CPAP in ASTHMA? Absolute contraindication?

[Av8or007]

Hey

I'm from Ontario, Canada, and I'm really needing an answer to this question.
Firstly, I know that I need to follow the local medical directives, this is a theoretical WHY question.

Is an acute asthma exacerbation an absolute contraindication for normal CPAP (not BiPAP) based on the CURRENT MEDICAL EVIDENCE? Our MOHLTC (ministry of health and long term care) standards state that asthma is an absolute contraindication to cpap, since according to the CPAP learning package:
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"Asthma
Asthma is the result of an adverse reaction to a stimulus resulting in the contraction of smooth muscle and mucous production in the bronchioles. Stimuli such as an allergen, stress, exercise, and cold weather may cause this increased responsiveness of the bronchi and bronchioles, resulting in bronchoconstriction and mucosal edema. Patients experiencing an asthma attack will present with high pitch wheezing on expiration, tachycardia, tachypnea, positional breathing and in severe cases, cyanosis and Status Asthmaticus (severe asthma attack that is unresponsive to bronchodilators lasting several hours). The use of CPAP for acute asthma has not been well documented in the pre-hospital setting. CPAP in the treatment of an asthma attack may cause increased air trapping and increased intra thoracic pressure, or irritation of the bronchioles further potentiating signs and symptoms. A patient suffering from asthma is in need of treatment with Salbutamol or Epinephrine depending on severity and treatment should not be delayed. As such, CPAP is not indicated for asthma, and is absolutely contraindicated in the presence of asthma exacerbation."
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What I do not understand is that there are many US based EMS agencies using CPAP in asthma and seeing a benefit in PTS that do not respond to meds. Also, they are at least seeing that it does not do harm in most cases, and that there is certainly enough time to discontinue therapy before major problems occur.

Any ideas? I'd like to hear your experiences using CPAP for asthma exacerbation and any relevant studies.

 

[NomadicMedic]

We do use CPAP concurrently with nebulized albuterol, and while I haven't seen a study on its effacy, my anecdotal experience has been that it works like a champ.

 

[Hunter]

We do use CPAP concurrently with nebulized albuterol, and while I haven't seen a study on its effacy, my anecdotal experience has been that it works like a champ.

I think CPAP alone sounds like a bad idea since asthma patients have trouble exhaling air, with albuterol though it might help deliver the medication to the let respiratory tract? Or am I just talking out of my butt?

 

[Handsome Robb]

I think CPAP alone sounds like a bad idea since asthma patients have trouble exhaling air, with albuterol though it might help deliver the medication to the let respiratory tract? Or am I just talking out of my butt?

CPAP alone? Bad idea. CPAP plus a neb is accepted. I had trouble getting my head wrapped around it to but from my understanding you're spot on about "forcing" the treatment into the airways, along with "splinting" the airways open and allowing the trapped air to be exhaled. I've always been taught to start at a low PEEP, think 2.5 mmHg, and work your way up from there.

Ever seen a real bad asthmatic pursed-lip breathing to create auto-PEEP for themselves? Same concept only the CPAP allows them to focus on breathing rather than having to focus on using extra breathing techniques on top of breathing.

Let me know if that makes sense at all, I'm 9.5 hours into my 12 and it's 0145 and I'm sleepy so it may be all gibberish for all I know.

 

[Av8or007]

CPAP alone? Bad idea. CPAP plus a neb is accepted. I had trouble getting my head wrapped around it to but from my understanding you're spot on about "forcing" the treatment into the airways, along with "splinting" the airways open and allowing the trapped air to be exhaled. I've always been taught to start at a low PEEP, think 2.5 mmHg, and work your way up from there.

Ever seen a real bad asthmatic pursed-lip breathing to create auto-PEEP for themselves? Same concept only the CPAP allows them to focus on breathing rather than having to focus on using extra breathing techniques on top of breathing.

Let me know if that makes sense at all, I'm 9.5 hours into my 12 and it's 0145 and I'm sleepy so it may be all gibberish for all I know.

That makes perfect sense. Those PTS need drugs, but CPAP may help deliver the meds. It makes perfect sense to titrate up SLOWLY from a low pressure. What do you think about CPAP after a Salbutamol MDI (repeated doses as necessary) for BLS? Again I'm just curious and will obviously follow all local protocols. Does anyone have a solid paper/study that shows the benefit of CPAP w/ an albuterol neb?

I guess my major question is, is asthma an absolute contraindication or more of a relative contraindication that requires... OMG... CLINICAL JUDGMENT!!!! Back to reality, all i mean is that can CPAP benefit PTS in a acute asthma exacerbation once you've put meds on board.

I'm

 

[Christopher]

Again I'm just curious and will obviously follow all local protocols. Does anyone have a solid paper/study that shows the benefit of CPAP w/ an albuterol neb?

There are a lot of small studies into the potential usage of Noninvasive Positive Pressure Ventilation (NIPPV or NPPV) for the treatment of acute/severe Asthma and COPD, beginning in the early to mid-1990's and extending through today. There doesn't seem to be many larger scale RCT's into the M&M reductions with it.

Shivaram U, et al looked at the cardiopulmonary responses to CPAP in asthma (n=21) and found that CPAP levels at 5-7.5 cm H2O, "were tolerated without deleterious side effects...These data show that application of CPAP in acute asthma reduces respiratory rate and dyspnea with no untoward effects on gas exchange, expiratory airflow, or hemodynamics."

Fernandez MM, et al also looked at NPPV usage in the ICU for status asthmaticus (n=22) and found that it improved alveolar ventilation, decreased the need for intubation, and was effective for the management of patients with severe asthma.

Although from 2002, the only good review of the treatments available for Severe Asthma is Marik PE, et al: The Management of Acute Severe Asthma, and it lays out the literature supporting each indicated treatment.

As it stands there is only LOE B regarding the usage of NPPV for the management of acute severe asthma:

At least fair scientific evidence suggests that the benefits of the clinical service outweighs the potential risks. Clinicians should discuss the service with eligible patients.

To put this in perspective, it seems that magnesium is on most protocols for severe COPD and Asthma, yet only expert opinion and small case reports exist supporting this usage!

Basically: inhaled beta-2 agonists, then NPPV (like CPAP or BiPAP), then anti-cholinergics, then Epi, then corticosteroids.

 

[OzAmbo]

We give the beta 2's via PMDI if the presentation is not too severe. Anticholinergcs are given concurrently with the beta 2's in more severe cases as well as corticosteroids. Adrenaline if they drop their bundle. Magnesium would be tops but i dont have it.

The use of CPAP routineley in asthmatics has my head spinning, i cant figure out the mechanism for providing CPAP in a patient when its intrinsic PEEP that is trying to kill them

I imagine you would have to start with low pressure and work your way up

Response from IMI adrenaline in status patients is amazing

 

[mycrofft]

I can see where a PEEP would help the airways "stay open" against the surface tension and obstruction from fluids exuded into the airway, but it seems a lot of pressure.

Aside, being a cardiac pt myself (a-fib), the epi could do me in. Over a decade before my diagnosis, I knew epi with lidocaine at the dentist gave me chest "tightness", and carbocaine or lido, without, didn't. FOr folks ike me, have something on hand to moderate the epi if needed?

Sidetrack: we used to inject a sustained activity version of epi called "Sus-Phrine". Extended activity, but hold pin to for butt if you couldn't take epi. Maybe that's why it's off the market.

PS: Over the counter epi inhalers (Primatene) were removed form sale after 31DEC'11 due to use of CFC's as a propellant.

 

[Christopher]

The use of CPAP routineley in asthmatics has my head spinning, i cant figure out the mechanism for providing CPAP in a patient when its intrinsic PEEP that is trying to kill them.

I imagine you would have to start with low pressure and work your way up.

I'm going to quote from Shivaram U. et. al. (available in PDF from my Google Drive), the emphasis is mine:

In the past, PEEP and CPAP were often avoided in patients with obstructive airway disease (OAD) because of the risk of barotrauma and adverse hemodynamic effects. However, there are no published reports to support this hypothesis, and on the contrary, recent studies indicate that CPAP or PEEP may help to reduce the work of breathing in patients with OAD.

Later,

This reduction in dyspnea and RR may be mediated through various mechanisms that affect inspiratory and expiratory events. First, CPAP has been shown to reduce the inspiratory work of breathing during acute asthma, as shown by a reduction in the pressure-time product of the inspiratory muscles and in the fractional inspiratory time...Furthermore, during expiration, CPAP may reduce dynamic airway collapse by increasing the intraluminal pressure within the downstream flow-limiting segment, thereby "pneumatically" splinting the airways, which may reduce expiratory airway resistance, improve expiratory airflow, and reduce dyspnea. This mechanism has been postulated to explain the frequent observation of spontaneous exhalation through pursed lips in patients with OAD.

And in regards to gas exchange:

...as assessed by PaO2, PaCO2, and P(A-a)O2 was unchanged with 5 cm H2O of CPAP. Because the airways are inhomogeneously affected by OAD, regional ventilation and time constants may vary widely. CPAP may further distend the previously open airways while recruiting previously collapsed airways and allowing deflation of their corresponding alveolar units...More important, however, is the lack of CO2 accumulation following CPAP, as may be seen when the dead space-to-tidal volume ratio is significantly increased with progressive hyperinflation.

I hope this helps explain why some CPAP is good for COPD/Asthma.

 

[Av8or007]

Another question on physiology, how would BiPAP possibly be better than CPAP in asthma. In Ontario, our air ambulance service will BiPAP asthma PTS, even though the land EMS cannot use CPAP.

How would PEEP (CPAP) be contraindicated (according to our protocols/ALS standards), but PEEP + Pressure support (BiPAP) be used?

 

[DrankTheKoolaid]

re

Taken from the Incredible Dr. Weingart. At the end right before the intubation, its not that the patient can no longer exhale it's that they are so fatigued they can no longer draw in a breath to exhale. Adding pressure support will allow increased tidal volume which will assist with the beta agonist delivery and in a backwards way assist with exhalation

 

[mycrofft]

Spell check typos and haste

For the second time today I'm apologizing for comments that look like I was having a Broca's CVA. I'll try to do better!:blush:

 

[ditchdoc125]

Another question on physiology, how would BiPAP possibly be better than CPAP in asthma. In Ontario, our air ambulance service will BiPAP asthma PTS, even though the land EMS cannot use CPAP.

How would PEEP (CPAP) be contraindicated (according to our protocols/ALS standards), but PEEP + Pressure support (BiPAP) be used?

I wondered this myself... Its quite common to follow the whole algorithm with a asthma patient only for the ED to slap on some BiPAP and fix them... Our protocols state asthma is a contraindication for CPAP as well, but there's the odd medic who will use it concurrently with a combivent neb. Unfortunately our system uses a low-tech CPAP so its 5cm H2O or nothing.

 

[OzAmbo]

I hope this helps explain why some CPAP is good for COPD/Asthma.

Clear as mud

Seriously, perfectly unerstand how CPAP works, i too was under the information that CPAP was absolutely conraindicated in asthma (not COPD) as the mechanism of exudate and bronchospasm in small calibre airways being quite different from the increased alveolar surface tension and loss of surfactant in APO i guess i just took it as gospel.

Interesting reading, i should spend more time in pubmed and CINAHL looking at this stuff :blink:

 

[MSDeltaFlt]

Bare in mind that merely saying COPD you're referencing two common and yet very different diseases: Emphysema and Chronic Bronchitis.

Emphysema (especially end stage) will have the alveoli collapsing. CPAP is great for this in that it can splint the alveoli open improving gas exchange.

Chronic Bronchitis is literally that. Inflammation of the the bronchi and bronchioles (just proximal to the alveoli). Depending on the severity, CPAP can also help splint the airways open improving gas exchange similar to asthma.

Now the kicker here is that CPAP inline with nebs can benefit even more because CPAP will add or keep some pressure against exhalation. What that does is keep the bronchodilator on the lungs a little longer. The longer the drugs stay on the lungs the better they will work.

So, CPAP is not an absolute contraindication to asthma. CPAP is respiratory FAILURE is. And respiratory failure is just before respiratory arrest.

 

[18G]

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.

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.

 

[ZootownMedic]

I had a patient last week that had asthma and COPD. When I got to him he was tripoding, with accessory muscle use, satting at 73% on RA. We gave him a albuterol neb and then a duoneb and we ended up using CPAP enroute. It saved us from intubating him. How would you know if it was a COPD exacerbation or a asthma exacerbation? Audible wheezes? He could have that with both right? Would it even matter? I am not gonna immediately CPAP an asthma patient without a neb first......

 

[46Young]

An absolute contraindication of CPAP is the acute asthmatic would be a total loss of alveolar plateau as observe on the ETCO2 waveform. That's what Bob Page told us at the "Slap the Cap" lecture, anyway.

 

[Doczilla]

We do use CPAP concurrently with nebulized albuterol, and while I haven't seen a study on its effacy, my anecdotal experience has been that it works like a champ.

In line nebulizers are money. I'm guessing OPs system dosent have em

 

[18G]

I had a patient last week that had asthma and COPD. When I got to him he was tripoding, with accessory muscle use, satting at 73% on RA. We gave him a albuterol neb and then a duoneb and we ended up using CPAP enroute. It saved us from intubating him. How would you know if it was a COPD exacerbation or a asthma exacerbation? Audible wheezes? He could have that with both right? Would it even matter? I am not gonna immediately CPAP an asthma patient without a neb first......

During an exacerbation it doesn't matter if it's COPD or asthma. Treatment is going to be the exactly the same and you're not going to be able to definitely say which process is more of the culprit.

Now if the patient is febrile, has had URI S/S the past few days, weakness, chills, etc, then I would lay money on COPD since 75% of COPD exacerbations are the result of a respiratory infection. Chances are though its still a combo of both.

Beta-2 agonists (inhaled and injection - epi or terbutaline), anticholinergic (Atrovent), mag sulfate and steroids (solu-medrol) and CPAP, are treatments that are appropriate and necessary in both COPD and asthma.

Good question.