Therapy for LPR, OSA, and… UARS?

[SarcasticDave94]

Yes, that's a good idea, if you've used a certain setup and it felt OK try it again and build a trend.

[Sleeprider]

Your charts show significantly higher tidal volume during the first 20 minutes leading up to sleep onset and the cluster of central events. I didn't read your linked article, but of course hyperventilation and the associated hypocapnea will reduce respiratory drive and place you much closer to your apneic threshold. If you can find a way to reduce the volume of breathing prior to sleep onset by relaxing, mediating or whatever it takes to reduce your oxygen demand as you go to bed and mask up, your will eventually have much less problem with the sleep onset centrals.

One trick your Vauto allows is to shorten the inspiration time by setting Ti Max to a setting less than 2 seconds. You might try 1.8 or so which will cycle the machine to EPAP sooner. This will cause you to stop these long inspiratory breaths, and reduce the tidal volume. It is a way to manage your unusually high respiratory volume just as you first mask up. I don't think you have a CA problem, but as you surmise a hyperventilation problem that after that central cluster settles to a normal respiratory rate and volume for you.

[hoselife]

Thanks Dave! Glad to hear you think I'm on track. I'll stay the course.

And Sleeprider, it's a relief to hear you think that's indeed what's going on. I do think I have some very low level CA as evidenced by my pre-PAP sleep study, but I suspect it's nothing too crazy and that the real issue is how sensitive my carotid bodies are.

One caveat: before sleep, I think I have a hypoventilation problem rather than a hyperventilation one. It was so unintuitive to me to realize that deep breaths and calming exercises can actually make apnea more likely. By reducing Ti_Max, I'm moving myself closer on the spectrum toward faster and shallower breathing / hyperventilation, which should lower CO2 washout and give me a higher apneic threshold. If this works, I think it could be a useful method for treating treatment emergent centrals. The trigger method is similar to ASV in that its solution to an apneic threshold event is to ventilate it, which is great for momentary O2 saturation but also probably further compounds low-level hypocapnia. Whereas in this situation, by 'titrating my inspiratory length', I'm aiming for greater synchrony with the machine and hopefully a more natural level of CO2 washout to begin with.

[Sleeprider]

Without seeing the minute vent, which is the function of tidal volume and respiration rate, I can't say for sure. Clearly that is more the function that you want to track if you're concerned whether ventilation is abnormally high or low.

[hoselife]

Noted! Here is the minute vent for that last example, and I'll make sure to include it in my upcoming charts once I establish a trend here.

[Sleeprider]

I would argue that is not hypoventilation.

[hoselife]

How does one tell using the charts?

[Sleeprider]

Once everything settles out your metabolic needs appear to be met by a minute vent (Vm) of about 5-L/min, but as you first mask up, your Vm is 20 L/min, drops to 9 and increases back to 20 L/min. This hyperventilation is what blew out your CO2 and directly led to the CA events which acted to increase CO2 enough that your respiration rate and tidal volume start to settle, even though your inspiration time is still quite long. Given that Vm tracks Vt, we can assume your respiration rate bpm is fairly constant through here. Anyway, your respiratory volume is easily 3 to 4-times your needs and that is hyperventilation. Higher ventilation as you go to bed is not unusual except for the degree that yours is high and the fact it continues more than 10 minutes. It goes on for 40 to 50 minutes before your hit your sleep volume.

[hoselife]

Thanks for this detailed explanation Sleeprider! I think I get it. I was confusing variety of breath and type of ventilation.

If I'm understanding correctly, the deep, slow breaths I was taking nonetheless technically lead to *hyper*ventilation, because I'm getting vastly more O2 uptake and CO2 clearance than my metabolic needs demand. Limiting Ti_max should also limit my ability to do that before sleep by restricting the "suggested time frame" of my spontaeous inhalation via pressure changes (although I can technically still take high Vt breaths within that timeframe which could mess things up).

[Sleeprider]

I think if we were to looks at a lot of graphs, we would see that most people have initially higher ventilation rates when they first mask up, but most will settle into normal ventilation within about 10 minutes. I think where you get into your apneic threshold is not only the very highly elevated respiratory volume, but the relatively long period of time it takes to come down to something close to your median respiratory rates.