CPAP & Auto-Peep

[18G]

I'm trying to make sure I understand auto-peep correctly as it applies to patients with COPD/Asthma and the use of CPAP.

Here is my understanding... feel free to add/correct/further clarify

With COPD/Asthma, there is air trapping which translates to auto-peep. The auto-peep creates a positive pressure in the terminal airways at the end of expiration which makes it extremely hard for the patient to inhale (ie increased work of breathing). Normally at the end of exhalation in a normal patient the pressure should be equalized... hence no airflow?

So, the patient has to work extra hard to inhale since they have to overcome this auto-peep pressure to create the pressure gradient to allow airflow in.

Am I right on so far?

... for patients who are refractory to treatment or are already in extremis, application of CPAP works by creating a pressure that is higher than the intrinsic auto-peep pressure... thus creating a pressure gradient allowing better airflow and taking the workload off the patient. With the CPAP exerting the positive pressure, the patient no longer has to expend high levels of energy and experience muscle fatigue to generate this pressure on their own.


All feedback is appreciated...

 

[MediMike]

Interesting!

I've never actually heard the term "Auto-PEEP" before. My understanding of the physiological benefits of CPAP and PPV for asthma patients was always that the PEEP provided by BiPAP/CPAP helped open up the constricted bronchioles, as well as "forcing" air into them. Which I guess is what you're saying by overcoming the Auto-PEEP pressure. The PEEP provided by CPAP/BiPAP and ventilators exerts the same effect as the pursed lip breathing done by COPD/Asthma patients. Thanks for making me learn something new

Kind of an interesting article here: http://www.ccmtutorials.com/rs/peep/page7.htm

 

[fma08]

http://www.jems.com/webinar/cpap/cpap-filling-sails-respiratory

Click on register now then whatever streaming choice for your computer. It's an hour long, but has a ton of great information especially on the physiology side.

 

[emt/ff71185]

It has always helped me to think of it as keeping the reserve volume up to keep the smaller portions of the airways open. Thus allowing a decreased effort by the patient.