The physician orders for CPAP might look like some sort of puzzling code, especially if you are new to CPAP or BiPAP.
In this short guide, we’ll explain what all those numbers on your CPAP prescription mean, after you take a sleep test at home or in clinic. Basically, you’ll learn how to read and understand your CPAP prescription.
Basic CPAP Prescription Examples
A basic order typically looks something like one of these:
- CPAP 6
- BIPAP 15/10
- AUTOPAP (min 4, max 20)
The Mode
The first part of the order indicates the Mode.
Any one of these terms might appear:
- CPAP
- AutoPAP
- AutoCPAP
- BIPAP
- BiLevel
- Auto BiPAP
- Auto BiLevel
CPAP stands for Continuous Positive Airway Pressure.
AutoPAP stands for Automated Positive Airway Pressure, and a synonym for it is AutoCPAP.
BIPAP stands for BiLevel Positive Airway Pressure.
BIPAP is a trademarked term owned by Philips Respironics, but it is used by clinicians frequently regardless of the brand of equipment. BiLevel mode is the “generic” term for BiPAP.
Numerical Values for Pressure
After the mode, the order has some numerical pressure settings. For example,
CPAP 6 = the machine should be set to always deliver 6 centimeters of water pressure.
You breathe in with 6, and you breathe out against the 6. The 6 is continuous, so we call it continuous positive airway pressure (or CPAP).
BiPAP or BiLevel orders add some new vocabulary with the pressure settings. BiLevel therapy uses a lower pressure setting during expiration and between breaths.
Some clinicians refer to that lower pressure phase as EPAP (expiratory positive airway pressure) or PEEP (positive end-expiratory pressure).
BiLevel therapy switches to a higher pressure setting when you breathe in to help you take in a deeper breath or to just make breathing in easier.
The higher pressure setting on inspiration is sometimes called IPAP (inspiratory positive airway pressure) or PS (pressure support).
Technically, pressure support is the difference between the lower pressure and the higher pressure. IPAP is the sum of the lower pressure and pressure support.
BiPAP Prescription Example
The following are all valid BiPAP or bilevel orders, and they all mean the same thing:
- BIPAP 15/10
- BIPAP – IPAP 15 and EPAP 10
- Bilevel – PS 5 and PEEP 10
Auto-BiPAP and Auto-BiLevel Modes
What about those AUTO-BiPAP or AUTO-Bilevel modes?
The pressures move up and down automatically to find the best setting for you at the moment. The difference between the inspiratory and expiratory pressures is the amount of pressure support.
Pressure support is still an ordered parameter. Some newer machines can be programmed to target a volume and are able to auto-adjust the pressure support to target that volume (e.g., AVAPS)
Most still require the pressure support (the pressure gradient differential) to be ordered. Auto-BILEVEL also requires the physician to order guardrails.
Auto-BiLevel Prescription Example
- AUTO-Bilevel, max IPAP 25, min EPAP 7, PS 6
The EPAP is auto-adjusted based on the detection and resolution of airway obstruction but never reduced below 7.
The pressure on inspiration (IPAP) will always measure 6 above the EPAP because the pressure support is ordered at 6.
If the EPAP is titrated to 9, the IPAP will be 15.
This order calls for a minimum EPAP of 7, so the machine must always maintain at least 7 of pressure during expiration and between breaths.
Because the max IPAP is 25, and the PS is fixed at 6, the highest EPAP the machine can titrate to is 19 (25-6=19).
When your machine is set up, it will be programmed to stay in those ranges.
Ramp Setting and Expiratory Release
Your order may also have information relevant to Ramp settings and expiratory release.
Let’s look at an example:
- CPAP 9, Ramp CPAP of 4 for 30 min, expiratory release -2.
Ramp is a feature that lets the device start lower and gradually work its way up as you fall asleep.
The order may specify ramp length or ramp pressures or may simply say it can be configured to patient comfort.
The expiratory release has many different names depending on the manufacturer, but functionally, this is a feature that slightly reduces the pressure during expiration to make it more comfortable to exhale.
If the order is for CPAP of 9, with 2 cm of expiratory pressure relief, you have a pressure of 9 during inspiration but it drops to 7 when you are exhaling.
We hope this brief guide has shed some light on how to read your CPAP prescription.
– Team at Respshop.