Methoxyflurane Exposure in Ambulances: A Controlled Lab Study on Paramedic Safety

Introduction:
Reintroduced in Canada in 2018, methoxyflurane is a self-administered inhaled analgesic offering rapid, short-term relief for traumatic pain. While low-dose use poses minimal risk to patients, paramedics may face intermittent occupational exposure.

Objectives:
This study evaluates the occupational risks of methoxyflurane exposure to inform paramedic safety, refine occupational health standards, and support the development of a patient care standards.

Methods:
Using thermal desorption tubes, active air sampling was conducted in a controlled laboratory environment within a Ministry of Health-approved ambulance over two days, both with and without ambulance ventilation. Twelve medically screened, consented participants inhaled methoxyflurane for 15 minutes each, following the specified protocol. Air samples were collected in both the driver and patient compartments, adhering to the Environmental Protection Agency (EPA) and International Organization for Standardization (ISO) standards. These samples were analyzed for concentration levels and adjusted for time-weighted averages (TWA) to determine exposure over single and multiple methoxyflurane exposures.

Results:
Twenty-four air samples were collected over two days from participants (median age 30.5 years, 50% female) with similar ventilation rates. Exposure concentrations remained below 8-hour TWA occupational limits and the NIOSH 60-minute ceiling recommended exposure limit (REL). With ventilation on, 8-hour TWA concentrations for a single 15-minute exposure were 0.001 ppm (driver) and 0.033 ppm (patient compartment), rising to 0.017 ppm and 0.057 ppm with ventilation off. Maximum 8-hour TWA concentrations for 22 transports lasting 30 minutes and 15 min exposure, were 0.019 ppm (driver) and 0.736 ppm (patient compartment) with ventilation on, and 0.377 ppm and 1.254 ppm with it off. A significant reduction occurred with ventilation on, with 99.1% protocol adherence and no adverse events.

Conclusion:
This first laboratory-controlled study confirms the safe use of methoxyflurane by paramedics in ambulances, even under worst-case scenarios. Exposure levels remained well below occupational safety thresholds, ensuring paramedic safety and uninterrupted pain management for patients. Adequate ventilation systems within the ambulance significantly reduce exposure risks. These findings support occupational safety standards, enabling paramedics to administer methoxyflurane confidently and ensuring optimal patient care without limitations due to provider exposure concerns.