OXY-PEEP for CPAP?

[UMSTUDENT]

I'm having a bit of difficulty understanding something. Recently, one of the systems I work in finally decided to implement CPAP in the CHF protocol algorithm; however, they decided on using a device called the OXY-PEEP by Smiths Medical.

The device is purely a PEEP mask according to the manufacturer's specifications and from my own observations. It allows you to adjust the end expiratory pressure, but does not deliver continuous pressure during inspiration. This has not been my experience with the Emergent PortO2Vent or other devices that I've used or been trained on in the past. While I understand that PEEP is better than nothing at all, I find it hard to justify calling it CPAP on a patient care report.

Am I missing something here? I want to make sure I'm not catching something before I go complaining.

[Medic26]

It looks like a similar set-up to the ones we use. I wouldn't knock em' till you try it. The ones we use are produced by Caradyne (Respironics) with a generator that uses 6 lpm of oxygen to create something like 120 liters of air delivered at 40% oxygen. They work fairly well and our latest protocol allows 10 cm PEEP to start with increase to 15 with medical control order. I was amazed when we first started using them because they really are a simple, almost idiot proof device.

[Dustdevil]

Am I missing something here? I want to make sure I'm not catching something before I go complaining.

All you are missing is semantics, really. PEEP and CPAP are the same action. The difference is that it is called PEEP when it is applied to a patient who is being mechanically ventilated, and CPAP when it is being applied to a patient who is spontaneously self-ventilating. So really, the difference is more in the patient than in the device. Consequently, the terms are tossed about interchangeably in a lot of cases, and there is no real problem with this except to old-school purists.

Technically, if the device you are talking about is a ventilator, you are using PEEP. If it is not a ventilator, and you are using it just to provide positive pressure without ventilation, then it is CPAP.

[UMSTUDENT]

All you are missing is semantics, really. PEEP and CPAP are the same action. The difference is that it is called PEEP when it is applied to a patient who is being mechanically ventilated, and CPAP when it is being applied to a patient who is spontaneously self-ventilating. So really, the difference is more in the patient than in the device. Consequently, the terms are tossed about interchangeably in a lot of cases, and there is no real problem with this except to old-school purists.

Technically, if the device you are talking about is a ventilator, you are using PEEP. If it is not a ventilator, and you are using it just to provide positive pressure without ventilation, then it is CPAP.

There is no inspiratory pressure, only end-expiratory. Only when the patient attempts to breath out is there any pressure on the device. When inspiring, the device is no different to a normal non-rebreather mask. PEEP.

Other CPAP devices I've used deliver pressurized inspiratory oxygen. Your lips and cheeks puff up if you resist against the device. It literally forces a set pressure into your lungs at all times. This device in no way does this.

[Dustdevil]

There is no inspiratory pressure, only end-expiratory. Only when the patient attempts to breath out is there any pressure on the device. When inspiring, the device is no different to a normal non-rebreather mask. PEEP.

That is technically CPAP.

Other CPAP devices I've used deliver pressurized inspiratory oxygen. Your lips and cheeks puff up if you resist against the device. It literally forces a set pressure into your lungs at all times. This device in no way does this.

Pressure to keep the alveoli open is CPAP. Pressure to keep the alveoli open in between ventilator cycles is PEEP.

Both of what you described above are CPAP.

Again, don't get hung up on the semantics, as it is quite normal for the two terms to be used interchangeably, and nobody really cares.

[UMSTUDENT]

That is technically CPAP.

Pressure to keep the alveoli open is CPAP. Pressure to keep the alveoli open in between ventilator cycles is PEEP.

Both of what you described above are CPAP.

Again, don't get hung up on the semantics, as it is quite normal for the two terms to be used interchangeably, and nobody really cares.

Thanks Dust, I understand that both types of device are technically maintaining a continuously positive airway; however, even your friend Dr. Bledsoe's book remarks that they are technically different devices.

True CPAP delivers a positive pressure during inspiration, thus decreasing the work of breathing during the normally active phase of respiration. After inquiring with some friends, it seems that these PEEP devices are a cheaper, more cost effective way to "theoretically" provide the same effect. The problem here seems to occur in that expiration is the normally passive portion of the respiratory cycle. When using PEEP without equal or greater IPAP, or inspiratory pressure, you cause the individual to work to breath out and in. This is counter intuitive to the reasoning many proponents of CPAP tout its use for patients with COPD: to decrease the work of breathing. PEEP devices maintain a continuously positive airway, while the device itself is not continuously positive. PEEP keeps the airway primed due to positive expiratory pressure, whereas true CPAP primes the device and the airway regardless of the effort displayed by the patient.

Per Bledsoe's Essentials of Paramedic Care 2nd Ed., “CPAP is often confused with positive end-expiratory pressure (PEEP). The difference is that PEEP is applied only during respiration, whereas CPAP is applied during the entire respiratory cycle. For this reason, CPAP is the preferred modality for CHF. “Pg. 1223

And

"PEEP uses a restrictive valve on the endotracheal tube or mask of the bag-valve unit. There it resists exhalation, maintaining a positive pressure and keeping the patient's airway open longer during exhalation. CPAP uses special ventilation equipment that increases pressure during both inspiration and expiration. This keeps the airway open during more of the respiratory cycle." Pg. 844

I appreciate the response and agree that this is an effort in semantics to some degree, but I do see an obvious advantage to the device which provides positive inspiratory pressure.

[VentMedic]

This is the biggest problem I'm seeing now with EMS buying CPAP devices. There is a true lack of understanding of the basic principles of work of breathing and how the devices actually work. To save money many companies are going with the cheap CPAP models "for ease of use" and are getting no more than a very low flow device with a lightweight and often ineffective resistive value in line. The salespersons for these devices are seeing some suckers in the field and are making a good sale for themselves.

As mentioned in the last post, PEEP and CPAP are different when explaining effort and work of breathing. Resistive devices such as the PEEP value on the Oxy-PEEP are commonly used as muscle trainers to increase load strenghtening exercises. If used for rescue, enough forward flow would have to be present to overcome the basic design of this device and to meet the patient's inspiratory demand. Hospital CPAP devices are capable of high flows working off of a 50 PSI system with a sensitive demand value for flow adjustments as work of breathing changes. Every patient is different with will have different flow demands and fatique factors. Too much PEEP and inadequate flow will fatique a pt to failure rapidly. Likewise, too much or too little flow can enhance the resistive value and also increase work of breathing to the point of doubling the PEEP value intrinsically.

I'm not knocking any particular name device. I would suggest doing a trial of the device on yourself. See what effort it takes to breathe with this devices on. Many will try them at rest as the salesperson would prefer you did. Try them during or after exercise when you can simulate a little air hunger. See if it can meet your flow demands to breathe with the baseline pressure. A hypoxic and/or ventilation compromised patient may need more than 20 L/M minimum in minute volume in attempts to compensate.

[Dustdevil]

Per Bledsoe's Essentials of Paramedic Care 2nd Ed., “CPAP is often confused with positive end-expiratory pressure (PEEP). The difference is that PEEP is applied only during respiration, whereas CPAP is applied during the entire respiratory cycle. For this reason, CPAP is the preferred modality for CHF. “Pg. 1223

I hope this was a typo on your part, and not how it is actually written in the book. If so, it's pretty poorly written. It would have been much clearer to refer to INSPIRATION or VENTILATION (which are mechanical processes) instead of respiration (which is a chemical process). He often complains about having to dumb his books down to a 9th grade comprehension level, and I think this may be one example of where doing so kind of skewed the results.

"PEEP uses a restrictive valve on the endotracheal tube or mask of the bag-valve unit. There it resists exhalation, maintaining a positive pressure and keeping the patient's airway open longer during exhalation.

Okay, I have to admit up front that RT school was twenty-five years ago for me, so I may be way rusty on this stuff. But it seems what is being described here is not PEEP, but RETARD. Retard is the effect you get from pursed lip breathing. There is no positive pressure applied, just a retardation of the expiratory process. That isn't PEEP. The manufacturers may be calling it PEEP, but technically it is not.

Am I wrong on this, Vent? :oops:

[VentMedic]

DustDevil, you're right on mark with the terminology here.

I usually prefer graphics when trying to explain CPAP and respiratoroy phases.

You just made me reminiscent of Nancy Caroline's Text and the adventures of "Sidney Sinus node" for the dumbing down part. I see it is still presumed that some texts must be written at that level.

"PEEP uses a restrictive valve on the endotracheal tube or mask of the bag-valve unit. There it resists exhalation, maintaining a positive pressure and keeping the patient's airway open longer during exhalation.

Okay, I have to admit up front that RT school was twenty-five years ago for me, so I may be way rusty on this stuff. But it seems what is being described here is not PEEP, but RETARD. Retard is the effect you get from pursed lip breathing. There is no positive pressure applied, just a retardation of the expiratory process. That isn't PEEP. The manufacturers may be calling it PEEP, but technically it is not.

RT principles and fundamentals haven't changed; just a few more knobs and buttons on sleeker looking technology.

They always wanted us to use a PEEP valve on self-inflating bags but I find them a little futile at times. It retards the exhalation phase momentarily but ends before the next breath and the manometer drops to zero. I will run a valve in line with a free flow anesthesia bag (Jackson-Rees system) and try to maintain an elevated baseline with flow..."flow PEEP" from the DOWNES and EMERSON days. There is one disposable CPAP system that reminds me of a DOWNES generator and actually isn't too bad.

There are two devices that I have recently seen on the trucks that are essentially "nebs with a restrictive valve" running on 6- 10 liters off the flowmeter. One patient was being physically restrained to stay on the device. I've been wanting to toss a manometer in line to see what the baseline is holding at with this devices. I've just been too busy switching them to my technology so they can be unstrained and breathe.

[UMSTUDENT]

I hope this was a typo on your part, and not how it is actually written in the book. If so, it's pretty poorly written. It would have been much clearer to refer to INSPIRATION or VENTILATION (which are mechanical processes) instead of respiration (which is a chemical process). He often complains about having to dumb his books down to a 9th grade comprehension level, and I think this may be one example of where doing so kind of skewed the results.

Okay, I have to admit up front that RT school was twenty-five years ago for me, so I may be way rusty on this stuff. But it seems what is being described here is not PEEP, but RETARD. Retard is the effect you get from pursed lip breathing. There is no positive pressure applied, just a retardation of the expiratory process. That isn't PEEP. The manufacturers may be calling it PEEP, but technically it is not.

Am I wrong on this, Vent? :oops:

Sorry Dust, that is a typo on my part. It should read "expiration", not respiration. My bad. I noticed it as soon as you pointed it out.

So for the benefit of Dr. Bledsoe, the correct quote is as follows,

"CPAP is often confused with positive end-expiratory pressure (PEEP). The difference is that PEEP is applied only during expiration, whereas CPAP is applied during the entire respiratory cyle. For this reason, CPAP is the preferred modality for CHF."

It still supports what I was saying, minus my brain fart while copying it from the book.