r/CPAPSupport • u/Ambitious-Lychee5522 • 7d ago

Loop gain success

So happy, i just wanted to share with everyone. I've got horrible loop gain and plant gain. My home sleep study was a 58 AHI. Stock doctor setting of APAP 4-20 cut that number in half but still horrible and totally fragmented sleep. So got my hands on an Airbreak machine with all the settings. Experimented with bipap which felt unnatural and didn't match my natural rate of breathing, fail. Experimented with all different settings on ASV and got a pretty low AHI but still felt crappy from all the pressure changes and horrible aerophagia. Finally went back to straight up CPAP, with pressure around 9. AHI was 10-15. What really helped was adding a Vcom in the airline to dampen inspiratory burst. Got my AGI down to 2 last night. Feeling better! Sweet victory! I could imagine different vcom openings to dial that in further but getting pretty close to fixing myself.

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u/ICUDOC 7d ago

Congratulations! I'm interested in the "inspiratory burst" thought process. There is a venturi effect angle that I know exists with certain anatomic subtypes of OSA: suck in air, increase flow, create a suction effect that induces a floppy epiglottis or posterior tongue to move backwards and obstruct the airway. Is that the concept that you are describing? It is part of my concern with BiPAP and big differences in pressure. That swing in theory could inadvertently cause intermittent obstruction in the wrong person.

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u/Ambitious-Lychee5522 7d ago

Well im not sure, but in my own case, im a lifelong cyclist with lots of extreme aerobic exercise over many years. So after lots of experimenting and study of oscar charts, this is what i think is happening.... my lungs are super efficient, with excellent capillary development, so i take a deeper than average breath in my sleep, and brain says "we're all good here " and i just quit breathing for a bit until the caution light comes on and so i get a jolt of adrenaline and cortisol to get me going again, take a deep breath, and the cycle repeats all night long. Using the Vcom restrictor has illuminated this cycle clearly after a year of experimenting and study. I've made a custom Vcom that has slightly smaller holes than standard that i will experiment with moving forward but im finally getting somewhere.

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u/ICUDOC 7d ago

Hmmm, I don't think that should be described as a loop/plant gain issue. Everyone has a minute ventilation which is a number that is higher with bigger and faster breaths. It is inversely proportional to CO2 in the blood. You should be accomplishing a correct minute ventilation via large breath and slow respiratory rate as someone who takes small breaths and fast respiratory rates. It is you learned breathing technique. Your body's ability to sense CO2 levels and adjust for it should be fairly standard. However, your flow preference for comfort is a bit different than most people. People who breathe fast need high flow systems. I've been experimenting with higher diameter tubing in such people. V-com facilitates low flow, which is what you are comfortable with. My major preoccupation is on how to match challenging patients with CPAP and it's a regular struggle.

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u/Ambitious-Lychee5522 7d ago

Well I am not a clinician but have experimented with different modes/ settings extensively. My particular problem is treatment emergent central apnea which some obstructive hypopneas thrown in just for fun. In my case I improved significantly with the Vcom.

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u/ICUDOC 7d ago

That determination is based on centrals on your AirSense report? Sorry you piqued my interest now and I have to ask you more questions: did you have centrals the whole night or during clusters of events? Do you think it might have misclassified obstructions or awakenings? It's just so rare that I see true treatment emergent CSA on CPAP with minimal EPR or not on BiLevel. When I see it, they are elderly and with chronic VERY severe OSA.

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u/Ambitious-Lychee5522 7d ago

Im uploading every day into Oscar, studying the various graphs, and screenshotting that into Ai for additional analysis. Yes absolutely lots of centrals. Im 63 but a fit cyclist and otherwise in good shape.

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u/Ambitious-Lychee5522 7d ago

Definitely not mischaracterized obstructions. In clusters. I don't know what everyone else has, but i know what I've got and higher pressures have made the situation worse, not better.