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'''KEF'''
Do you believe there is some connection between UARS and trauma or prior insults to the autonomic nervous system? Such that people with a narrow airway and this trauma are more likely to develop UARS than those with a narrow airway but no existing nervous system dysregulation?
'''Barry Krakow, MD'''
The big issue of how to eradicate the flow limitation, which means to round the airflow curve, theoretically can work with even CPAP even though it usually does not. The big reason CPAP doesn't work is once you get to the higher pressures needed to round the curve, the patient cannot tolerate these settings while exhaling; and for this reason alone bilevel options are needed.
The connections between UARS and psychophysiological events/insults appears to be emerging in the research literature. When we published an article in Sleep & Breathing in 2002, we quoted Series article from 1992/1994 where he showed that artificial arousals to normal sleepers actually worsen their breathing, that is, led to greater upper airway collapsibility. Thus, we have always assumed that traumatic and other stressful life occurrences are factoring into the phenomenon of seeing such high rates of OSA/UARS in PTSD patients. Now, we're seeing other research papers coming out that are either quoting us quoting Dr. Series, or going back to Series articles and quoting his group directly on this same idea, namely, if wake someone throughout the night with arousals does it in fact worsen respiration. So far, things are pointing in that direction
'''Barry Krakow, MD'''
If UAES is a type and the question is UARS, it requires the willingness of sleep physicians to carefully scrutinize the sleep study tracings for the classic flattening shape of the flow limitation curve. Simply put, apneas and hypopneas are easy to spot, but it takes more scrutiny to see a flow limitation event, because the volume decrease is smaller. Nonetheless, here's a very salient clinical pearl. In the 1990s, a group from NYC headed by Dr. David Rapoport showed that even when someone only has flow limitation, that is, no apneas and no hypopneas at all, the patients still suffered from daytime sleepiness that was corrected if not eliminated by aggressive treatment with PAP therapy.
'''Elizabeth Strickler'''
Thank you for the information. Isn't it the pressure support on Bilevel/ABPAP that helps to reduce the flow limitations, by effectively raising IPAP but still having a lower EPAP?
'''Barry Krakow, MD'''
Aerophagia (air swallowing) is a very big deal in PAP patients widely under-recognized and under-treated in many sleep medicine clinics. Just today I was talking with an individual with this problem, so I've decided to write a longer post on it next week or the week after. It's very obvious that most aerophagia has a cause, and if the cause is address there's a good chance it will go away. The most common causes of air swallowing are mask leak according to most sleep experts. In our experience, there are more common causes including underlying leg movements (periodic limb movement disorder), rhinosinusitis, allergic rhinitis, nonallergic rhinitis, mouth breathing, and reflux. A lot of patients with air swallowing may benefit from an ENT evaluation to clarify whether any anatomic findings could explain the air swallowing.
'''Elizabeth Strickler'''
Yes, I've had the experience of CPAP not working to reduce flow limitations to an acceptable level, resulting in arousals.
'''KEF'''Do you believe that “floppy epiglottis” can be a problem that causes/contributes to airway issues in some people? '''Barry Krakow, MD'''
There's no question that floppy tissues create greater susceptibility to OSA/UARS; however, in the epiglottis area we're getting down to the very bottom portion of the upper airway, so not being an ENT expert, I can't offer an opinion on that region. We do know of course that the soft palate is often targeted as a site of floppiness, which is why many have invested in the idea of surgery in this area. However, both old and new research do not provide encouraging results for those who undergo soft palate surgeries.
'''Candace Cain'''
Could the higher pressures needed to round the airflow curve lead to air swallowing?
'''Barry Krakow, MD'''
Correct on the issue of higher CPAP leading to discomfort on expiration. When we first starting using bilevel about 15 years ago (we stopped prescribing CPAP in 2005), we saw some very large gaps between IPAP and EPAP. Some patients would like 18/10 or even 18/8. In a few years when we were working with auto-bilevel (ABPAP), we noticed the gaps from pressure support were clearly narrower but rarely would they be 3, which often explains why expiratory pressure support of 3 is not that effective. A typical ABPAP patient might start out with 12/7 and Pressure Support of 3 or 4 when first prescribed, but then months later, these numbers might trend upwards
Unequivocally, higher pressures contribute to air swallowing, but it's often the case that higher pressures are NOT the cause. Does make sense? Probably not, but it appears as if higher pressures are just unmasking some other issue that may not have been recognized as the real culprit of air swallowing. I've worked with many patients who want to and need to lower the pressures because of this problem, but I caution them how important it is to look for other underlying factors, because ultimately the higher pressure might be needed for the best response.
'''Fred Bonjour'''
How much Flow limitation does it take to be significant? When can you say the UARS is treated?
'''Barry Krakow, MD'''
There are generally speaking two types of sleep breathing patients. The first is considered the classic OSA patient who appears to have little anxiety. These patients snore and are sleepy during the day. You can put a mask on them and on night one they adapt instantly to PAP. Guess what? These patients are not very common. They are not rare, but they are not the predominant type of patient with a sleep breathing problem. Therefore, we never saw that many of these classic cases who do fine with CPAP.
'''KEF'''
Do you believe most people have had sleep breathing issues since childhood and if so, what is the best way (if any?) to check for UARS in children?
'''Elizabeth Strickler'''
Does the Pressure Support effectively lower the EPAP (and increase the IPAP)?
'''Barry Krakow, MD'''
Pressure support means the number that stacks on top of EPAP. So if EPAP is 5 and PS is 3 that means your IPAP is going to be 8 during that particular breath. Now, think about auto bilevel: what if your EPAP minimum is 5, but the machine detects you need greater EPAP say 7 because you turned on your back or you went into REM sleep? At that point for the next breaths you get EPAP of 7 but now the IPAP is up to 10 (7 + 3). make sense?
Reply
'''Fred Bonjour'''
To be clear, by rounded you mean it look like an "ideal" breath in the flow rate curve?
'''Barry Krakow, MD'''
I believe a lot more people are suffering from sleep breathing issues at much younger ages than is currently realized, probably because the symptoms are too "mild" to consider as a problem. Nonetheless, it's a shame more attention isn't given, because we would actually see huge improvements in reading skills and other cognitive tasks while seeing a decrease in certain behavioral problems. The issue of UARS diagnosis once again requires sleep docs willing to consider looking at flow limitation on their sleep study tracings.
I, subjectively, feel like I have less aerophagia when using the "for her" APAP setting. Are there algorithms on an Aircurve Vauto that make aerophagia less likely? Also, have you encountered patients who get aerophagia from too low of a pressure (needing more air)?
'''Fred Bonjour'''
To be clear, by rounded you mean it look like an "ideal" breath in the flow rate curve?
'''Barry Krakow, MD20 min agoMD'''
Yes, rounded is optimal and normal. I think the word ideal would come up with sleep professionals who are unwilling to go the extra mile, but in our work we consider the goal was always to round the curve, because that's what normal looks like.
'''Fred Bonjour'''
You have talked about CPAP, APAP, and BiLevel for UARS treatment. What about ASV? if so, when?
'''Barry Krakow, MD'''
ASV is the Cadillac of devices, I believe, because its algorithm has some "magic" embedded within it. Remember, these are proprietary algorithms, so no one but the vendor has access to the info, although researchers try to demonstrate how a particular device might be reacting when it auto-adjusts. In my experience, personally and professionally, ASV is an amazing invention because at times it almost feels like nothing is there. You are just breathing as if there is no pressurized air. I've never felt that with any other device, but I know some people report that experience with other devices. Let me sum up this point by saying that usually 2 out of every 3 patients could do extremely well with ABPAP, but the final third could ONLY do well with ASV, meaning they failed everything else and when placed on ASV, they declared a night and day difference.
'''Barry Krakow, MD'''
Great question on IPAP/EPAP. Most people may not realize that EPAP is generally there to eliminate apneas, but once the apneas are gone, they have now been transformed into hypopneas. Then, if you give more EPAP pressure, the Hypopnea could turn into a flow limitation. Thus, to get from flow limitation to normal breathing, we're talking about the highest possible pressure. That said, usually you raise the EPAP to eliminate apnea and some hypopneas and then we discover that IPAP is more involved in eliminating remaining hypopneas and the flow limitations. For these reasons, it's difficult to fine tune the settings to the optimal or rounded curves, which is why we always brought patients back to the sleep lab to see what it took to round their airflow curves 90% of the night.
once you get apneas down near 0, how much greater pressure is needed typically to eliminate the flow limitation events?
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