Bilevel Preferred Over CPAP

One thing that continues to puzzle us in our work at our sleep center is how frequently patients are prescribed CPAP when we suspect they should have been initiated with bilevel therapy. We work on 2nd opinion patients quite a bit, and in nearly 90% of cases, the patient presents with a failed response to CPAP. Few if any of these patients ever report that their physicians discussed the potential to use bilevel instead of CPAP. Some had been exposed to auto-CPAP, Cflex, and other expiratory relief systems, but very few had even heard of the term bilevel.

In our clinical experience, where we specialize in mental health patients with insomnia and SDB, we quickly transition the patient to bilevel once they have failed CPAP therapy either initially during the desensitization procedure before the overnight titration or during the titration when it becomes apparent that they are struggling to breathe out against pressurized airflow coming in (expiratory intolerance).

Normal vs Abnormal Expiratory Flow Curve

As promised some weeks back, here is a comparison of two expiratory flow curves, one normal, smooth and rounded (1st Graph) and the other abnormal, choppy, and irregular. These sleep epochs are taken from the same patient who is in stage 2 NREM sleep in the 1st graph and stage 3 NREM sleep in the 2nd graph. These are real sleep epochs taken from a 30-second period from the polysomnogram.

In the 1st graph notice how low the EPAP setting is at 3; whereas in the 2nd graph, the EPAP is now at 4.5, and the curve is no longer smooth but bumpy during this “end-expiration” period.

Now, we can all probably imagine a number of possible explanations for these changes, such as general airflow turbulence or some subtle form of leak, but in our clinical experience the pattern in the 2nd Graph is what we term “Expiratory Intolerance” or “Expiratory Instability.” We believe this description is accurate, because this pattern often emerges during a time when the patient may go on to develop a full-blown iatrogenic central apnea, that is, in response to EPAP, the patient cannot tolerate pressurized airflow coming in as they attempt to breathe out. When this “tension” reaches a tipping point, the patient simply stops breathing.

The pattern shown in the 2nd Graph is most frequently seen in patients on fixed CPAP pressure. And, we find that this expiratory pattern can be relieved by switching the patient to bilevel, through which we attempt to find the lowest possible EPAP that yields a normalized expiratory airflow curve (1st Graph) but which does not cause the jagged curves in the 2nd Graph.

Bilevel Improves Compliance

There’s an article in the Journal of Clinical Sleep Medicine just published about the use of bilevel in treating non-compliant CPAP users. Worth reading and worth appreciating that bilevel is sometimes the superior choice in contrast to straight CPAP.

Holes in Tubes

Today I was cleaning my PAP therapy tubes for my bilevel device, flushing with water, and for the first time I actually saw a thin stream of water squirting out of the side of the tube. I’ve heard of this before, but never seen it, and of course wondered immediately whether or not I was losing significant pressure during the night. Never felt it or sensed it any way, but if there was a difference, hopefully I’ll figure it out tonight…er, tomorrow morning.

Bilevel PAP Therapy Pearls

I started a new topic on bilevel therapy pearls at the CPAP Talk Forum and hope to add to it regularly over the next few weeks.