I have a Phillips Respironics System One. My pressure settings are 4/10. Normally, when I wake up at night, the pressure is around 6-8, and I can tell just by breathing that the machine has increased the pressure. For those that use these machines, you know what it is like when the machine increases the pressure. When I roll over onto my back, my throat closes and the machine ups the pressure to 8-9. When i wake up, I usually push the ramp button to drop the pressure back to 4, roll over, and go back to sleep.
But for the last week I've noticed what when I wake up, this hasn't happened. I wake up, and the machine is idling, no pressure increase. And the low pressure feels lower than usual. I've been using this machine for five years, and I'm very familiar with how it feels at low pressure, and the low pressure is not lower than it should be. I don't have a pressure guage, but I'm thinking of getting one. We have moved recently, so we don't have a supplier or provider here to check it for us.
If I look at the "info" display to see what the 80% pressure is, I see it has dropped from the usual 8.x to 6.x. AHI remains unchanged at about 2.5.
Is this a sign of the machine approaching the end of its life? It has about 5000 hours on it.
You can make a simple water manometer to measure pressure. It's convenient that cpap pressure is measured in cm-H2O.
Just get some clear tubing; make a U-shape bend; put water in such that it will support about 25 cm of water.
Hooked into a tee in your cpap line, the manometer will indicate the pressure by the difference in water column height in cm.
Be sure there is plenty of tubing on the open end to prevent a pressure transient from blowing water out the open end.
Machines are usually replaced at about 5 years; but their design life is about 10 years.
Perhaps you just don't need as much pressure.
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