The effect of air or enriched air nitrox breathing during simulated diving on intravascular bubble formation following decompression
| ISRCTN | ISRCTN31681480 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN31681480 |
| Secondary identifying numbers | N/A |
- Submission date
- 24/02/2016
- Registration date
- 25/03/2016
- Last edited
- 25/04/2023
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Injury, Occupational Diseases, Poisoning
Plain English Summary
Background and study aims
Decompression sickness is an uncommon but serious complication of diving. It occurs when hyperbaric (high pressure) conditions during diving lead to bubbles of nitrogen forming in the blood vessels upon decompression (when the diver ascends from depth). Decompression sickness can produce many symptoms, ranging from joint pain and rashes to paralysis and death. Breathing gas mixtures with less nitrogen and higher oxygen content may decrease bubble formation after decompression. This study aims to investigate whether enriched air nitrox reduces bubble formation during simulated diving as compared to breathing normal air.
Who can participate?
Healthy volunteers aged over 18 with a diving license and without a history of a decompression accident.
What does the study involve?
Participants perform a simulated dive breathing air in the hyperbaric chamber of the CHU d’Angers. Intravascular bubble formation is assessed after the dive using cardiac (heart) ultrasound. Twelve participants prone to bubbling are then selected to perform two more simulated dives, one dive breathing air and the other dive breathing enriched air nitrox. Cardiac ultrasound is performed after each dive.
What are the possible benefits and risks of participating?
There are no benefits for the volunteers. Possible side-effects include decompression symptoms, similar to a non-simulated dive. All volunteers will be accompanied by a physician certified in hyperbaric medicine during a simulated dive.
Where is the study run from?
Centre Hospitalier Universitaire d'Angers (France)
When is the study starting and how long is it expected to run for?
January 2001 to August 2007
Who is funding the study?
Investigator initiated and funded (France)
Who is the main contact?
Prof Pierre Asfar
Contact information
Scientific
Department of Medical Intensive Care and Hyperbaric Medicine
Centre Hospitalier Universitaire d'Angers
4 rue Larrey
Angers
49933
France
Study information
| Study design | Single-center prospective double-blind study with crossover design |
|---|---|
| Primary study design | Interventional |
| Secondary study design | Randomised cross over trial |
| Study setting(s) | Hospital |
| Study type | Prevention |
| Participant information sheet | Not available in web format, please use the contact details below to request a patient information sheet |
| Scientific title | Comparison of bubble formation after diving with air or nitrox using cardiac ultrasound (Comparaison par echocardiographie Doppler du phenomene bulleux a l’issue d’une plongee a l’air et au nitrox) |
| Study acronym | NITROX |
| Study hypothesis | Enriched air nitrox reduces venous bubble scores as compared to air breathing during diving, and thereby the risk of decompression sickness in volunteers selected for high post-decompression bubble formation. |
| Ethics approval(s) | Committee for protection of human subjects in biomedical research of Pays de la Loire (Comité consultatif de protection des personnes dans la recherche biomédical des Pays de la Loire), 23/11/2001, Protocol number 2001/17 |
| Condition | Decompression illness in hyperbaric medicine |
| Intervention | The 47 divers underwent an initial simulated air dive to exclude subjects with low intravascular bubble production (Bubble score ≤ 1) in order to select divers with high bubble production (Bubble score ≥ 2). Twelve divers (10 men and two women) demonstrating high intravascular bubble production completed the study protocol in a randomized, double-blinded crossover setup. Divers were assigned to undergo one simulated dive while breathing air (Air; 21% oxygen) and one simulated dive breathing enriched air nitrox (EAN) with 36% oxygen in a randomized order. |
| Intervention type | Other |
| Primary outcome measure | Pulsed Doppler measurements of the trunk of the pulmonary artery in order to quantify intravascular bubble formation. Measurements of at least 1 minute duration were performed by a certified cardiologist, blinded for the FiO2 at 0, 30, 60 and 90 minutes after decompression. Images were recorded and analyzed for bubble scores offline. A modified bubble score was used, based on the Doppler score system of Spencer. Bubbles scores were analyzed independently by two blinded reviewers. |
| Secondary outcome measures | Decompression incidents by questionnaire 90 minutes after completion of the simulated dive. |
| Overall study start date | 01/01/2001 |
| Overall study end date | 10/08/2007 |
Eligibility
| Participant type(s) | Healthy volunteer |
|---|---|
| Age group | Adult |
| Lower age limit | 18 Years |
| Sex | Both |
| Target number of participants | 18 per group in randomized phase. No specification for number of participants for test dive was indicated in the study protocol. |
| Total final enrolment | 12 |
| Participant inclusion criteria | 1. Forty-seven human volunteers 2. Age >18 years 3. Diving experience as confirmed by possession of a French recreational diver license 4. Absence of contraindication to dive |
| Participant exclusion criteria | 1. History of decompression accident(s) 2. Oxygen administration or diving within 24 hours before simulated dive 3. Absent or low intravascular bubble production (Bubble score ≤ 1) after initial simulated test dive |
| Recruitment start date | 03/07/2002 |
| Recruitment end date | 10/08/2007 |
Locations
Countries of recruitment
- France
Study participating centre
Angers
49933
France
Sponsor information
Hospital/treatment centre
4 Rue Larrey
Angers
49000
France
| Phone | +33 (0)241 353 637 |
|---|---|
| CRC@chu-angers.fr | |
"ROR" |
https://ror.org/0250ngj72 |
Funders
Funder type
Other
No information available
Results and Publications
| Intention to publish date | 30/09/2016 |
|---|---|
| Individual participant data (IPD) Intention to share | Yes |
| IPD sharing plan summary | Available on request |
| Publication and dissemination plan | The manuscript containing the trial results has been submitted for publication |
| IPD sharing plan | The datasets generated during and/or analysed during the current study are/will be available upon request |
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Results article | results | 10/05/2016 | Yes | No | |
| Protocol (other) | 10/05/2016 | 25/04/2023 | No | No |
Editorial Notes
25/04/2023: Protocol and total final enrolment added.
11/05/2016: Publication reference added.
