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kaiasgram wrote: But I think the centrals terrify me more because there's NOTHING you can do about 'em

Not true.. people deal with centrals every day. Not as simply maybe but they are dealt with. That's what those high dollar machines do. They give people a little burst (well probably not so little) of air to jump start the respiratory system.

From what I have read...10 to 15 % of the people put on cpap will develop the "central" issue simply from the pressures.
Most commonly these happen at pressures greater than 10...not always but most often. Seems like those that maybe have an increase in centrals with pressures less than 10 also seem to have already had them present on the diagnostic part of the sleep study without a machine. Sometimes the people need to move on to a different machine...sometimes they go away on their own.

You are a long way from thinking of that other high dollar machine but if the need presented...centrals are treatable.

DoriC wrote:

ChicagoGranny wrote:

kaiasgram wrote: I know leaks drive pressure up.

Events "drive" pressure up.

Leaks "drive" flow up.

kaiasgram wrote:ChicagoGranny, can you explain to this newbie what you mean by "Leaks drive flow up" ? I'm not sure I've got the concept of "flow" down yet. Thanks. I think I have a flow graph but it's jut not checked in my SleepHead software. I can check and display it if it would help you guys tell me more about what's going on with my leaks and pressures and flows... oh my!

I think I'm a little confused too?

I think it means this. Pressure is the resistance to flow. When your ariway closes, there is more resistance so pressure goes up. The machine will keep pushing air only up to its max set pressure. Hence, events drive up pressure. When there are leaks, pressure goes down so the machine increases its flow in order to maintain pressure. All machines can do is increase or decrease flow trying to maintain pressure within the set limits. Since the hose and the mask openings are constant the only things that can affect pressure and the machine's flow are leaks and the opening and closing of the airway.

At least that is how I understand it and how a fluids engineer explained it to me. Perhaps others can expalin it better.

tigrpal wrote:

DoriC wrote:

ChicagoGranny wrote:

kaiasgram wrote: I know leaks drive pressure up.

Events "drive" pressure up.

Leaks "drive" flow up.

kaiasgram wrote:ChicagoGranny, can you explain to this newbie what you mean by "Leaks drive flow up" ? I'm not sure I've got the concept of "flow" down yet. Thanks. I think I have a flow graph but it's jut not checked in my SleepHead software. I can check and display it if it would help you guys tell me more about what's going on with my leaks and pressures and flows... oh my!

I think I'm a little confused too?

I think it means this. Pressure is the resistance to flow. When your ariway closes, there is more resistance so pressure goes up. The machine will keep pushing air only up to its max set pressure. Hence, events drive up pressure. When there are leaks, pressure goes down so the machine increases its flow in order to maintain pressure. All machines can do is increase or decrease flow trying to maintain pressure within the set limits. Since the hose and the mask openings are constant the only things that can affect pressure and the machine's flow are leaks and the opening and closing of the airway.

At least that is how I understand it and how a fluids engineer explained it to me. Perhaps others can expalin it better.

Good explanation, thanks. So when there are leaks there is a LOSS of pressure so machine tries to compensate with increased flow, but if airway is still open with no resistance, no increased pressure is needed right?

tigrpal wrote: I think it means this. Pressure is the resistance to flow. When your ariway closes, there is more resistance so pressure goes up. The machine will keep pushing air only up to its max set pressure. Hence, events drive up pressure. When there are leaks, pressure goes down so the machine increases its flow in order to maintain pressure. All machines can do is increase or decrease flow trying to maintain pressure within the set limits. Since the hose and the mask openings are constant the only things that can affect pressure and the machine's flow are leaks and the opening and closing of the airway.

At least that is how I understand it and how a fluids engineer explained it to me. Perhaps others can expalin it better.

Hmm, still working to understand how increased pressure differs from increased flow -- both technically and in terms of how the user experiences these two phenomena.

ChicagoGranny wrote:
Events "drive" pressure up.

Leaks "drive" flow up.

[

tigrpal wrote:
When your ariway closes, there is more resistance so pressure goes up. The machine will keep pushing air only up to its max set pressure.

The pressure does not go up when the airway closes. The machine simply lowers the flow to maintain the set pressure. If the machine senses several events it will begin to raise the pressure.

What I said in my first post simply means when the machine senses events it will raise the pressure above the min pressure to prevent future events. (There is an algorithm that tells the machine exactly when and how to raise the pressure.) In other words, "Events drive pressure up."

My second statement, "leaks drive flow up", simply means when the mask leaks (unintentional leak) the machine will raise the flow in order to maintain the set pressure. (Of course with very high leaks the machine may not be able to raise the flow enough to maintain the pressure.)

But my comments were only directed at the statement,

wrote: I know leaks drive pressure up.

Leaks do not drive the pressure up. Leaks drive the flow up to maintain the set pressure.

Clear as muddy water?

If you want to talk flow mechanics and machine engineering I will bring my husband here another day.

kaiasgram wrote:But I think the centrals terrify me more because there's NOTHING you can do about 'em. I figure with obstructives there are things you can do even in addition to using your machine, like finding best sleeping position. At least your body is TRYING to breathe!

It's not true that you can't fix centrals. Sometimes you can even fix them with manual CPAP. Sometimes it requires ASV.

There are also some times when you body doesn't try to breathe because it doesn't need to. If your O2 and CO2 levels are good, you may not feel the urge to breathe. Remember, it's not a real central unless your O2 saturation drops or you have an EEG arousal, and your CPAP can't sense that.