I will need to use a POC whenever I travel by air. I have done a lot of reading online, and I am almost overwhelmed. There are many, many POCs from which to choose, and I wonder how I will get what is best for me. My pulmonologist will write the orders, but then I will have quite a few choices. I would prefer to try out one or more types of POC before I make a commitment to rent or buy one. Does anyone have helpful tips for a POC virgin?