Your Question. Where I work, we have a doctor who insists on having the backup rate set at 16-20 on patients with high CO2s. I tried to explain to him that we cannot do this on a BiPAP. Am I right.
My Answer. You are right. BiPAP provides a breath to the patient when a certain flow is sensed. If the patient is breathing at a rate of 10, and you put in a rate of 16, the machine is going to continue to try to force in a breath while the patient is exhaling. All this is going to do is create asynchrony between the machine and patient. It will create little blips on the waveform that do not result in breaths. The BiPAP is going to constantly alarm while this is occurring anyway, so you won't be able to do it for long without irritating the patient, nurses, and probably even yourself.
On the contrary, you can set the backup rate to less than the patient's current rate. For instance, if the patient has a rate of 16 while he is awake, you can set a backup rate at 8. This way, if the patient is sleeping and has apnea episodes, you can be sure the patient will continue breathing. This is okay because the patient won't be exhaling against the machine breath. Obviously you will want the back up rate to be enough to assure adequate ventilation to blow off CO2, although never so high that the BiPAP has a higher rate than the patient's rate when he does start breathing again. Usually, a back up rate of 6-8 is just fine. Although, as always, it's important to create settings that are appropriate for a given patient at a given time.