What Researchers Did
An expert committee convened by NOAA (with Canadian expert participation) reviewed experimental evidence to determine whether the 1991 oxygen exposure time limits for technical divers using rebreathers at inspired PO2 of 1.3 ATA could be safely extended.
What They Found
Evidence supports that dives with inspired PO2 of 1.3 ATA consisting of up to 240 minutes of active diving followed by up to 240 minutes of resting decompression are associated with acceptably low risk of CNS oxygen toxicity seizures, exceeding the original 180-minute single-exposure limit from 1991.
What This Means for Canadian Patients
For Canadian technical divers and scientific divers using closed-circuit rebreathers, these updated guidelines provide more permissive -- and evidence-based -- dive time limits at the most commonly used constant PO2 setpoint (1.3 ATA), reducing the need to breach limits during long decompression dives.
Canadian Relevance
Canadian experts participated in this guideline committee, and the updated limits are directly applicable to Canadian technical and scientific diving communities.
Study Limitations
The updated evidence base applies specifically to inspired PO2 of 1.3 ATA; there is insufficient data to extend these revised limits to higher oxygen partial pressures used by some rebreather divers.