S9 Autoset Sleep Report Stats (and Power Save Mode)

Hi,
I recently got an S9 Autoset after using a PR System One for more than a year. I will be posting a comparative review PRS1 vs. S9 after I get more experience with the S9.

Meanwhile, perhaps someone can please confirm how the stats on the SLEEP REPORT work -- the stats that can be accessed each morning on the screen. I know a lot more data is available with Rescan or Sleepyhead but it is just so convenient to check this each am.

For instance:
AHI 2.8
Total AI 2.3
Central AI 1.8
Leak 1.2 L/min

Is AI just Apneas (obstructive and central) without hypopneas?
If yes, is Total AI - Central AI = 2.3 -1.8 = 0.5 an approximation of obstructive apnea?
And is AHI - Total AI = 2.8 - 2.3 = 0.5 an approximation of hypopneas?
It seems this does all mesh, because then 0.5 (obstructive apnea) + 0.5 (hypopnea) + 1.8 (central apnea) = 2.8, which is the AHI given by the machine.

I will be using Sleepyhead (or Rescan) in the future, but it's just very convenient just to check this report each am.

Also I assume a leak of 1.2L/min is OK (using Mirage FX nasal mask)?

Thanks very much.
Jason

PS I noted a poorly documented item in the clinical manual, you can press the Start/Stop button for 3 secs and the S9 goes into Power Save mode.

Here's a primer for the data that you can get directly off the detailed Sleep Report on the LCD of the S9 Elite and S9 AutoSet.

Let's look at what those AHI, AI, and CAI numbers on your LCD actually mean. Let's suppose your overnight (one day numbers) one morning are:

• 
  For instance:
  AHI 2.8
  Total AI 2.3
  Central AI 1.8
  

And even though the OAI and HI are not shown on the S9's LCD, they're easy to get:

• the OAI = AI - CAI = 2.3 - 1.8 = 0.5
  the HI = AHI - AI = 2.8 - 2.3 = 0.5.

First the AHI, AI, CAI, OAI, and HI are all indices. They indicate how many events of the given type you had per hour on average during the time the machine was on:

• AHI = average number of apneas (all types) + hypopneas per hour the machine was running
• AI = average number of apneas (all types) per hour the machine was running
• CAI = average number of central apneas per hour the machine was running
• OAI = average number of obstructive apneas per hour the machine was running
• HI = average number of hypopneas per hour the machine was running
  

And it helps to know what each kind of event is:

• The S9 will score a hypopnea when your airflow is reduced by at least 50% from baseline lasting at least 10 seconds.
• The S9 will score an obstructive apnea when your airflow is reduced by at least 80% from baseline (i.e. you're not breathing) lasting at least 10 seconds AND the S9 has determined that there is an obstruction in the airway
• The S9 will score an central apnea when your airflow is reduced by at least 80% from baseline (i.e. you're not breathing) lasting at least 10 seconds AND the S9 has determined that there is appears to be no obstruction in the airway
  

The S9 computes each of these numbers (AHI, AI, CAI, OAI, HI) by dividing the number of events (of the particular type) by the time the machine was running. The S9 tells you how long the machine was run overnight in the usage number in Sleep Report. So to continue our example, we'll assume that the usage for the night in question is 7.5 hours. In that case, the number of each type of events the machine recorded for the night can be computed from the LCD data as follows:

• (2.8 events per hour)x(7.5 hours) = 21, (Note that the S9 truncates rather than rounds decimals)
• (2.3 apneas per hour)x(7.5 hours) = 17.25, which equals about 18 apneas that night because the S9 truncates rather than rounds decimals
• (1.8 central apneas per hour)x(7.5 hours) = 13.5, which equals about 14 central apnea that night because the S9 truncates rather than rounds decimals
  

A bit more arithmetic shows that there were likely 3 hypopneas (21 events - 18 apneas = 3 hypopneas) and 7 obstructive apneas (21 apneas - 14 central apnea = 7 obstructive apneas)

The Leak number on the S9's LCD is the 95 percentile unintentional leak rate. Unlike the PR machines, the Resmed machines subtract off the expected leak rate from the raw (total) leak data. Hence all the reported leak rates are UNINTENTIONAL leaks. Resmed engineers claim that the machine can compensate for unintentional leaks as long as they do not stay above 24 L/min for long periods of time.

You said that your machine said:

• Leak = 1.2 L/min

The 95% leak rate = 1.2 L/min means that for 95% of the time the S9 was on, your UNINTENTIONAL leak rate was LESS THAN or EQUAL TO 1.2 L/min. And so for 5% of the night, your leak rate was GREATER THAN or EQUAL TO 1.2 L/min. Now it's important to realize that 5% of one hour is equal to three minutes. If you slept for 7.5 hours, that would mean your leak rate was GREATER THAN or EQUAL TO 1.2 L/min for a grand total of (3 minutes)*(7.5 hours)=22.5 minutes.

And by the way, a 95% leak rate of 1.2 on an S9 is actually a very nice low 95% leak rate.

Finally, I don't know if you are using your S9 AutoSet in CPAP or APAP mode. If you are using CPAP mode, the Pressure number should be equal to your pressure setting. If you ever run in Auto mode, however, the meaning of the 95% pressure level is similar to the meaning of the 95% leak rate: The Pressure setting in the detailed Sleep Quality menu on the LCD is the 95% precentile pressure level---i.e. your pressure was AT or BELOW this pressure for 95% of the time the S9 was running during the night and your pressure was AT or ABOVE this pressure for 5% of the time the S9 was running during the night.

I hope that helps

Robysue -- many thanks for your detailed answer, and all the excellent help you provide everyone in the forum, it is very much appreciated!
Jason

Here is a video that you can look at. it will show you how to get into the advanced information screen. Clinical and all of that stuff. The advanced info screen lets you look at periods of time without ResScan software which is nice.

http://www.cpaplibrary.com/machine-education

Hope this helps,

Dane