(05-16-2015 09:07 AM)nativedancer Wrote: saw dr yesterday. he showed me the graphs and charts from my machine, and said there is no way the 30+ numbers i've been seeing are accurate, machine is "messing up" in that area. i am doing okay, he says, though it make take a while for things to stabilize. sleep oxygen is good now, but actually, he says, i may never reach the kind of plateau that many of you have experienced, and i may ultimately have to settle for a higher ahi median. he raised pressure slightly to 12/22, and last night i slept 6.5 hrs w/out getting up at all. i do continue experiencing some daytime drowsiness and sleeping in the chair, usually about 2 hrs after i have taken my morning lasix, which seems to be the main culprit. dr ordered a follow-up oximeter study in a couple of weeks. see him again in june.
I think you may need a smaller amount of Pressure Support in order to reduce the number of centrals you are having, at least until your prescriptions can be adjusted.
Also, I suggest the EPAP pressure should not be chosen to eliminate all obstructive events but to minimize the AHI. Often patients with lots of centrals will find that a lower EPAP or lower PS will dramatically reduce the number of centrals they have, but may slightly increase the number of obstructive events they are having. So they lower the EPAP and/or PS until they have a lower AHI with an equal balance of central and obstructive events. I think that is all that can be done unless changing to Adaptive Servo Ventilator (ASV) type of CPAP machine which is able to treat both obstructive and central apneas. And, if after balancing their central and obstructive events the AHI or RDI remains worse than 5 (or 10 or whatever - depending on insurance coverage), they are changed to ASV therapy.
Regarding "no way the 30+ numbers i've been seeing are accurate, machine is "messing up" in that area":
Is your doctor dismissing the validity of the data reported by the machine, just because it is different than what he expects or has seen with other patients? Maybe he is good in other areas but is just stubbornly holding to his own opinion in this area, not recognizing that it is known that for a minority of patients bi-level therapy can cause/induce central apneas, especially if the Pressure Support is too high. But I am not sure how COPD changes the available treatment options. Perhaps COPD causes you to need such a high PS? Has the doctor explained why the PS needs to be so high?
By looking carefully at the Flow waveform you can check for yourself whether the apneas reported are valid.
Normally, when an apnea starts the inhale/exhale pattern in the Flow waveform drops off to zero, the machine starts waiting for breathing to resume, and at the end of the apnea the machine records the event and resumes cycling the pressure back and forth between IPAP and EPAP.
Please look closely at the Flow waveform to see this: Zoom in until 5 or 10 minutes fills the screen, and adjust the vertical scale on the Flow waveform to be about -75 Liter/minute to +75 L/m, or perhaps -50 L/m to +50 L/m.
Positive Flow represents the rate (in Liter per minute) at which we are inhaling air into our lungs, and negative Flow is the rate we are exhaling.
Look at each apnea to verify that the inhale/exhale pattern in the Flow has truly dropped near zero during each apnea, and that at these times the Leak was steady and less than about 24Liter/minute.
The only times I have seen that the machine scored an apnea when one had not occurred was during periods of huge Leak or during big changes in the amount of Leak. And this does not happen very often.
When a large leak ends, the machine will keep the pressure steady by reducing the amount of airflow it generates. However, at first, because it takes some time for the machine to properly calculate the change in the leak, the machine will falsely assume that part of the reason that less airflow is needed is because we have started to exhale. The data will show this as the Flow suddenly becoming hugely negative (with our normal inhalation/exhalation pattern still there but falsely offset hugely negative by the inaccurate calculation of changing Leak), and if it takes longer than 10 seconds for the machine's algorithms to correct the mistake it may have decided in the meantime that no inhalations had occurred for 10 seconds and therefore it may have falsely scored an apnea as having occurred. This mistake is more likely to occur if the large leak ends gradually rather than suddenly all at once.
Similarly, when a leak is gradually increasing, the machine will falsely show the Flow becoming hugely positive and may mistake this for an unending inhalation and may falsely score an apnea.
But except for these rare mistakes caused by varying Leak, the data the machines record is very accurate.