M-Series Leaks showing up as Apena's?

[cinco777]

Velbor wrote

The location of the leak is not the issue; hose-mask-airway from an airflow hydrodynamic perspective is all the same system. The size of the leak is the issue. If the machine can compensate for flow loss AT ANY SITE within the CPAP system, and maintain pressure THROUGHOUT THE SYSTEM, then adequate therapy remains available.

I enjoyed your clearly explained reasoning on "the size of the leak" within a semi-closed system (or semi-open system, your choice as to which you prefer) being the prime determinant re adequate therapy being or not being delivered. Your reasoning fits with what I learned as an undergraduate Physics major years ago. Thanks for sharing.

[ozij]

The "goal" of therapy is certainly, as you state, having a patent airway. The "means" of achieving this most certainly IS pressure and leak compensation - that's how CPAP works. "Least resistance" is not the same as "no resistance". In a mouth-wide-open situation, there is no resistance to flow, and no possibility of pressure compensation. In a small/periodic-lip-leak situation, there is resistance to flow, and if the machinery can compensate for the pressure loss due to that restricted and limited flow, adequate therapy is still providable. The machine OFTEN CAN compensate for SOME air being rerouted into the room, as it does for venting and small cushion leak - AND small mouth leak.

I have never said or thought that a small periodic leak invalidates therapy. When I talk of "mouth leak" I am referring to 5-10 minute periods in which the mouth is indeed wide open, and there in not enough resistance to create the necessary pressure.. I do not mean "lip leak" when I say "mouth leak".

In a mouth-wide-open situation, there is no resistance to flow, and no possibility of pressure compensation.

Yes, that is what I am talking about. These 5-10 minute periods I'm thinking of do not register on my machine as leaks that exceed the machines ability to compensate - but nevertheless, the pressure can't exist. I am indeed referring to those situations in which there is nor resistance.

The machine OFTEN CAN compensate for SOME air being rerouted into the room, as it does for venting and small cushion leak - AND small mouth leak.

True. I have no argument with that.

O.

[Silver Pelt]

I suspect that the Resmed machine I use generates false apnea/hypopnea flags when leak rates are changing, even when those leaks are well within the machine's ability to compensate.

BB's experience seems to validate that hypothesis.

I have been using a pulse oximeter to provide independent means of detecting apnea/hypopnea events. The correlation of oximeter with the Resmed data is essentially perfect on nights when the leaks are well controlled. On nights where leaks change substantially, but remain below the machine's ability to maintain pressure, the xPAP machine throws AHI flags while the oximeter sees nothing.