Want to try a different mask...suggestions?

General Discussion on any topic relating to CPAP and/or Sleep Apnea.
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robysue1
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Re: Want to try a different mask...suggestions?

Post by robysue1 » Sun Jun 30, 2024 12:02 pm

McSleepyhead wrote:
Fri Jun 28, 2024 3:47 pm
You can also feel more air pressure using the Siesta compared to the evo when the masks are on and system running - no doubt about it. This being a true statement it can affect the way a mask works/feels.
What you feel is the additional air flow into the Siesta mask as compared to the air flow into the Evora.

It helps to view xPAP therapy as a semi-closed pressurized system comprising the machine, the mask, your upper airway and your lungs. The system is semi-closed because there is a built-in intentional leak rate. In order to maintain a given pressure, the machine has to blow additional air into the semi-closed system at the same rate that air is being lost from the semi-closed system due to the intentional leak rate for the mask. Given no unintentional leaks, the amount of additional air flowing into the mask that is needed to maintain a given pressure depends solely on the intentional leak rate for the mask.

Given the data that ozij posted, if you are using the Siesta, the machine will need to use a greater air flow into the semi-closed system to maintain a given pressure than the it will if you are using the Evora mask.

As an example, let's suppose your therapeutic setting is a pressure of 12 cm H2O.
  • If you use the Siesta, the machine has to blow air into the system at a rate of 41 L/min to maintain the desired pressure.
  • If you use the Evora, the machine has to blow air into the system at a rate of 35 L/min to maintain the desired pressure.
The pressure is the same in both scenarios. But the air flow into the system is not. Some people are more sensitive to the feeling of "a lot" of air being blown into the mask and others are not. It's not (directly) a problem with the pressure; it's a problem with the perception of the air being blown into the system to maintain the desired pressure.

To draw a crude analogy: It's like sleeping under a fan. Some people don't mind sleeping under a fan that is running on high speed (and hence moving a lot of air). Other people really don't like sleeping under fans running on high, but are ok with sleeping under a fan running at a lower fan speed (and hence the fan is moving less air around.)

The perception of air flow into the mask also depends on how much of your body is being directly subjected to that airflow. In general nasal pillows masks have a somewhat smaller intentional leak rate than full face masks, but for many of the people who dislike nasal pillows, the intensity of that relatively lower airflow directly onto the insides of their nostrils is more uncomfortable than the higher airflow hitting their nose and mouth and chin areas of their face. My husband is someone who hates nasal pillows and loves his full face mask (even though he is not a mouth breather) specifically because he dislikes the airflow hitting the insides of his nostrils. I, on the other hand, much prefer the slightly lower airflow of the nasal pillows even though it is concentrated on a small part of my anatomy, specifically because the outside of my nose doesn't get cold from the perception of air being blown at it.

And then there's the perception of the intentional airflow out of of the mask itself: I dislike the feeling of the jet stream exhaust from the Swift FX when it hits my arms and chest. That exhaust flow at my pressures is actually quite modest: The Swift FX's intentional leak rate at 8 cm H20 is 29 L/min. The P10's intentional leak rate at 8 cm H20 is also 29 L/min. But because the exhaust venting for the P10 is diffused, it can at times feel like it is venting little or nothing because there's no jet stream hitting my arms and chest.

In other words, the perception of air flow into and out of a CPAP mask depends on many things, one of which is the intentional leak rate built into the mask by its designers.

In this sense, McSleepyhead may be correct when he/she says:
It is worth considering if someone is looking for "Mask Suggestions".
In general, if someone is complaining that too much air is being blown at them, it may be useful to recommend a mask with a lower intentional leak rate at their prescribed pressure. On the other hand, if someone is complaining that not enough air is coming in, there may be two good choices: Just increase the pressure a bit, which will increase the air flow needed to maintain the higher pressure. Or suggest using a mask with a higher intentional leak rate at the person's therapeutic pressure setting.

McSleepyhead also writes:
Just looking at the vent hole locations and imagining a face inside the masks screams the opportunity for air to vent at a higher CAPACITY :shock: from the EVO. I'll get around to trying the Siesta mask at lower pressure and see if it is more comfortable.
If the air flow into (or out of) the Siesta mask is what is making you uncomfortable, it might be more comfortable to use the Siesta at a lower pressure, but that doesn't mean lowering the pressure is a good idea: If the lower pressure setting is not sufficient to keep your airway open, then lowering the pressure will compromise the efficacy of your therapy and you'll start experiencing hypopneas and apneas because the pressure no longer is enough to prevent your airway from collapsing.

So if the air flow into (or out of) the Siesta mask seems too much at the pressure needed to keep your airway propped open, then you're better off trying to find a mask that has a lower intentional leak rate at your therapeutic pressure than you are lowering the pressure setting on your machine in order to make the Siesta more comfortable.
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