Q: Leak Rate and Total Leak

[DaveDzRochNY]

Hello all...

If this has been asked before, my apologies.

I have seen a number of SleepyHead graphs that show "Leak Rate" and "Total Leak" data.
But all I see is plain old "Leaks" in my reports.

Is it an option I'm not finding in the software? Or is it because the software does not have
the capability to discern between the two due to my mask (Puritan Breeze)? Or... something
else?

Thanks for any insight!

[robysue]

I have seen a number of SleepyHead graphs that show "Leak Rate" and "Total Leak" data.
But all I see is plain old "Leaks" in my reports.

Your signature shows you are using a Resmed S9. The Resmed S9s record only the unintentional leak rate which is shown as "Leak Rate" in SleepyHead. The Total Leak rate is not recorded by the S9, and hence SleepyHead cannot display the Total Leak rate for S9 users.

Other machines, such as the PR System Ones, record the Total Leak rate. The "Leak" graph for these machines is computed by SleepyHead using statistical analysis of the Total Leak rate data.

[DaveDzRochNY]

Your signature shows you are using a Resmed S9. The Resmed S9s record only the unintentional leak rate which is shown as "Leak Rate" in SleepyHead.

Thank you for your reply.

If I understand correctly then, what I am seeing are "real" (unintentional) leaks... pillows askew, mouth breathing, etc. Yes?

[The Latinist]

Your signature shows you are using a Resmed S9. The Resmed S9s record only the unintentional leak rate which is shown as "Leak Rate" in SleepyHead.

Thank you for your reply.

If I understand correctly then, what I am seeing are "real" (unintentional) leaks... pillows askew, mouth breathing, etc. Yes?

What you are seeing is the result of the S9 automatically subtracting from the total leak rate the expected leak rate for the mask profile you have chosen. For instance, if the machine detects 40L of leaks and at your current pressure with a full face mask the machine expects 20L of intentional "leaks" (i.e., the venting that prevents your rebreathing), then the S9 will record 20L of unintentional leaks. Those leaks are, presumably, "real" leaks -- but the machine has no way of directly measuring those.

[JDS74]

The user guide for your mask on page 7 shows a chart of the "Vent Flow" at different pressures. A guide was packed with you mask and you should have a copy.

This is the value for the air that is designed to flow out of the mask to help eliminate excess CO2 gases from being breathed again as you breathe.

For example, at a pressure of 10 cmH2O, your mask vents at the rate of 23 L/min. Any flow above that, taking into account your own tidal volume, is unintentional leakage from around the seals, etc.

That amount is what is recorded from your machine provided that you can enter into your machine information that tells the ResMed machine what the vent rate characteristics of your mask are. Since I have never used a ResMed machine where I had access to the set-up information, I don't know how hard or even if you can do this for an non-ResMed mask.

Others on this board will be able to answer the question of how to do that.

[The Latinist]

That amount is what is recorded from your machine provided that you can enter into your machine information that tells the ResMed machine what the vent rate characteristics of your mask are. Since I have never used a ResMed machine where I had access to the set-up information, I don't know how hard or even if you can do this for an non-ResMed mask.

It is easy to set mask type on the S9 from the patient setup menu, but as far as I can tell they all assume that you are using a ResMed mask. ResMed seems to have designed most of their masks in the same category (pillows, nasal, FF, etc) to have a very similar leak profile. But it might be that for another manufacturer the leak profiles would not match ResMed's.

Indeed, in looking at your mask's flow rate information, I see that your mask vents significantly less than any ResMed Mask. Compare your mask to ResMed's P10 mask, also a nasal pillow (note: I estimated the P10 numbers based on the graph of the leak profile from the P10 user guide)

Code: Select all

Pr    Br    P10   Diff

5     16     23     7

8     21     29     8

10    23     33    10

12    25     37    12

15    28     42    14     

18    31     47    16

20    32     49    17

As you can see, if you use the S9's "pillows" setting, the machine is likely to significantly understate your leaks (by the amount in the "Diff" column above). If you had a leak of 10 L/min at 10 cmH2O pressure, the S9 will report a leak of "0 L/min."