Optimal Number of Hyperbaric Oxygen Treatments for Carbon Monoxide Poisoning

Optimizing Hyperbaric Oxygen Treatments for Acute Carbon Monoxide Poisoning: An Open-label Randomized Study.

The optimal treatment strategy with hyperbaric oxygen therapy has been the subject of some debate over the past 3 decades. Initial landmark studies showed a decrease in the incidence of DNS with a single treatment and also with three treatments over the course of 24 hours. These two strategies have continued to be used widely without further evidence comparing them in a direct fashion. Retrospective publications in the years since have been largely conflicting about the benefit of additional hyperbaric treatments. The investigators would seek to randomize patients with carbon monoxide poisoning to receive with 1 or 3 treatments with hyperbaric oxygen and measure their neurologic outcomes.

Study Overview

• Status: Terminated
• Conditions: Carbon Monoxide Poisoning; Hyperbaric Oxygen Therapy
• Intervention / Treatment: Procedure: Hyperbaric Oxygen Therapy; Procedure: Hyperbaric Oxygen Therapy

Detailed Description

HBO is a niche treatment modality, especially in Canada. There are few sites which offer this care, and as such, treatment often carries significant logistical challenges. Since 2021, the HBO unit at the Misericordia hospital has averaged 49 patients per year being treated for CO poisoning. This HBO unit provides coverage to patients within Alberta, Saskatchewan, Manitoba, Yukon, and Northwest Territories. Due to the significant barriers to treatment, including the high cost to the public system, it is important to clearly understand how to best treat these patients.

Purpose:

The aim of this study is to assess whether a single treatment session of hyperbaric oxygen is non-inferior to three treatments for patients with acute carbon monoxide poisoning.

• Study Type: Interventional
• Enrollment (Actual): 2
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Alberta
    • Edmonton, Alberta, Canada, T6G2R3
      • University of Alberta

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• All adult (over 17 years old) patients referred to a Hyperbaric Unit for acute carbon monoxide poisoning.

Exclusion Criteria:

• Obtunded
• Mechanically ventilated
• Pregnant
• Incarcerated
• Cognitively impaired (acutely or chronically)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Single HBO treatment; The exact parameters of each dive will be left to individual clinicians. Commonly used treatments would be: 1 treatment: 100% oxygen at 2.8 atmospheres for 30 minutes followed by a 10-minute air break, then 100% oxygen at 2 atmospheres for 60 minutes with one 10-minute air break after 30 minutes	Procedure: Hyperbaric Oxygen Therapy; Three treatments with hyperbaric oxygen therapy. The exact parameters of each dive will be left to individual clinicians. Commonly used treatments would be: Weaver protocol, or similar (i.e. 100% oxygen at 3 atmospheres for 90 minutes with two 10-minute air breaks every 30 minutes. Repeat this every 8 hours until 3 treatments are complete.); Procedure: Hyperbaric Oxygen Therapy; Single treatment with hyperbaric oxygen. Exact parameters left to treating physician but commonly: 100% oxygen at 2.8 atmospheres for 30 minutes followed by a 10-minute air break, then 100% oxygen at 2 atmospheres for 60 minutes with one 10-minute air break after 30 minutes
Experimental: Three HBO treatments; The exact parameters of each dive will be left to individual clinicians. Commonly used treatments would be: 3 treatments: Weaver protocol or similar variation (i.e. 100% oxygen at 3 atmospheres for 90 minutes with two 10-minute air breaks every 30 minutes. This will be repeated every 8 hours until 3 treatments are complete.)	Procedure: Hyperbaric Oxygen Therapy; Three treatments with hyperbaric oxygen therapy. The exact parameters of each dive will be left to individual clinicians. Commonly used treatments would be: Weaver protocol, or similar (i.e. 100% oxygen at 3 atmospheres for 90 minutes with two 10-minute air breaks every 30 minutes. Repeat this every 8 hours until 3 treatments are complete.); Procedure: Hyperbaric Oxygen Therapy; Single treatment with hyperbaric oxygen. Exact parameters left to treating physician but commonly: 100% oxygen at 2.8 atmospheres for 30 minutes followed by a 10-minute air break, then 100% oxygen at 2 atmospheres for 60 minutes with one 10-minute air break after 30 minutes

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Proportion of patients experiencing delayed neurologic sequalae	DNS includes a spectrum of symptoms such as depression, anxiety, memory issues, ataxia, behavioral changes, decreased cognitive function. For CO-poisoned patients who do not succumb to the direct effects of hypoxia, DNS is one of the primary causes of long-term morbidity. The presence of delayed neurologic sequelae as measured by a series of standardized tests. These tests will include digit span (Attention), the Boston Naming Test 15 (aphasia), general orientation and delayed recall (memory), and clock drawing (visuospatial). DNS will be considered present if a patient scores ≥2 SD below the standardized T scores for any neuropsychological test, if they score ≥1 SD below the standardized T scores for 2 or more tests, or if they score ≥1 SD below the standardized T score for any test and self-report poor memory/concentration/attention.	6 weeks and 6 months

Collaborators and Investigators

• Sponsor: University of Alberta
• Investigators: Study Director: Brian Rowe, MD, MSc, CCFP (EM), FCCP, Professor in the Department of Emergency Medicine, Faculty of Medicine & Dentistry, College of Health Sciences, at the University of Alberta

Study record dates

Study Major Dates

• Study Start (Actual): January 24, 2025
• Primary Completion (Actual): February 10, 2026
• Study Completion (Actual): February 10, 2026

Study Registration Dates

• First Submitted: September 26, 2024
• First Submitted That Met QC Criteria: September 27, 2024
• First Posted (Actual): October 1, 2024

Study Record Updates

• Last Update Posted (Actual): March 13, 2026
• Last Update Submitted That Met QC Criteria: March 11, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Chemically-Induced Disorders; Poisoning; Gas Poisoning; Carbon Monoxide Poisoning; Therapeutics; Respiratory Therapy; Oxygen Inhalation Therapy; Hyperbaric Oxygenation
• Other Study ID Numbers: Pro00146529

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