Imagine breathing through a straw: inhale, then exhale. The pressure remains constant.
Now inhale normally through your open mouth then exhale through that straw. There’s a pressure difference between when you inhale and exhale. This is the difference between CPAP and BiPAP.
How CPAP and BiPAP make a difference in patients
Continuous positive airway pressure utilizes positive-end expiratory pressure to help splint open the airway structures. PEEP is measured in cmH20, and is commonly utilized in levels such as 5, 7.5 or 10 PEEP during CPAP application. Bi-level positive airway pressure also uses PEEP, but can often afford to utilize it at lower levels than CPAP.
Have you ever wondered why some CPAP patients seem to have a more difficult time breathing when it is first applied? Imagine a COPD, asthma, pneumonia or CHF/pulmonary edema patient sitting forward in a tripod position. Their lips are pursed on exhalation. Your patient is trying to reach for air and create back pressure to keep air pressure in their lungs; they’re creating PEEP.
Indications for PEEP include:
- Rapid respiratory rate.
- Decreased SpO2.
- Increased work of breathing, including accessory muscle use.
- Capnography waveforms indicating bronchospasm or incomplete expiratory phases.
The difference here is that they’re inhaling with one pressure while exhaling against another pressure. In a sense, they’re creating their own BiPAP system. With CPAP, however, the air is forced in at the same pressure, let’s say 10 PEEP, and they’re breathing against that same pressure, so it’s more difficult because there’s no decrease in the expiratory pressure.
BiPAP, on the other hand, takes a more supportive approach, as a patient can inhale with 10 PEEP of support, while only having to exhale against 5 PEEP of back pressure. This pressure difference provides the patient with more comfort and an easier breathing process.
Using CPAP and BiPAP in an EMS setting
Both BiPAP and CPAP are considered non-invasive forms of providing positive pressure ventilation support. What was once reserved for respiratory therapists and other hospital staff to perform has evolved into a common procedure in EMS at both the BLS and ALS levels. In fact, CPAP is considered a standing-order procedure for many EMT providers and systems throughout our country.
How do we determine which patient receives this treatment? A lot of this determination comes down to protocols and available equipment. CPAP has evolved into a completely-disposable product that can be successfully applied in seconds and stored in a compact compartment on your response bag.
BiPAP, however, is still attached to a machine to create the necessary bi-level pressure difference it requires to stick to its definition. While advancements have greatly decreased the size of this equipment, many EMS systems focus on the simplicity of CPAP equipment when determining what is best for their agency.
Regardless of which method you utilize, the results are hard to argue with. The need to intubate a “drowning” pulmonary edema patient, bronchospasming asthma patient or constricted COPD patient has drastically decreased since the utilization of these options in our scope of practice.
We’ve legitimately saved lives through the use of CPAP and BiPAP. Not only do we splint broken bones, we also splint broken airways.
