# A, B, and Cs of positive airway pressure

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What exactly does CPAP stand for?  Well, CPAP stands for continuous positive airway pressure.  There are, however, 3 types of PAP therapy: A, B, and CPAP. Here we will discuss how these three types of PAP therapy are different.

It really is just a coincidence that these are called APAP, BPAP, and CPAP.  It has really nothing to do with hierarchy nor is it a timeline on when they were invented.  In reality CPAP was the first, then likely BPAP, then APAP.  A stands for autoset, B for bi-level, and C for Continuous.

### APAP

APAP stands for automatic (or AutoSet) positive airway pressure device (APAP, AutoPAP). Sometimes also called AutoCPAP, however this is a misnomer as the pressure is not continuous but rather changes with time.  The type of positive airway pressure automatically adjusts the amount of pressure delivered to the patient.  The APAP machine has a algorithm which measure resistances to flow and increases pressure if it notes increased resistance ( ie snoring).  If the snoring improves by a change  in sleep stage or sleep position, the APAP machine will likely decrease the pressure. The goal is to give the  minimum pressure required to maintain an unobstructed airway.

### CPAP

Well APAP sounds pretty cool.  Why would my doctor give me an CPAP rather than an APAP machine.  The explalination is pressure simple.  In order to qualify for an APAP machine you would have been diagnosed with sleep apnea, obviously.  But, if for whatever reason you were not able to come back for a titration study (2nd part study) then your doctor may chose to put you on APAP rather than have you return to the lab to find your perfect pressure.  Just imagine going to the eye doctor.  If you go to the eye doctor they will try different glasses to arrive at the right prescription.  Its the same with CPAP.  In order to get CPAP we have to try different pressures in the lab until we find the correct one.  Once the right pressure is found then we will set the CPAP machine to a set pressure.

### BPAP

“Ok, I now get APAP and CPAP; what is BPAP?”  Well BPAP stands for Bilevel positive airway pressure (BPAP), the name we usually here is BiPAP which is a trademarked name.  Its like calling all soft drinks Coca-Cola.  The proper term is therefore BPAP (like saying soft drink).  BPAP has specific uses.  It is usually not meant to be first line of therapy, although this is sometimes the case.  Patients at times can not breath out against CPAP.  The fixed (or continuous) pressure is just to uncomfortable.  In this case BPAP provides two pressures.  One on inhalation pressure   (IPAP, the higher pressure) and one  exhalation pressure (EPAP, the lower pressure.)  This translates into a easier exhalation, which mimics more how we breathe.

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