charville, i saw your response but was too busy to answer. i hope you read this.
i don't think it matters if it is hot or cool mist, the important thing is to get the oxygen into the air.
as far as hyberbaric chambers go, they don't create any oxygen, rather they drive existing oxygen deeper into the tissues. if your friends want to get more out of the hyberbaric treatments, tell them to get some ozonated olive oil online, then rub it onto the child's whole body before treatment. then have the child take a bit internally, this will exponentially increase the efficacy of the hyperbaric treatments.