CSA and OSA regarding software

I have often wondered when my Encore software says I have an OSA event or Hypopnea, couldn't it be a Central Sleep Apnea event?

newyorknative wrote:I have often wondered when my Encore software says I have an OSA event or Hypopnea, couldn't it be a Central Sleep Apnea event?

The Encore Viewer software looks at the indicator written to the SD card by your CPAP machine and the machine decides if it is an OSA or CSA or Hypopnea.

The process starts with the CPAP air flow sensor detecting that the air flow is less that a running average it computes. I don't know the number of breaths is uses but it must be 15 to 30 seconds worth.

Anyway, if the flow is about 40% lower than the running average ( that might not be the exact number and someone will chip in with the exact number and educate us all <hint, hint>) but does not drop below that value, then it creates an Hypopnea event record to be written to the SD card.

If the flow drops really low ( like it stops entirely ), then the CPAP machine ( at least the Respironics ones do ) creates a short puff of pressure at about 0.5 cm H2O to see what happens.

If the pressure reflects back immediately, then the conclusion is that the airway is blocked (OSA) and auto machines up the pressure and try again. It flags that one as OSA and creates an appropriate event record.

If the pressure doesn't reflect back, then it says that's a CSA and creates a CSA event record. The not reflecting back is the result of your airway being open to your lungs and the tiny pressure wave just goes on an dissipates.

The Encore Viewer software just counts the various event records, divides by the number of treatment hours and prints out the OSA index, the CSA index, etc.


It also makes a nice little chart to show you when each of the event types happened so you can match them up with what you remember of the night's sleep in case any of them actually wake youup.