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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.
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.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Sea Level Equivalent 1.2 atm abs (air) | Sham Comparator | Sham Chamber Session Sea Level Equivalent 1.2 atm abs (2.6 psig) breathing regular air 20-chamber excursion |
|
| Sea Level Equivalent 1.5 atm abs (O2) | Experimental | Hyperbaric Oxygen (1.5 atm abs) Sea Level Equivalent 1.5 atm abs (6.2 psig) breathing 100% oxygen 20-minute chamber excursion |
|
| Altitude Equivalent 1.2 atm abs (air) | Sham Comparator | Sham Chamber Session Altitude Equivalent 1.2 atm abs (5.1 psig) breathing regular air 20-minute chamber excursion |
|
| Altitude Equivalent 1.5 atm abs (O2) | Experimental | Hyperbaric Oxygen (1.5 atm abs) Altitude Equivalent 1.5 atm abs (9.6 psig) breathing 100% oxygen 20-minute chamber excursion |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Hyperbaric Oxygen (1.5 atm abs) | Drug | Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs. |
|
| 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 |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Lindell K. Weaver, MD | Intermountain Health Care, Inc. | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Intermountain Medical Center | Murray | Utah | 84107 | United States | ||
| LDS Hospital |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 19341123 | Background | Clarke D. Effective patient blinding during hyperbaric trials. Undersea Hyperb Med. 2009 Jan-Feb;36(1):13-7. | |
| 20112525 | Background | 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. |
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All participants signing informed consent continued to group assignment.
82 individuals responded to study announcements and were pre-screened by telephone, of which 25 were deemed ineligible (due to inadequate diving experience). An additional 15 individuals declined to participate (primarily due to scheduling conflicts). 42 divers and chamber inside attendants signed informed consent and participated in the study.
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| ID | Title | Description |
|---|---|---|
| FG000 | Altitude Equivalent 1.2 Atm Abs (Air) | Altitude Equivalent 1.2 atm abs (5.1 psig) breathing regular air 20-minute chamber excursion Sham Chamber Session : Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs |
| FG001 | Altitude Equivalent 1.5 Atm Abs (O2) | Altitude Equivalent 1.5 atm abs (9.6 psig) breathing 100% oxygen 20-minute chamber excursion Hyperbaric Oxygen (1.5 atm abs) : Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs. |
| FG002 | Sea Level Equivalent 1.2 Atm Abs (Air) | Sea Level Equivalent 1.2 atm abs (2.6 psig) breathing regular air 20-chamber excursion Sham Chamber Session : Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs |
| FG003 | Sea Level Equivalent 1.5 Atm Abs (O2) | Sea Level Equivalent 1.5 atm abs (6.2 psig) breathing 100% oxygen 20-minute chamber excursion Hyperbaric Oxygen (1.5 atm abs) : Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs. |
| Title | Milestones | Reasons Not Completed | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Overall Study |
|
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| ID | Title | Description |
|---|---|---|
| BG000 | Altitude Equivalent 1.2 Atm Abs (Air) | Altitude Equivalent 1.2 atm abs (5.1 psig) breathing regular air 20-minute chamber excursion Sham Chamber Session : Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs |
| BG001 | Altitude Equivalent 1.5 Atm Abs (O2) |
| Units | Counts |
|---|---|
| Participants |
|
| Title | Description | Population Description | Parameter Type | Dispersion Type | Unit of Measure | Calculate Percentage | Denominator Units Selected | Denominators | Classes |
|---|---|---|---|---|---|---|---|---|---|
| Age, Categorical | Count of Participants |
| Type | Title | Description | Population Description | Reporting Status | Anticipated Posting Date | Parameter Type | Dispersion Type | Unit of Measure | Calculate Percentage | Time Frame | Units Analyzed | Denominator Units Selected | Arm/Group Information | Denominators | Classes | Analyses | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Primary | 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. | All participants who enrolled in the study were analyzed. | Posted | Number | participants | Within 15 minutes of chamber excursion |
|
Adverse events were collected from the time that participants signed consent until they departed after the chamber excursion (approximately 1 hour).
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| ID | Title | Description | Deaths (Affected) | Deaths (At Risk) | Serious Events (Affected) | Serious Events (At Risk) | Other Events (Affected) | Other Events (At Risk) |
|---|---|---|---|---|---|---|---|---|
| EG000 | Altitude Equivalent 1.2 Atm Abs (Air) | Altitude Equivalent 1.2 atm abs (5.1 psig) breathing regular air 20-minute chamber excursion Sham Chamber Session : Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs |
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| Term | Organ System | Source Vocabulary | Assessment Type | Notes | Statistical Information |
|---|---|---|---|---|---|
| Headache | Nervous system disorders | Non-systematic Assessment | One participant complained of a slight headache following the chamber excursion, which he attributed to voluntarily skipping meals that day. |
Smaller sample size; enrollment was stopped at 42 participants when investigators had exhausted the planned recruitment methods. Very few inside attendants enrolled. Pressures in this study were relatively close.
| Title | Organization | Phone | Extension | |
|---|---|---|---|---|
| Lindell K. Weaver, MD | Intermountain Healthcare | 801-408-3623 | lindell.weaver@imail.org |
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| ID | Term |
|---|---|
| D000070642 | Brain Injuries, Traumatic |
| ID | Term |
|---|---|
| D001930 | Brain Injuries |
| D001927 | Brain Diseases |
| D002493 | Central Nervous System Diseases |
| D009422 | Nervous System Diseases |
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|
| Sham Chamber Session | Drug | Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs |
|
|
| Salt Lake City |
| Utah |
| 84143 |
| United States |
| Background | 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. |
| 22908836 | Result | 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. |
Altitude Equivalent 1.5 atm abs (9.6 psig) breathing 100% oxygen 20-minute chamber excursion Hyperbaric Oxygen (1.5 atm abs) : Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs. |
| BG002 | Sea Level Equivalent 1.2 Atm Abs (Air) | Sea Level Equivalent 1.2 atm abs (2.6 psig) breathing regular air 20-chamber excursion Sham Chamber Session : Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs |
| BG003 | Sea Level Equivalent 1.5 Atm Abs (O2) | Sea Level Equivalent 1.5 atm abs (6.2 psig) breathing 100% oxygen 20-minute chamber excursion Hyperbaric Oxygen (1.5 atm abs) : Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs. |
| BG004 | Total | Total of all reporting groups |
| Participants |
|
| Age Continuous | Mean | Standard Deviation | years |
|
| Sex: Female, Male | Count of Participants | Participants |
|
| Region of Enrollment | Number | participants |
|
| OG002 | Sea Level Equivalent 1.2 Atm Abs (Air) | Sea Level Equivalent 1.2 atm abs (2.6 psig) breathing regular air 20-chamber excursion Sham Chamber Session : Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs |
| OG003 | Sea Level Equivalent 1.5 Atm Abs (O2) | Sea Level Equivalent 1.5 atm abs (6.2 psig) breathing 100% oxygen 20-minute chamber excursion Hyperbaric Oxygen (1.5 atm abs) : Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs. |
|
|
| Primary | Participant Perception of Depth | Mean depth perception for participants providing a free response. | 23 of 42 participants provided a numerical response. The remainder selected "I do not know." | Posted | Mean | Standard Deviation | fsw | Within 15 minutes of chamber excursion |
|
|
|
| Primary | Participant Perception of Breathing Gas | Percent of participants in each arm guessing that their breathing gas was 100% oxygen. | 40 of 42 participants provided an answer to this question. | Posted | Number | percentage of participants | Within 15 minutes of chamber excursion |
|
|
|
| 0 |
| 10 |
| 1 |
| 10 |
| EG001 | Altitude Equivalent 1.5 Atm Abs (O2) | Altitude Equivalent 1.5 atm abs (9.6 psig) breathing 100% oxygen 20-minute chamber excursion Hyperbaric Oxygen (1.5 atm abs) : Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs. | 0 | 12 | 0 | 12 |
| EG002 | Sea Level Equivalent 1.2 Atm Abs (Air) | Sea Level Equivalent 1.2 atm abs (2.6 psig) breathing regular air 20-chamber excursion Sham Chamber Session : Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs | 0 | 8 | 0 | 8 |
| EG003 | Sea Level Equivalent 1.5 Atm Abs (O2) | Sea Level Equivalent 1.5 atm abs (6.2 psig) breathing 100% oxygen 20-minute chamber excursion Hyperbaric Oxygen (1.5 atm abs) : Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs. | 0 | 12 | 0 | 12 |
|
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| D006259 |
| Craniocerebral Trauma |
| D020196 | Trauma, Nervous System |
| D014947 | Wounds and Injuries |