Effect of Nitrous Oxide (N2O) on Intraocular Pressure in Healthy Volunteers
Condition: Glaucoma; Sedation
MeSH terms: Glaucoma
Intervention: Nitrous oxide
Intervention description: Nitrous oxide sedation by inhalation
Intervention MeSH terms: Nitrous Oxide
Phase: Phase 4
Study type: Interventional
Primary purpose: Diagnostic
Intervention model: Single Group Assignment
Masking: Single (Investigator)
Enrollment: 20.0
Sex: All
Minimum age: 18 Years
Maximum age: 40 Years
Healthy volunteers: Accepts Healthy Volunteers
Keywords: Glaucoma; Nitrous oxide

Summary:

      The purpose of this study is to learn if breathing nitrous oxide (also known as "laughing
      gas") changes the pressure in a person's eyes. Some patients who need regular eye exams to
      measure their eye pressure often need to be put to sleep with medicine in order to complete
      the eye exam. Some of these medicines are known to cause changes in a person's eye pressure.
      Because of this, such medicines are avoided if the eye doctor needs to measure the patient's
      eye pressure. One medicine that is frequently used to put patients to sleep is nitrous oxide.
      No one really knows what effect nitrous oxide might have on a persons' eye pressure. The
      investigators are interested to see if nitrous oxide causes an increase, decrease, or no
      change in eye pressure. The investigators also want to investigate if there is a difference
      in the effects of nitrous oxide on eye pressure between males and females. Understanding
      these effects of nitrous oxide is important because during such eye exams, the eye doctor
      uses the pressure measurements to make important decisions about treatment and surgery
      options for the patient.

      The investigators hypothesize that the use of inhaled nitrous oxide (N2O) will result in a
      decrease in IOP in healthy volunteers.

      The investigators aim to determine the magnitude and duration of change, if any, in IOP
      caused by inhalation of N2O, and to assess if the gender of the patient has a role in this
      effect.
    

Eligibility criteria:

        Inclusion Criteria:

          -  Adults aged 18-40

          -  American Society of Anesthesiologists Physical Classification System (ASA) Status 1-2

          -  Nil per os (NPO) prior to study (2 hrs clear liquids, 4 hrs milk, 6 hrs light food, 8
             hrs heavy/greasy food)

        Exclusion Criteria:

          -  Lack of volunteer consent

          -  Pregnancy

          -  History of features suggestive of a difficult airway on pre-anesthetic evaluation and
             physical examination

          -  Active gastroesophageal reflux disease

          -  Active obstructive sleep apnea

          -  History of recent trauma

          -  History of pneumothorax or lung cyst

          -  History of Vitamin B12 deficiency

          -  History of recent middle ear surgery (<3months)

          -  Current or recent (<3 weeks) respiratory tract infection

          -  Any acute illness or exacerbation of chronic illness such as asthma, chronic lung
             disease etc.

          -  Any history of cardiac ischemia (angina), myocardial infarction, or cardiac
             dysrhythmia.

          -  Myopia greater than -3 spherical equivalents or hyperopia greater than +3 spherical
             equivalents

          -  History of eye surgery of any sort, including refractive surgery, cataracts, and
             vitrectomy

          -  History of any ocular disease or infection