(03-18-2014, 02:43 PM)luvkher Wrote: Using a Resmed S9 on "Spontaneous" Mode with 8/4 setting.
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The Leak value is 5/6
Hi luvkher,
I assume a doctor is directing your BiPAP care. I don't know anything about PAP treatment when the patient has had a Tracheostomy. But I can reply to your question about pressure versus leak.
Pressure and Leak are fundamentally different and have different units. So we cannot combine the two as if they were the same type of thing.
It is incorrect to think that the Pressure would be 8 except that 5 or 6 of it is getting lost as Leak. It may be that none of the pressure is lost because of Leak. Even with Leak, the inhale Pressure (IPAP) is likely still 8 and the exhale Pressure (EPAP) is likely still 4.
An example of how Leak does not necessarily lower the Pressure would be when a tire is leaking but an air compressor is connected to the tire and is being controlled to maintain a desired air pressure in the tire. As long as the air compressor exactly keeps up with the amount of leak, the pressure in the tire will remain at its target value.
For CPAP the unit of Pressure is usually centimeters of H2O, which is a very small unit of pressure. For example, it would require hundreds of cm H2O to show at all on most tire pressure gauges.
The bi-level CPAP machine (like any modern CPAP machine) will automatically adjust itself to compensate for Leak and usually will manage to deliver to the patient its target Pressure (8/4 in your case) whether or not there is any Leak, unless the Leak is very huge and the machine is unable to replace the air which is leaking out.
The units of Leak are volume per unit of time, such as Liters per minute. The units of Leak are of the same nature as the units of Flow (airflow), some volume of air per unit of time.
CPAP or BiPAP treatment requires a certain amount of designed-in leakage (vent holes, perhaps like your Leak Valve) which provides at least the minimum needed amount of "intentional" Leak. The total airflow (also called "total Leak") coming from the machine needs to be at least sufficient to supply the minimum needed amount of "intentional" Leak through the mask vent holes (Leak Valve?) to flush out stale air from the patient's mask during exhalation.
If you are not wearing a mask, and if your Leak Valve is leaking air to outside your respiratory system (into the room or outdoors) perhaps your Leak Valve is providing the function usually played by mask vents, and perhaps 5/6 is a setting, meaning that the vent is five-sixths open.
If that is the case, then I would presume that the Leak Valve was adjusted until the ResMed VPAP (bi-level) machine reported a small (but not zero) amount of Leak. On ResMed machines, "Leak" refers to "unintentional" Leak, meaning the amount of leak which is more than the intentional amount of leakage needed to adequately flush out the old air during exhalation. On Respironics machines, "Leak" refers to "total" leakage, meaning a fairly large positive number for "Leak" may be needed to adequately flush out the old air during exhalation.
Take care,
--- Vaughn
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