Why do you want a respiratory therapist on hand when giving birth?

?? Respiratory therapists typically aren't on hand for delivery. Exceptions may be if you are expecting a premature infant or an infant that may have a breathing issue. And usually there is a pediatric nurse practitioner or pediatrician present also.
Not necessary. Respiratory therapy is not part and parcel of the birthing process. If you have your baby in a hospital, there will be respiratory therapist available if your doctor believes one is needed. Otherwise it is not included in the general run of things of the birthing process. Breathing exercises are taught by lamaze teachers and others. Generally not a part of respiratory therapy practice.