Traumatic Brain Injury
Conditions
Keywords
Hyperbaric oxygen
Brief summary
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.
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.
Interventions
DRUGHyperbaric Oxygen (1.5 atm abs)
Hyperbaric oxygen (100% oxygen) delivered at a chamber pressure of 1.5 atm abs.
DRUGSham Chamber Session
Sham control chamber session: regular air delivered at a chamber pressure of 1.2 atm abs
Sponsors
Intermountain Health Care, Inc.
Study design
Allocation
RANDOMIZED
Intervention model
SINGLE_GROUP
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Participants Indicating I do Not Know on Depth Questionnaire. | Within 15 minutes of chamber excursion | Participants indicating I do not know on depth questionnaire instead of providing a free response guess. |
| Participant Perception of Depth | Within 15 minutes of chamber excursion | Mean depth perception for participants providing a free response. |
| Participant Perception of Breathing Gas | Within 15 minutes of chamber excursion | Percent of participants in each arm guessing that their breathing gas was 100% oxygen. |
Countries
United States
Participant flow
Recruitment details
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.
Pre-assignment details
All participants signing informed consent continued to group assignment.
Participants by arm
| Arm | Count |
|---|---|
| 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 | 10 |
| 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. | 12 |
| 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 | 8 |
| 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. | 12 |
| Total | 42 |
Baseline characteristics
| Characteristic | Sea Level Equivalent 1.2 Atm Abs (Air) | Sea Level Equivalent 1.5 Atm Abs (O2) | Total | Altitude Equivalent 1.2 Atm Abs (Air) | Altitude Equivalent 1.5 Atm Abs (O2) |
|---|---|---|---|---|---|
| Age, Categorical <=18 years | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical >=65 years | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical Between 18 and 65 years | 8 Participants | 12 Participants | 42 Participants | 10 Participants | 12 Participants |
| Age Continuous | 47 years STANDARD_DEVIATION 9.3 | 45 years STANDARD_DEVIATION 13 | 46 years STANDARD_DEVIATION 10 | 45 years STANDARD_DEVIATION 10 | 49 years STANDARD_DEVIATION 7.8 |
| Region of Enrollment United States | 8 participants | 12 participants | 42 participants | 10 participants | 12 participants |
| Sex: Female, Male Female | 1 Participants | 4 Participants | 10 Participants | 3 Participants | 2 Participants |
| Sex: Female, Male Male | 7 Participants | 8 Participants | 32 Participants | 7 Participants | 10 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk | EG003 affected / at risk |
|---|---|---|---|---|
| deaths Total, all-cause mortality | — / — | — / — | — / — | — / — |
| other Total, other adverse events | 1 / 10 | 0 / 12 | 0 / 8 | 0 / 12 |
| serious Total, serious adverse events | 0 / 10 | 0 / 12 | 0 / 8 | 0 / 12 |
Outcome results
Primary
Participant Perception of Breathing Gas
Percent of participants in each arm guessing that their breathing gas was 100% oxygen.
Time frame: Within 15 minutes of chamber excursion
Population: 40 of 42 participants provided an answer to this question.
| Arm | Measure | Value (NUMBER) |
|---|---|---|
| Altitude Equivalent 1.2 Atm Abs (Air) | Participant Perception of Breathing Gas | 80 percentage of participants |
| Altitude Equivalent 1.5 Atm Abs (O2) | Participant Perception of Breathing Gas | 91 percentage of participants |
| Sea Level Equivalent 1.2 Atm Abs (Air) | Participant Perception of Breathing Gas | 88 percentage of participants |
| Sea Level Equivalent 1.5 Atm Abs (O2) | Participant Perception of Breathing Gas | 67 percentage of participants |
Primary
Participant Perception of Depth
Mean depth perception for participants providing a free response.
Time frame: Within 15 minutes of chamber excursion
Population: 23 of 42 participants provided a numerical response. The remainder selected I do not know.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Altitude Equivalent 1.2 Atm Abs (Air) | Participant Perception of Depth | 65 fsw | Standard Deviation 13 |
| Altitude Equivalent 1.5 Atm Abs (O2) | Participant Perception of Depth | 35 fsw | Standard Deviation 16 |
| Sea Level Equivalent 1.2 Atm Abs (Air) | Participant Perception of Depth | 23 fsw | Standard Deviation 12 |
| Sea Level Equivalent 1.5 Atm Abs (O2) | Participant Perception of Depth | 23 fsw | Standard Deviation 14 |
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.
Time frame: Within 15 minutes of chamber excursion
Population: All participants who enrolled in the study were analyzed.
| Arm | Measure | Value (NUMBER) |
|---|---|---|
| Altitude Equivalent 1.2 Atm Abs (Air) | Participants Indicating I do Not Know on Depth Questionnaire. | 7 participants |
| Altitude Equivalent 1.5 Atm Abs (O2) | Participants Indicating I do Not Know on Depth Questionnaire. | 4 participants |
| Sea Level Equivalent 1.2 Atm Abs (Air) | Participants Indicating I do Not Know on Depth Questionnaire. | 4 participants |
| Sea Level Equivalent 1.5 Atm Abs (O2) | Participants Indicating I do Not Know on Depth Questionnaire. | 4 participants |