Drage Dolphin Gas Flow

[RGist]

I have heard several people discuss using a slower gas flow rate than recommended (to extend dive time) and was wondering if many users were using the units in that manner. If so, have you had good results? How did you determine the mix and flow rate?

Thoughts?

 

[bergersau]

STOP!! Messing with jet sizes is NOT a good area for experimentation. The wrong jet could lead to a hypoxic mix......loss of conciousness.....DEATH.

Talk to your Rebreather course instructor in person before playing with this stuff.

 

[Dr. Doug Ebersole]

The unit is designed to be used with either EAN 32, 40, 50, or 60 and using the corresponding flow orifices. The reason for this is so that at a high workload, the diver will not become hypoxic (especially a concern when shallow or at the surface). That having been said, EXPERIENCED Drager Dolphin users have used lower mixes in the cylinder (to allow for a deeper MOD) but lower flow rates (to extend cylinder duration). An example would be a mix of EAN 40 but using the 50% flow. The advantage of this is longer cylinder duration and less "bubbling" as the flows are more "physiologic" for routine diving. The main problem with this approach is the concern of possible hypoxia under high workloads. Also, the rebreather equation which utilizes the gas mix and flow rate to determine what mix you are actually breathing will result in a lower inspired FIO2 which will shorten your no-deco time.

I am an instructor on the Drager Dolphin and would not recommend this approach. That having been said, I often do it myself but with a thorough understanding of what I am doing and what increased risk this entails. Also, I would never consider doing it without a PO2 monitor to know exactly what my FIO2 and PO2 are at every moment during the dive.

 

[RGist]

STOP!! Messing with jet sizes is NOT a good area for experimentation. The wrong jet could lead to a hypoxic mix......loss of conciousness.....DEATH.

Talk to your Rebreather course instructor in person before playing with this stuff.

Understood. I am just asking the question to get a better understanding of how the units are used. Thanks for your feedback.

 

[RGist]

The unit is designed to be used with either EAN 32, 40, 50, or 60 and using the corresponding flow orifices. The reason for this is so that at a high workload, the diver will not become hypoxic (especially a concern when shallow or at the surface). That having been said, EXPERIENCED Drager Dolphin users have used lower mixes in the cylinder (to allow for a deeper MOD) but lower flow rates (to extend cylinder duration). An example would be a mix of EAN 40 but using the 50% flow. The advantage of this is longer cylinder duration and less "bubbling" as the flows are more "physiologic" for routine diving. The main problem with this approach is the concern of possible hypoxia under high workloads. Also, the rebreather equation which utilizes the gas mix and flow rate to determine what mix you are actually breathing will result in a lower inspired FIO2 which will shorten your no-deco time.

I am an instructor on the Drager Dolphin and would not recommend this approach. That having been said, I often do it myself but with a thorough understanding of what I am doing and what increased risk this entails. Also, I would never consider doing it without a PO2 monitor to know exactly what my FIO2 and PO2 are at every moment during the dive.

Your feedback is consistent with what I have been reading. Thanks for your comments.