Reduction of Venous Emboli Load After Breathing Normobaric Oxygen Compared to Air

Mängden kvävgasbubblor i Blodet Efter Dykning Vid Syrgasandning jämfört Med Luftandning

Primary objective:

- Assessment of venous gas emboli load post diving when breathing normobaric oxygen compared to air.

Secondary objective:

• Assessment of fluid markers of central nervous system injury in blood post diving
• Assessment of fluid markers of inflammation and endothelial dysfunction in blood post diving

Tertiary objective:

- Assessment of DCS frequency

Study Overview

• Status: Completed
• Conditions: Inflammation; Endothelial Dysfunction; Decompression Sickness; Diving Medicine; Hyperbaric; Central Nervous Injury
• Intervention / Treatment: Drug: Oxygen; Other: Air

Detailed Description

This is a prospective, double blinded, randomized, cross-over study in Sweden. The study was performed in two different sets, each containing standardized dives in a wet hyperbaric chamber. The dives included movement on depth.

In each study set 16-32 professional divers performed no-decompression dives to a depth of 42 metres of seawater (msw). The gas used during the dives was compressed air.

After surfacing the divers breathed either normobaric oxygen or normobaric air on a demand mask. Timing of oxygen/air-breathing differed between study sets. The content of breathing gas was unknown to both divers and examining personnel.

Immediately post dive the divers were assessed using either transthoracic doppler ultrasound (TTD) or transthoracic 2-D ultrasound (TTE) to determine VGE load, time to VGE detection and VGE duration.

Signs of DCS were actively sought.

TTD measurements were done every five minutes during the first 30 minutes, thereafter every 15 minutes during 90 minutes.

TTE was performed every 30 minutes, using an apical 4-chamber view.

Blood samples were obtained pre-dive, 30-45 minutes post-dive and 120 minutes post-dive.

Set 1: 16 divers, divided into two equal groups (A and B). Dive to 42 msw during 10 min with a safety stop at five msw during three min. Immediately post dive breathing of oxygen (group A) or air (group B) during 30 min. VGE load, time to VGE detection and VGE duration is recorded. Blood samples were obtained pre-dive and 30 and 120 minutes post-dive. After 48 hours, the dives were repeated with switched gases between the groups.

Set 2: 32 divers, divided into two equal groups (A and B). Dive to 42 msw during 10 min with a safety stop at five msw during three min. Fifteen minutes post dive breathing of oxygen (group A) or air (group B) during 30 min. VGE load, time to VGE detection and VGE duration is recorded. Blood samples were obtained pre-dive and 45 and 120 minutes post-dive, from the first 16 divers. After 48 hours, the dives were repeated with switched gases between the groups.

Two further planned sets with repeated diving and shorter duration of oxygen/air-breathing were never carried through.

AE including SAE will be recorded during the study. DCS may be considered either an AE or SAE depending on severity. Ongoing AE and SAE will be followed up.

• Study Type: Interventional
• Enrollment (Actual): 48
• Phase: Phase 2; Phase 3

Contacts and Locations

Study Locations

• Sweden
  • Gothenburg, Sweden, S-416 85
    • Sahlgrenska University Hospital
  • Stockholm, Sweden, S-100 44
    • Kungliga Tekniska Högskolan

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Professional diver
• Fit to dive according to Swedish Navy standards

Exclusion Criteria:

• NONE

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Sham Comparator: Air; Normobaric air breathing	Other: Air
Experimental: Oxygen; Normobaric oxygen breathing	Drug: Oxygen

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Venous gas emboli	Kisman-Masurel grading	120 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Inflammatory activity and endothelial dysfunction	E.g. VCAM-1, ICAM-1	120 minutes/ 48 hours
Decompression sickness	Clinical diagnosis	24 hours
Markers of central nervous system injury	E.g. GFAP, Tau, NfL, UCHL-1	120 minutes/ 48 hours

Collaborators and Investigators

• Sponsor: Göteborg University
• Collaborators: Sahlgrenska University Hospital, Sweden; KTH Royal Institute of Technology; Swedish Armed Forces Diving and Naval Medicine Centre
• Investigators: Principal Investigator: Mikael Gennser, PhD, Kungliga Tekniska Högskolan, Stockholm, Sweden

Study record dates

Study Major Dates

• Study Start (Actual): May 1, 2015
• Primary Completion (Actual): April 1, 2019
• Study Completion (Actual): April 1, 2019

Study Registration Dates

• First Submitted: June 3, 2015
• First Submitted That Met QC Criteria: June 8, 2015
• First Posted (Estimate): June 11, 2015

Study Record Updates

• Last Update Posted (Actual): May 27, 2022
• Last Update Submitted That Met QC Criteria: May 25, 2022
• Last Verified: May 1, 2022

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Pathologic Processes; Wounds and Injuries; Barotrauma; Inflammation; Decompression Sickness
• Other Study ID Numbers: DYK 14-16

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: No

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No