what is the difference between vpap sv and st

i was was wondering if someone could explain to me in simple terminology what is the diffrence between the vpap st and vpap sv???it might have been discussed before...sorry but needed an update and explained more simply..

about $2000 I think.

<ducks>

Yeah I know that wasn't what you meant but I couldn't resist

starpower wrote:i was was wondering if someone could explain to me in simple terminology what is the diffrence between the vpap st and vpap sv??? it might have been discussed before...sorry but needed an update and explained more simply..

Yes. It's been discussed pretty extensively, But briefly here is a quick and dirty explanation.

Normal BiPAP / VPAP essentially will change the pressure to a higher pressure when you inhale and decrease to the lower pressure when you exhale.

Well, if someone has central sleep apnea they may need a periodic reminder to help restart the breathing process. A simple way to do that is to set a backup time by which you must breathe. If you don't breathe by the end of that timer, the BiPAP ST (or VPAP S/T is ResMed's trademark name for a BiLevel PAP S/T) unit will automatically switch to that inhalation pressure. This will help arouse you enough and you should then breathe.

So, imagine the machine off on the side counting down, making certain you are getting 10 or 14 breaths per minute. (The actual value depends on the outcome of your sleep study). If you fail to breathe, the machine switches pressure to help remind you.

Now imagine there is another machine that will try to help you just completley avoid a central apnea or periodic breathing. That's the VPAP Adapt SV. (That stands for adaptive servo-ventilation). Essentially, as I start to stop breathing, I tend to breathe more and more shallowly. Well, this unit will increase the pressure higher and higher in an attempt to keep the air flowing. So, many times throughout the night my unit will kick the pressure up to 25cm H2O. The lower pressure I use is only 10cm H2O.

But it seems to help stop the central apneas in their tracks!

That's a real simple explanation. There's a lot of research behind the VPAP Adapt SV unit. But it is basically pretty simple.

Hope that helps.

Adding to John's explanation ...

The SV type machine is at its heart a bilevel S/T machine - it can do everything an S/T machine does, which is to deliver 2 pressures (breathe in and breathe out) and provide the timed mode to start switching those two pressures at a minimum rate should the user stop breathing (std bilevels don't have this timed back-up-rate feature).

Both the S/T and th SV assume that when you stop breathing, it is a central. They don't probe your airway to determine if it is an obstruction or a central, they just assume it is a central !. That is because these machines are designed for people with centrals & variations of centrals such as Periodic Breathing. and Cheynes-Stokes Respiration.

It is mandatory that when you are titrated with an SV or S/T machine that your obstructive apneas ARE handled adequately by the epap pressure (breathe out pressure). Put another way, the titration process is to clear all obstructive apneas with epap then adjust ipap to reduce hypopneas BUT TO WATCH OUT FOR CompSA which is the condition that can occur when some folk have their obstructions cleared only to have them turn into centrals once on cpap therapy. S/T machines are ok at clearing CompSA but SV machines are the best.

SV machines have an extra trick, but 1st, like S/T machines they will look for no flow, assume it is a central & use epap-ipap cycling at the back-up rate to try to clear the central. But, the extra trick they have is that they (Vpap Adapt SV) also track the volume of air being breathed & look for a drop below 90% in a 3 min moving window & if that drop is detected they will within that same breath ramp up pressure by up to 3 CMs & repeat that if needed for 3 breaths which almost always brings the user back in line.

This above targetting of volume usually prevents the centrals form even occuring but if one slips through they have the cycling at back-up rate to reinforce the SV pressure support.

Hope this extra persective helps. Don't hesitate to ask for further clarification.

DSM

thank you soo much, explained very well.. i sure do appreciate it from you both

I found this recent discussion -
viewtopic.php?f=1&t=50406&p=463816#p463816

On the top of each forum page under the "Home" icon is the Advanced Search feature where you could find even more info.

GumbyCT wrote:I found this recent discussion -
viewtopic.php?f=1&t=50406&p=463816#p463816

On the top of each forum page under the "Home" icon is the Advanced Search feature where you could find even more info.

Gumby,

That discussion is about AVAPS machine modes - AVAPS is a very different beast from ASV. Also it is referring to Respironics machines which are different in how they work from the Vpap Adapt SV & Vpap S/T.

Cheers

DSM