I am glad that your wife has recovered enough to sail.
I have had several experiences that may help. My father in law was in a very similar situation with his wife. He sent a letter along with Doctor notes to Carnival and they allowed him a full credit against a future date. This was several years ago and certainly is a case by case thing. He sailed later and the credit was honored just fine.
I also needed to change the names of travelers once. It cost $50 and was no trouble to do it.
That's great that she has recovered enough to go on the cruise! I'm sure its a relief.
As for the carry on of the O2 equipment, understand that most of the time (if not all of the time) the terminal workers (baggage handlers and security personnel) are not Carnival employees. They work for the local port authority. SO what Carnival claims on their website is the policy of CCL, it may not be the policy of the port security people. I however, would have demanded they check the machine and let you carry it on, I would not have left such a vital piece of medical equipment in the hands of the baggage folks. It could have easily been dropped or broken OR even left behind. None of which would have been a good scenario.
I agree with you about the vital / necessary medical equipment. Somewhat unrelated, my grandmother has a Life Alert type of device. This is a device that is hooked up to your home phone, and has a unit as well as a pendant that you wear either around your wrist or your neck. Last year when I went to go get her to bring her out here, we packed the unit in her suitcase, to carry on. At the airport security line, they just ran her suitcase through the x-ray machine a second time, but didn't question her. Going back home, they didn't have a question about it on this end.
I commented about that to my mom, and our only guess is that accompanying my grandmother back home on this end, that may be a device that the TSA security officers see often, and also, at 90 years old, it's not like my grandmother poses a threat! I guess on my grandmother's end maybe they just wanted to be sure that it was a Life Alert device, but not sure how they could do that just running the suitcase through the x-ray a second time.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)
OldNSalty, I am truly elated your wife recovered enough to make the trip! I know it was extra work for you, but am so glad you all were able to make it. I would think that you should have been able to have carried on your oxygen equipment, but that is truly my opinion. It would be like a diabetic needing their insulin, to me. However, I can also understand needing to go through security. I really don't know what the TSA rules are, but they very well may vary from port to port as the port authority can implement the rules the way they see fit. It's much like the FAA, the rules are interpreted differently by different gateways.
I'm glad you're back and hope that you had an enjoyable and memorable cruise!