Hello~I did a Google search, here is what I found.
“Before you begin, ask your doctor if Holotropic Breathwork is safe for you, especially if you have cardiovascular problems, high or low blood pressure, glaucoma, pregnancy, recent surgery, epilepsy, asthma or mental Illness.”
Personally, I would not do it, but, that is up to you, however, it might be wise to have a person who is experienced in this act to be with you, at least for the first few times.