Posted by Bird Watcher on March 19, 2007 at 19:45:33:

In Reply to: mask type and cpap settings posted by selims on March 19, 2007 at 08:06:50:

This response could get a little long, bear with me. I once used this machine and have done a lot of reading and pondering about them:

You are using a ResMed Autoset Respond APAP, which is the stripped down model from the ResMed Autoset Spirit. The Respond does not record night study data, such as the pressures it develops, leak rates, and AHI figures (like the Spirit does), but it is an auto adjusting CPAP machine, like the Spirit, and has the same response and mask setting choices as the Spirit.

All APAP’s on the market today are at least two machines in one: They can run in CPAP mode or APAP mode. The mode, along with the setting of the pressure (or pressure limits in auto mode) can be done by the clinician. I take it for granted that your machine is set to run in Auto mode.

I have seen the clinician’s manual for the ResMed Spirit and I can mention, without doubt, that there are a few things that it lacks. As a patient, the first and most important thing, I feel, is that it lacks is any auto mode pressure setting guidance to the clinician or physician. Second, it does not disclose to the clinician (or physician) the different responses of each mask mode, and does not disclose any specific facts about the response programming of the machine in auto mode. This ‘response’ is sometimes referred to as the algorhythm.

As a patient, you now are asking questions about the response of the machine you use when two different mask designs are used, and asking yourself why should the response be different? The short answer is that your doctor probably doesn't know, since ResMed doesn’t want to specifically say. However, ResMed is the only manufacturer that has different settings for mask types, so likely, something is changing in the programming when these mask modes are changed. As a reference, I know that neither Puritan Bennett nor Respironics has mask settings for its auto machines.

I think the truth behind auto CPAP’s (although I like and use one) is that they are not
very smart pieces of equipment, don’t deserve to be called auto-titrators (only auto adjusters) and are probably not more than $50.00 worth of parts. I think too many doctors and their patients can place too much faith in the machines to find the correct pressure in auto mode, and generally, get too aggressive and hopeful when it comes time to set the pressure limits.

But they are excellent tools to have at your bedside, in my opinion!!! Read on…

It would be my guess that your breathing flow presents different ups and downs to the machine when you use a FF mask vs. a nasal mask and the machine simply responds differently. Not necessarily correctly, just differently. It can indeed do this if the limits are programmed to be too wide. The machine is capable of running between 4 and 20 cm in auto mode.

I think it’s best for people who want to try AUTO cpaps to already have a firm pressure setting in CPAP mode only and then, when switching over to auto, not to get too aggressive with it. Say, if your lab titration is found to be 10, trust that number and maybe only use 7-10 cm on the auto mode.

If you need to ever use a FF mask again, almost best to get a separate sleep study done with the FF mask and perhaps get a best pressure with a FF mask. Then, only set the auto up for a conservative range from that number.

If you’re fine with your results now, no need to do anything. Just be aware that the ResMed auto’s are:

1. Very sensitive in auto mode and can go over pressure without too much effort, either with a FF or nasal mask.
2. Respond differently in FF or nasal mask settings, but it’s not documented
3. Should never be used with limit settings ‘wide’ open. 4-20 cm is for a wide range of patients and not any one patient.

Follow Ups:

• Re: mask type and cpap settings sleep_physiologist 19:05 3/23/07 (0)
• Re: mask type and cpap settings selims 11:17 3/22/07 (0)

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