Using BPAP for patients with pulmonary edema

Michael Allison, MD
26th Nov 2020

In the last article, we stressed the early use of continuous positive airway pressure (CPAP) in patients with acute pulmonary edema. You may have been wondering, why the focus on CPAP? Couldn't bilevel positive airway pressure (BPAP) work just as well?

Continuous positive airway pressure creates benefit because the positive pressure increases the intrathoracic pressure—thereby decreasing preload and afterload. Bilevel positive airway pressure should do the same since it is positive pressure, just given at two different levels. Right?

Two hearts. One is showing a decrease in preload and one showing a decrease in afterload. Illustration.

Figure 1. Decreases in preload and afterload are seen as a result of noninvasive positive-pressure ventilation—whether continuous pressure (CPAP) or bilevel pressure (BPAP).

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Is BPAP recommended for pulmonary edema?

Well, let’s take a look at the literature. 

One early study on the use of BPAP in cardiogenic pulmonary edema found that there was an increase in the incidence of myocardial infarction within the group randomized to BPAP. These results presented a reason to use CPAP instead of BPAP. And, a Cochrane review of BPAP versus standard therapy did not find conclusive evidence of benefit. So, the evidence seemed to be in the corner of CPAP. 

However, another Cochrane review found that when CPAP was compared with BPAP in the treatment of pulmonary edema, there was no difference between the two. 

Talk about conflicting literature!

 

So, should I use CPAP and BPAP for pulmonary edema?

If there is no suspicion for acute hypercapnia or elevated carbon dioxide (CO2) in the blood, CPAP is a great choice based on the benefits we've discussed. However, if there is suspicion or evidence of hypercapnia, go with the BPAP mode because of the added benefit of improving ventilation along with oxygenation.

Note about how to choose CPAP versus BPAP for pulmonary edema.

Figure 2. When choosing between bilevel positive airway pressure (BPAP) and continuous positive airway pressure (CPAP), check first to see if hypercapnia is present. If hypercapnia is present, choose BPAP, if not, choose CPAP.

And don’t worry about the previously mentioned association between BPAP and myocardial infarction—it has not been replicated in any subsequent recent trials.

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Recommended reading

  • Berbenetz, N, Wang, Y, Brown, J, et al. 2019. Non-invasive positive pressure ventilation (CPAP or bilevel NPPV) for cardiogenic pulmonary edema. Cochrane Database Syst Rev4: CD005351. PMID: 30950507