values of carbon dioxide and oxygen.

In this study, intraocular pressure will be measured at seven different inhaled gas stages. The seven stages are as follows:

  1. Baseline, measured in eye A (PETCO2=38mmHg and PETO2=100mmHg)
  2. 10% hypercapnic increase, measured in eye A (PETCO2=42mmHg and PETO2=100mmHg)
  3. 20% hypercapnic increase, measured in eye A (PETCO2=46mmHg and PETO2=100mmHg)
  4. Baseline, measured in both eyes (PETCO2=38mmHg and PETO2=100mmHg)
  5. 250% hyperoxic increase, measured in eye B (PETCO2=38mmHg and PETO2=250mmHg)
  6. 500% hyperoxic increase, measured in eye B (PETCO2=38mmHg and PETO2=500mmHg)
  7. Baseline, measured in eye B (PETCO2=38mmHg and PETO2=100mmHg)
  Eligibility

Ages Eligible for Study:   18 Years to 30 Years
Genders Eligible for Study:   Both
Accepts Healthy Volunteers:   Yes
Sampling Method:   Non-Probability Sample
Study Population

Healthy young individuals (age 18-30)

Criteria

Inclusion Criteria:

  • Age range 18-30 years old
  • Visual acuity of 20/20 or better

Exclusion Criteria:

  • Refractive error >±6.00 DS and/or ± 2.00 DC
  • History or presence of ocular disease
  • Family history of diabetes or glaucoma
  • History of intraocular or refractive surgery
  • Nursing or pregnant women
  • History of clinically diagnosed endocrine disease
  • History of vascular disease, cardiovascular disease, or any treated respiratory disorders (seasonal asthma excluded from this so long as subject not taking Rx at the time)
  • History of systemic hypertension
  • Habitual smoking
  • Use of medications that affect blood flow
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT01325285

Contacts
Contact: Alanna Adleman, BSc 416-603-5694 aadleman@uhnresearch.ca
Contact: Tien Wong, BSc 416-603-5694 twong@uhnresearch.ca

Locations
Canada, Ontario
Toronto Western Hospital Not yet recruiting
Toronto, Ontario, Canada
Contact: Alanna Adleman, BSc    416-603-5694    aadleman@uhnresearch.ca   
Contact: Tien Wong, BSc    416-603-5694    twong@uhnresearch.ca   
Principal Investigator: Christopher Hudson, PhD         
Sub-Investigator: Joseph Fisher, FRCPC, MD         
Sub-Investigator: Richard Cheng, BSc         
Sponsors and Collaborators
University of Toronto
University Health Network, Toronto
Thornhill Research
Investigators
Principal Investigator: Christopher Hudson, PhD University of Toronto
  More Information

Publications:
Responsible Party: Dr. Christopher Hudson, University of Toronto, University of Waterloo, and Toronto Western Research Institute
ClinicalTrials.gov Identifier: NCT01325285     History of Changes
Other Study ID Numbers: 10-0655
Study First Received: February 15, 2011
Last Updated: August 17, 2011
Health Authority: Canada: Health Canada

Keywords provided by University of Toronto:
Intraocular pressure
Hypercapnia
Hyperoxia
Rebreathing circuit

Additional relevant MeSH terms:
Hypercapnia
Hyperoxia
Signs and Symptoms, Respiratory
Signs and Symptoms

ClinicalTrials.gov processed this record on August 28, 2014