The Response of Intraocular Pressure to Systemic Hypercapnia and Hyperoxia

Intraocular Pressure Clinical Trial

Official title:

The Response of Intraocular Pressure to Systemic Hypercapnia and Hyperoxia

Clinical Trial Details — Status: Not yet recruiting

Administrative data

• NCT number: NCT01325285
• Other study ID #: 10-0655
• Status: Not yet recruiting
• Phase: N/A
• First received: February 15, 2011
• Last updated: August 17, 2011
• Start date: August 2011
• Est. completion date: September 2011

Study information

• Verified date: November 2010
• Source: University of Toronto
• Contact: Alanna Adleman, BSc
• Phone: 416-603-5694
• Email: aadleman[@]uhnresearch.ca
• Is FDA regulated: No
• Health authority: Canada: Health Canada
• Study type: Observational

Clinical Trial Summary

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.

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)

Recruitment information / eligibility

• Status: Not yet recruiting
• Enrollment: 14
• Est. completion date: September 2011
• Est. primary completion date: September 2011
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Both
• Age group: 18 Years to 30 Years

Eligibility

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

Study Design

Observational Model: Case-Only, Time Perspective: Cross-Sectional

Related Conditions & MeSH terms

• Hypercapnia
• Hyperoxia
• Intraocular Pressure

Intervention

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: Baseline, measured in eye A (PETCO2=38mmHg and PETO2=100mmHg) 10% hypercapnic increase, measured in eye A (PETCO2=42mmHg and PETO2=100mmHg) 20% hypercapnic increase, measured in eye A (PETCO2=46mmHg and PETO2=100mmHg) Baseline, measured in both eyes (PETCO2=38mmHg and PETO2=100mmHg) 250% hyperoxic increase, measured in eye B (PETCO2=38mmHg and PETO2=250mmHg) 500% hyperoxic increase, measured in eye B (PETCO2=38mmHg and PETO2=500mmHg) Baseline, measured in eye B (PETCO2=38mmHg and PETO2=100mmHg)

Locations

Country	Name	City	State
Canada	Toronto Western Hospital	Toronto	Ontario

Sponsors (3)

Lead Sponsor	Collaborator
University of Toronto	Thornhill Research, University Health Network, Toronto

Country where clinical trial is conducted

Canada, 

References & Publications (2)

Hosking SL, Harris A, Chung HS, Jonescu-Cuypers CP, Kagemann L, Roff Hilton EJ, Garzozi H. Ocular haemodynamic responses to induced hypercapnia and hyperoxia in glaucoma. Br J Ophthalmol. 2004 Mar;88(3):406-11. — View Citation

Slessarev M, Han J, Mardimae A, Prisman E, Preiss D, Volgyesi G, Ansel C, Duffin J, Fisher JA. Prospective targeting and control of end-tidal CO2 and O2 concentrations. J Physiol. 2007 Jun 15;581(Pt 3):1207-19. Epub 2007 Apr 19. — View Citation

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Intraocular pressure	Intraocular pressure will be measured using Goldmann applanation tonometry.	Intraocular pressure will be measured during the study visit, ten minutes into each of the seven inhaled gas provocation stages	No
Secondary	Retinal blood flow	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.	Retinal blood flow will be measured during the second (optional) study visit, ten minutes into each of the seven inhaled gas provocation stages	No