Test of Chamber Pressure to Divers and Chamber Attendants (TOP-DIVER)

Test of Chamber Pressure to Divers and Chamber Attendants: A Blinded Trial to Investigate if "Pressure-familiar" Individuals Can Determine Pressure

SCUBA divers and chamber inside attendants will undergo a brief hyperbaric chamber excursion and will be asked to what chamber pressure they were compressed and what gas they breathed.

Study Overview

• Status: Completed
• Conditions: Traumatic Brain Injury
• Intervention / Treatment: Drug: Sham Chamber Session; Drug: Hyperbaric Oxygen (1.5 atm abs)

Detailed Description

In clinical trials evaluating hyperbaric oxygen, blinding can be challenging. Options for participant blinding include offering regular air at a lower pressure than the hyperbaric oxygen intervention, or compressing all participants to the same pressure but providing different gas mixes to the active and sham arms.

In some trials of hyperbaric oxygen for brain injury, investigators offer a sham chamber session (regular air at 1.2 atmospheres absolute [atm abs]) compared to the active intervention, hyperbaric oxygen (100% oxygen at 1.5 atm abs). It is unknown whether individuals familiar with pressure changes, such as divers and hyperbaric chamber inside attendants, could discern the difference between these pressures and thereby become unblinded to study allocation.

In this study, 80 experienced divers and chamber inside attendants will be enrolled and randomly assigned to one of four possible chamber pressures and one of two breathing gases. After a brief hyperbaric chamber excursion, they will be asked to what chamber pressure they were compressed and what gas they breathed. If participants can accurately report chamber pressure or breathing gas, pressure-familiar individuals should be excluded from blinded clinical trials of hyperbaric oxygen.

• Study Type: Interventional
• Enrollment (Actual): 42
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Utah
    • Murray, Utah, United States, 84107
      • Intermountain Medical Center
    • Salt Lake City, Utah, United States, 84143
      • LDS Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Adult, age 18 - 65 years
• Completion of medical history questionnaire without concerns identified for exposure to increased pressure
• Familiarity with atmospheric pressure change:
• Experienced and active hyperbaric chamber inside attendant: more than 50 hyperbaric compressions, with more than 4 have been in the last 4 months; or
• Experienced and active SCUBA diver: more than 20 lifetime compressed gas open water (not swimming pool) dives, with more than 10 in the last 12 months
• Able to equalize middle ear pressure easily

Exclusion Criteria:

• Pregnancy
• Known risk for barotrauma, as identified on the medical history questionnaire, such as:
• Recent (within 12 months) inner ear or sinus surgery
• Spontaneous pneumothorax
• Pulmonary cysts
• Emphysema
• Bullous lung disease
• Chronic obstructive pulmonary disease needing chronic active therapy
• Inability to tolerate chamber confinement or pressure
• Presence of heart failure
• Presence of any implanted electrical device, except hyperbaric-approved pacemakers
• Presence of middle-ear tympanostomy tubes

Study Plan

How is the study designed?

Design Details

• Allocation: Randomized
• Interventional Model: Single Group Assignment
• Masking: Triple

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Sham Comparator: Sea Level Equivalent 1.2 atm abs (air); Sham Chamber Session Sea Level Equivalent 1.2 atm abs (2.6 psig) breathing regular air 20-chamber excursion	Drug: Sham Chamber Session; Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs; Other Names: Sham control; Air pressurization
Experimental: Sea Level Equivalent 1.5 atm abs (O2); Hyperbaric Oxygen (1.5 atm abs) Sea Level Equivalent 1.5 atm abs (6.2 psig) breathing 100% oxygen 20-minute chamber excursion	Drug: Hyperbaric Oxygen (1.5 atm abs); Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs.; Other Names: HBOT; HBO; HBO2
Sham Comparator: Altitude Equivalent 1.2 atm abs (air); Sham Chamber Session Altitude Equivalent 1.2 atm abs (5.1 psig) breathing regular air 20-minute chamber excursion	Drug: Sham Chamber Session; Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs; Other Names: Sham control; Air pressurization
Experimental: Altitude Equivalent 1.5 atm abs (O2); Hyperbaric Oxygen (1.5 atm abs) Altitude Equivalent 1.5 atm abs (9.6 psig) breathing 100% oxygen 20-minute chamber excursion	Drug: Hyperbaric Oxygen (1.5 atm abs); Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs.; Other Names: HBOT; HBO; HBO2

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Participants Indicating "I do Not Know" on Depth Questionnaire.	Participants indicating "I do not know" on depth questionnaire instead of providing a free response guess.	Within 15 minutes of chamber excursion
Participant Perception of Depth	Mean depth perception for participants providing a free response.	Within 15 minutes of chamber excursion
Participant Perception of Breathing Gas	Percent of participants in each arm guessing that their breathing gas was 100% oxygen.	Within 15 minutes of chamber excursion

Collaborators and Investigators

• Sponsor: Intermountain Health Care, Inc.

Publications and helpful links

General Publications

• Clarke D. Effective patient blinding during hyperbaric trials. Undersea Hyperb Med. 2009 Jan-Feb;36(1):13-7.
• Jansen T, Mortensen CR, Tvede MF. It is possible to perform a double-blind hyperbaric session: a double-blinded randomized trial performed on healthy volunteers. Undersea Hyperb Med. 2009 Sep-Oct;36(5):347-51.
• Weaver LK, Hopkins RO, Churchill S, Haberstock D. Double-Blinding is Possible in Hyperbaric Oxygen (HBO2) Randomized Clinical Trials (RCT) Using a Minimal Chamber Pressurization as Control. Undersea Hyperb Med 1997;24(Suppl):36.
• Weaver LK, Churchill SK, Bell J, Deru K, Snow GL. A blinded trial to investigate whether 'pressure-familiar' individuals can determine chamber pressure. Undersea Hyperb Med. 2012 Jul-Aug;39(4):801-5.

Study record dates

Study Major Dates

• Study Start: July 1, 2011
• Primary Completion (Actual): October 1, 2011
• Study Completion (Actual): October 1, 2011

Study Registration Dates

• First Submitted: September 2, 2011
• First Submitted That Met QC Criteria: September 7, 2011
• First Posted (Estimate): September 8, 2011

Study Record Updates

• Last Update Posted (Estimate): February 15, 2013
• Last Update Submitted That Met QC Criteria: February 12, 2013
• Last Verified: December 1, 2012

More Information

Terms related to this study

• Keywords: Hyperbaric oxygen
• Additional Relevant MeSH Terms: Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Wounds and Injuries; Craniocerebral Trauma; Trauma, Nervous System; Brain Injuries; Brain Injuries, Traumatic
• Other Study ID Numbers: 1023955