Cpap

[zzyzx]

Had a call the other day that has me a little puzzled.

Responded to a patient in severe respiratory distress, Hx COPD. I got there after the fire medic had already been on scene for a few minutes. The guy was tripoding on the toilet, ashen, diaphoretic, working really, really hard to breathe. I did not hear any air movement bilaterally.

I was told his sats had been in the 60s when the first medic arrived. The pt's SpO2 was now in the low 90s following a breathing treatment (5 mg albuterol + 0.5 Atrovent). As I stated above, he was still really struggling.

When we got him into the ambulance, I placed him on CPAP with an in-line nebulizer running 5 mg albuterol. During the 10 minute ride to the ER, the SpO2 never got past the high 70s. I double and tripled checked everything, and everything seemed to be working, but his sats did not improve. We held a tight mask seal, the nebulizer was connected to 8 LPM, and the CPAP was working and set to 10 mmHg.

When I got to the ER, they placed him on their CPAP machine, also with an in-line nebulizer, and his sats immediately came up to the high 90s. (As before, he was still working really hard to breathe.) I looked again at our CPAP/nebulizer set up and could not see anything wrong with it.

The only difference was that I had him at 10 mmHg and the RT had him at 20 mmHg. However, I didn't think that that could have made a difference as on scene he was satting in the low 90s on just oxygen and a treatment.

I came back to the ER just a little while later and they were putting a chest tube in his R lung. The xray showed a R lung pneumo.

It bugs me that his sats were so crappy while he was under my treatment, and why they immediately came up in the ER, but I don't see a reason why. I also wonder what caused the pneumo. This was my first time using CPAP on a COPD patient. So here's my question: for you guys that have lots of RT experience or have used CPAP often for COPD patients, do you commonly run such high settings? How safe is it do to so? My thoughts are that this guy popped a pneumo from while having a severe exacerbation of his COPD, not from the high CPAP setting used in the ER, but I'm only guessing, and I suppose there is no way to be sure. Like I said, this was my first time using CPAP on somebody with bronchospasms. It's worked great for the CHF'ers I used it on in the past. I just want to get some thoughts on this call from some of you guys who have a lot of experience with this.

 

[Sublime]

and the RT had him at 20

That's a very high pressure

I have a strong suspicion that this was the culprit. A COPD patient with severe emphysema is more prone to a pneumo caused by CPAP due to loss of elasticity in the lungs.

Did his work of breathing improve with your CPAP machine, or was he still struggling? Did you re-check lung sounds with CPAP on? What were his vitals?

 

[Thricenotrice]

Is mmhg considered the same as cm h2o? No input for why your tx did or did not work, just noticed you calling it a different means of measurement

 

[Clare]

We don't have CPAP but our PEEP valves have a setting of between 5, and I think 20 or 30 cmH2O ... 10 cmH2O is our minimum setting and we go up from there if the patient is not rapidly improving, except in patients who have TBI, then its 5 cmH2O

 

[systemet]

I'm a little confused that a neb treatment brings the sats into the 90s, then they drop into the 70's on your CPAP/neb, then returns to the 90s in the ER.

A neb mask should deliver an FiO2 around 0.6.

http://www.ncbi.nlm.nih.gov/pubmed/20378234

Some of the CPAP ventilators can deliver close to 1.0. Some of the mask delivery devices, e.g. Boussgniac, deliver a variable FiO2 based on inspiratory flow, as they entrain atmospheric air at higher flow rates. Seems like this still probably fair better than a neb mask:

http://www.ncbi.nlm.nih.gov/pubmed/12706763

I wonder if a pneumo developed in the field, was compensated for initially by higher CPAP (20 cmH20?) and then declared itself fully? Just a thought.

The last COPDer I CPAP'd got BiPAP'd in the ER. Not to thread hijack, but anyone know if there's evidence for BiPAP over CPAP in COPD?

 

[ThadeusJ]

The delivered FiO2 will be dependent on the device you are using. The PortO2vent and MACs devices use high output demand valves that are capable of delivering 100% whereas the disposable devices rely on venturis that entrain room air. While the entrained air satisfies the breath and pressure, it must dilute the driving gas of 100% and therefore lower the FiO2. The following link indicates that the most common FiO2 they required was closer to 35% and pressure levels required where split 50:50 between 7.5 and 10 cmH2O:

http://www.ncbi.nlm.nih.gov/pubmed/21805159

Any device you carry cannot compete with the machines used in hospitals. They have infinite control of pressures and FiO2 used to deliver optimal care of the patient but require electricity and infinite amounts of oxygen. Prehospital devices are still evolving and 10 years ago there was nothing to offer the services.

Its more of an art than a science as therapeutic pressures fall in the 5-10 cmH2O range and many if not most services are limited to 10-15 at the high end. Although hospitals can go higher, any patient requiring higher levels is getting into deep water and needs more intensive therapy.

Although pressure therapy can and does lower FiO2 requirements, this isn't carved in stone where it works for each and every patient. Sometimes the best therapy is high FiO2 and minimal pressures. Pressure therapy was first indicated for the recruitment of collapsed alveoli experienced in CHF (and post-op recovery). Studies have shown improvement with COPD and asthma, but not in all cases. Its not an absolute.

 

[jwk]

Is mmhg considered the same as cm h2o? No input for why your tx did or did not work, just noticed you calling it a different means of measurement

No, they are two entirely different units of measure for pressure.

1mmHg = 1.35cmH2O

Ventilatory pressures have traditionally been measured in centimeters of water. It actually represents the pressure exerted by a column of water that is X centimeters tall. I'm not sure the exact reason, but I know that in the dark ages of the mid 60's, PEEP valves could actually be fashioned using a water column in the ventilator circuit. Even today, water seals are used in chest tube systems - on rare occasions you might see chest tube bottles with water seals (what a total PIA those were). We used to measure CVP using a water column device, but that has been abandoned for electronic transducers that usually display mmHg.

Blood pressures and gas pressure measurements have traditionally been measured in millimeters of mercury, and just like cmH2O, represents the pressure exerted by a column of mercury. Standard atmospheric pressure is 760mmHg. You will occasionally see old-fashioned sphygmomanometers with a mercury column used to measure blood pressure. My internist has them mounted on the wall at about where the level of the heart would be for most patients sitting on the exam table.

The metric unit for pressure is a pascal, usually seen as a kilopascal (kPa).
1 Pa = 1 N/m2 (1 Newton per square meter). There is a movement in the scientific community to express all measurements of pressure from whatever source in kPa, and all metrics for that matter, but it is very slow to take hold for pressure measurements. Hey, you still express weight in pounds, right?

 

[Carlos Danger]

Any device you carry cannot compete with the machines used in hospitals. They have infinite control of pressures and FiO2 used to deliver optimal care of the patient but require electricity and infinite amounts of oxygen. Prehospital devices are still evolving and 10 years ago there was nothing to offer the services.

This. Probably just a combination of better equipment and higher pressures.

I'm a little confused that a neb treatment brings the sats into the 90s, then they drop into the 70's on your CPAP/neb

More than once I've seen people's Sp02 improve markedly on a neb, and then as soon as the neb ends their sat drops again.

I don't know why it happens, either.

 

[Christopher]

That's a very high pressure

I have a strong suspicion that this was the culprit. A COPD patient with severe emphysema is more prone to a pneumo caused by CPAP due to loss of elasticity in the lungs.

Did his work of breathing improve with your CPAP machine, or was he still struggling? Did you re-check lung sounds with CPAP on? What were his vitals?

I've never been able to find a case report, outside of neonatal resus or single lung ventilation during surgery, where 10 cmH2O of PEEP from a mask-based CPAP device caused a pneumothorax in a patient.

Not that I think 20 cmH2O isn't excessive...waaay too high!

 

[ThadeusJ]

Blebs and bullae are common in COPD patients and they can rupture spontaneously. I remember speaking to a surgeon who was giving report on a lobectomy patient. He reported that the lung was so friable that every stitch created two more holes which would cause pneumo's. Depending on the extent, any positive pressure could cause it.

 

[Thricenotrice]

No, they are two entirely different units of measure for pressure.

1mmHg = 1.35cmH2O

Ventilatory pressures have traditionally been measured in centimeters of water. It actually represents the pressure exerted by a column of water that is X centimeters tall. I'm not sure the exact reason, but I know that in the dark ages of the mid 60's, PEEP valves could actually be fashioned using a water column in the ventilator circuit. Even today, water seals are used in chest tube systems - on rare occasions you might see chest tube bottles with water seals (what a total PIA those were). We used to measure CVP using a water column device, but that has been abandoned for electronic transducers that usually display mmHg.

Blood pressures and gas pressure measurements have traditionally been measured in millimeters of mercury, and just like cmH2O, represents the pressure exerted by a column of mercury. Standard atmospheric pressure is 760mmHg. You will occasionally see old-fashioned sphygmomanometers with a mercury column used to measure blood pressure. My internist has them mounted on the wall at about where the level of the heart would be for most patients sitting on the exam table.

The metric unit for pressure is a pascal, usually seen as a kilopascal (kPa).
1 Pa = 1 N/m2 (1 Newton per square meter). There is a movement in the scientific community to express all measurements of pressure from whatever source in kPa, and all metrics for that matter, but it is very slow to take hold for pressure measurements. Hey, you still express weight in pounds, right?

I was only saying that to nitpick the OP and be an arse, but thanks for the lesson! Never knew why it was called cmH2O

 

[Sublime]

anyone know if there's evidence for BiPAP over CPAP in COPD?

From everything I've heard and read, there is no benefit of one over the other. BiPAP is more widely used in the hospital setting because it is more customizable. Some would argue that BiPAP is more comfortable for the patient because it allows them a short rest between breaths.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2706602/

Here's some notable quotes from the article above.

In our experience, mask CPAP was safe, well tolerated, and had similar outcomes and effectiveness (relative to medical therapy) as the bilevel non-invasive ventilation interventions in randomized trials.

In another randomized controlled trial among 101 patients with various causes of acute respiratory failure, outcomes with CPAP or BIPAP were similar

Also in two randomized controlled trials in patients with pulmonary edema there was no benefit of BIPAP over CPAP

But as your question was specific to COPD patients, I couldn't find any studies specifically for that. The article above was written in 2006 and included this quote

A randomized trial comparing mask CPAP with other forms of non-invasive ventilation in COPD would be of great interest.

So if anyone is able to find a study of CPAP vs BiPAP in specifically COPD patients... please share!

EDIT: As a small side note to those who didn't know... BiPAP is actually a trademarked name from the company Respironics. As it became a popular device all BPAP (bilevel positive airway pressure) devices started being referred to as BiPAP, whether it was a Respironics product or not. So technically that term is incorrect unless specifically referring to a Respironics machine. Not saying I don't use the term, actually I don't know anyone who actually says "BPAP", but just thought I'd share a little trivia.

 

[Rialaigh]

Just out of curiosity you said in the first part on scene there was no air movement bilaterally. Do you mean you suspected a pneumo on scene? and if so why no decompression? cpap on a patient with a pneumo without decompression (and even with decompression) is going to develope tension and go badly quickly no?

 

[chaz90]

No air movement bilaterally would lead me to think it is more likely that the patient is experiencing a severe broncho reactive airway disease exacerbation. Severely diminished air movement is often auscultated as "no air movement." Before thinking this pt. has some kind of crazy spontaneous bilateral pneumothorax going on I'd look at the more likely diagnosis and corroborate that with blood pressure.

 

[mycrofft]

Get clinical. Call Greg House.

1. On scene, were his efforts more expiratory or inspiratory, or was air moving each way but still felt breathless? (We're putting the negative breath sounds on hold here). (COPD versus other mechanism for inadequate muscular ventilation).

2. Why was he on the toilet? Was he valsalva-ing?

3. Other vital signs? (With #2., rule out or in a cardiac episode).

4. What other factors could contribute to this pt'/s c/o and s/s? What else might have transiently affected the oxygenation? Or the instrumentation?

5. Did he get worse when he was forced to stop "tripoding" and lay down? Get better when moved onto the ED gurney? (positional asphyxia).

Did the first responders tell you why he was given the meds? Was it based upon history or exam?

History, meds, instrumentation, complaints and exam interact, but make sure you know which is doing what, and to what degree.

 

[Handsome Robb]

I read through most of the post so forgive me if it's been said already but I'd be willing to bet their SpO2 dropped because the CPAP device you were using provided a lower FiO2 than the mask with the new treatment.

I know the one we carry, disposable Pulmadyne system we use is in the 30-40% FiO2 range with peep settings of 5, 7.5 and 10.

You'd have to have a pretty big O2 tank on the box to provide CPAP with 100% o2.

Random thought: if you're truly needing a higher FiO2 why not place a nasal cannula at 4-6 lpm in conjunction with the CPAP mask? I know it's less than ideal to remove the mask once it has been placed, a good seal established and secured. I also know that more o2 isn't always the answer. Also, I'm sure some will argue that you may compromise the seal with the NC...our FTOs here are using sidestream cannulas as a trial before they decide if they want to implement them system-wide and from what I'm told none of them have had a problem, seal wise, using the ETCO2 cannula under a CPAP mask.

As far as the pneumo, how was his chest expansion on scene? I don't that it had anything to do with your treatment... 20 Seems a little excessive to me but that's just me... Pretty sure I saw someone else talking about how COPDers are more at risk to pneumos. So take that plus high airway pressures and the risk is definitely there.

 

[Christopher]

I read through most of the post so forgive me if it's been said already but I'd be willing to bet their SpO2 dropped because the CPAP device you were using provided a lower FiO2 than the mask with the new treatment.

I know the one we carry, disposable Pulmadyne system we use is in the 30-40% FiO2 range with peep settings of 5, 7.5 and 10.

You'd have to have a pretty big O2 tank on the box to provide CPAP with 100% o2.

Random thought: if you're truly needing a higher FiO2 why not place a nasal cannula at 4-6 lpm in conjunction with the CPAP mask? I know it's less than ideal to remove the mask once it has been placed, a good seal established and secured. I also know that more o2 isn't always the answer. Also, I'm sure some will argue that you may compromise the seal with the NC...our FTOs here are using sidestream cannulas as a trial before they decide if they want to implement them system-wide and from what I'm told none of them have had a problem, seal wise, using the ETCO2 cannula under a CPAP mask.

As far as the pneumo...I don't that it had anything to do with your treatment... 20 Seems a little excessive to me but that's just me...

I've yet to see any issues with sidestream nasal EtCO2 and concurrent CPAP over the past 3 or so years we've had them in service. Your readings aren't 100% accurate, but they're trendable and give a great RR reading. You can also flow supplemental O2 as you note.

 

[RocketMedic]

Slipstream EtCO2 is awesome. It does not make a difference with the seal and lets me titrate my treatment. You can watch your treatments work. Plus you can run in oxygen.

 

[zzyzx]

Sorry for the late response. Whoops, meant cmH20.

I think his sats may have gotten worse during my transport because of the lower FiO2 with my CPAP. The ER probably used 100% on theirs. That's the only thing that I can think of at least.

He had a silent chest on scene and was still really struggling even when his sats came up to 100% in the ER. I think he had a really bad exacerbation of his emphysema, and popped a bleb before we got there. The CPAP may have made it worse, especially with the higher pressure that the ER used. It's a good thing the transport was short. There would have been no way to figure out without an X-ray that he had a pneumo, and the treatment would only have made it worse.

 

[Carlos Danger]

From everything I've heard and read, there is no benefit of one over the other. BiPAP is more widely used in the hospital setting because it is more customizable. Some would argue that BiPAP is more comfortable for the patient because it allows them a short rest between breaths.

Bipap is much more comfortable, at least at higher inspiratory pressures.

CPAP should only be used in someone with strong respiratory drive and mechanics, whereas bipap is sometimes used in patients whose minute volume is low. A CHF'er with a moderate exacerbation who is just "tired" for instance. Bipap provides support that more closely resembles AC or SIMV on a ventilator.

There is a little less concern with air trapping and dynamic hyperinflation than with CPAP, because the MAP can be lower at similar or even higher inspiratory pressures. Because of those concerns, many clinicians don't like using CPAP on COPD patients (though I don't know anyone who would view intubation as preferable to a CPAP trial).

Once the expiratory pressure begins to be raised to the point that it is approaching the inspiratory pressure, then the mode begins to resemble CPAP and any advantage offered by bipap is lost.