John,

Sorry to hear about your health. I hope you can get back to work soon.

I want to point out that oxygen bottles won't leak in the cold. Rather, the pressure decreases due to the cold (cold air contracts, lowering the pressure). Take these bottles inside and warm them up, and the pressure will return to where it was the last time they were warm.

Now, if you are depending on oxygen and take your bottle into extreme cold, you could get in trouble when the bottle gets cold. Try warming up your car before leaving, and then keep the bottles near the heater vent.

Also, you need hose/cannula specially designed for cold weather. Try these guys out:  http://softhose.com/  This product stays flexible in cold weather.