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Effects of Mild Hypobaric Hypoxia on Oxygen Saturation During Sleep

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT00659009
Recruitment Status : Completed
First Posted : April 16, 2008
Last Update Posted : August 15, 2012
Simon Fraser University
Massey University
Information provided by (Responsible Party):
The Boeing Company

Brief Summary:
Ascent to altitude lowers oxygen saturation. In addition, sleep lowers oxygen saturation at any altitude. In a prior study, we observed that sleep at 8000 feet resulted in pronounced reduction in oxygen saturation, but did not result in reduced post sleep neurobehavioral performance or impaired sleep quality or quantity. We plan to do a more sophisticated physiological evaluation of the respiratory mechanisms responsible for the reduced oxygen saturation and determine if there are any adverse consequences to this level of intermittent hypoxia. We anticipate that central respiratory apnea is the physiologic mechanism, and that there will not be persistent changes in autonomic nervous activity measured by heart rate variability.

Condition or disease Intervention/treatment Phase
Sleep-related Respiratory Disturbance Other: Reduced barometric pressure Other: Sea level equivalent barometric pressure Not Applicable

Detailed Description:

This study has 6 primary objectives/hypotheses:

  1. Replicate findings of earlier study in which no effects of altitude were observed on post sleep neurobehavioral performance, sleep quantity or quality.
  2. Determine if sleep at 6000 feet has effects similar to sleep at 8000 feet.
  3. Identify if central or obstructive apnea is responsible for the reduction in oxygen saturation observed during sleep at 8000 feet.
  4. Determine if respiratory abnormalities observed at 6000 feet are similar but less severe than at 8000 feet.
  5. Determine if there are individual differences in respiratory physiology at sea level that enable prediction of pronounced respiratory disturbances during sleep at altitude.
  6. Determine if changes in autonomic nervous activity, measured by heart rate variability, occur, and if so, do they persist for 8 hours.

Twenty healthy males between 30 and 60 years of age whose baseline apnea-hypopnea index is less than 15/hour will be recruited from the general population surrounding Burnaby, British Columbia, Canada. Women are excluded because of the changes in sleep structure associated with the menstrual cycle.

Participants will be involved in the blinded crossover study for a 14 day period during which time they will monitor their sleep by actigraphy and sleep diaries, will spend 2 nights an altitude chamber at Simon Fraser University at ambient barometric pressure to become adapted to sleeping in that environment, then spend 3 study nights, each followed by 2 rest nights, sleeping at barometric pressures equivalent to sea level, 6000 feet, and 8000 feet. The order of exposures will be randomly balanced.

Pre study physiologic measures will include hypoxic ventilatory response, hypercapnic ventilatory response, and during one of the adaptation nights, apnea hypoxia index. Study sessions will consist of a 4 hour presleep period, a 6 hour sleep period, and a 1 hour post sleep period at the study barometric pressure. During the study sessions, heart rate, SpO2, polysomnographic measures, nasal air flow rates, and chest motion will be monitored and recorded. Psychomotor Vigilance Task response time will be measured before and after the sleep period. Heart rate will be recorded by ambulatory recording equipment for 8 hours following return to ambient barometric pressure conditions. This will be analyzed to determine if changes in heart rate variability are persistent.

Outcomes of primary interest will include total sleep time, duration of sleep stages, oxygen saturation, heart rate and heart rate variability, respiratory rates, air flow, and chest motion to assess if central or obstructive apnea is temporally related to reductions in oxygen saturation.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 16 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary Purpose: Basic Science
Official Title: The Effects of Mild Hypobaric Hypoxia on Oxygen Saturation During Sleep: An Investigation of the Physiologic Mechanisms and Significance
Study Start Date : May 2008
Actual Primary Completion Date : March 2009
Actual Study Completion Date : March 2009

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Oxygen Therapy

Arm Intervention/treatment
Active Comparator: 1
Barometric pressure equivalent to sea level (760 mm Hg).
Other: Sea level equivalent barometric pressure
Sleep in barometric pressure equivalent to sea level.

Experimental: 2
Barometric pressure equivalent to 6000 feet (609 mm Hg)
Other: Reduced barometric pressure
Sleep in reduced barometric pressure environment.

Experimental: 3
Barometric pressure equivalent to 8000 feet (565 mm Hg).
Other: Reduced barometric pressure
Sleep in reduced barometric pressure environment.

Primary Outcome Measures :
  1. SpO2 [ Time Frame: Continuous during sleep ]
  2. Respiratory Disturbance [ Time Frame: Continuous during sleep ]
  3. Sleep architecture [ Time Frame: Continuous during sleep ]

Secondary Outcome Measures :
  1. Heart rate variability [ Time Frame: Continuous during sleep and 8 hr following exposure ]

Information from the National Library of Medicine

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Ages Eligible for Study:   30 Years to 60 Years   (Adult)
Sexes Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Male
  • Between 30 and 60 years of age.
  • Healthy, able to pass FAA Class III examination
  • Body mass index less than 30
  • Height less than 75 inches
  • Ability to read and speak English

Exclusion Criteria:

  • Prolonged residence above 5000 feet
  • Recent travel to altitudes above 5000 feet
  • Use of drugs or medications that affect sleep
  • History of mood or psychiatric disorders that affect sleep.
  • History of medical conditions that increase risk of adverse effects of hypoxia.
  • Apnea hypopnea index greater than 15/hr at ground level.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT00659009

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Canada, British Columbia
Environmental Physiology Unit, School of Kinesiology, Simon Fraser University
Burnaby, British Columbia, Canada, V5A 1S6
Sponsors and Collaborators
The Boeing Company
Simon Fraser University
Massey University
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Principal Investigator: James M Muhm, MD, MPH The Boeing Company

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Responsible Party: The Boeing Company Identifier: NCT00659009     History of Changes
Other Study ID Numbers: Boeing-003
First Posted: April 16, 2008    Key Record Dates
Last Update Posted: August 15, 2012
Last Verified: February 2010
Keywords provided by The Boeing Company:
hypobaric hypoxia
neurobehavioral performance
Effect of altitude on sleep-related respiratory disturbance
Additional relevant MeSH terms:
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Signs and Symptoms, Respiratory
Signs and Symptoms