Pressure Support Question

[MrIvanDrago]

What is the exact purpose of pressure support. Does it effect your CO2 levels in any way? For example, if you went from pressure support of 4.0 to 3.0 or even to 2.0, what effect would it have on CO2 levels if any? 

Or...is it more for comfort? I know someone here will give an excellent and simple answer, so figured I would ask the group. Thank you.

[Sleeprider]

PS, a difference between inspiratory an expiratory pressure, has multiple intentions and benefits. Comfort is certainly part of it as pressure support off-loads the physical effort of inspiration to the machine. At 8 to 10 cm PS all or most of the inspiratory effort is transferred to the machine from the diaphragm, however with obstructive respiratory disease, it may be higher. We want to encourage spontaneous respiration where it is present, so with the exception of central apnea, chronic obstructive respiratory disorders, asthma, or neuromuscular weakness, you won't see PS exceed between 4 and 6 cm in most people. Pressure support can treat upper respiratory resistance syndrome, flow limits, RERA, hypoventilation, periodic breathing, Cheyne Stokes respiration, and central apnea. Pressure support increases ventilation and can be used to increase tidal volume, affect minute vent and respiration rate, however increasing PS and ventilation will purge more CO2, which can affect respiratory drive and cause hypoventilation or central apnea. Individual response varies, however most people will have a threshold of PS at which spontaneous respiration becomes suppressed. For some, that may be with as little as 2-cm of PS or EPR, and with others, much higher. Read the Respiratory Drive wiki for more https://www.apneaboard.com/wiki/index.ph...tory_Drive As a side note, in ventilation we use positive end expiratory pressure (PEEP or EPAP) for oxygenation, and PS for ventilation. PS is the foundation of mechanical ventilation and all forms of respiratory assist devices, and is used for comfort and minor therapeutic effects in CPAP and spontaneous bilevel devices. When we get into bilevel with a backup rate is when we can stimulate breathing in the absence of spontaneous effort and assist in normalizing ventilation in individuals with more serious respiratory disease and impairments.

That's kind of an introduction, so ask any questions.

[Jay51]

First comparing pressure support (PS) to EPAP - say a cpap machine set to a single number (like 7 for instance).  EPAP is the lowest pressure that the machine gets to.  It's purpose is to "stent" or "splint" the airway open at all times (during inhalation, exhalation, and between breaths).  It mainly pertains to OA's (obstructive apneas).  Maybe possibly some H's (hypopneas).  

PS is the pressure in cm/H2O added to EPAP.  So if you had a static EPAP of 7 and PS of 3, your IPAP would reach 10 during peak inhalation.  PS helps reduce or eliminate things that can occur during peak inhalation flow (hypopneas, flow limitations, RERAS, and UARS.)  

It can affect CO2 levels.  There is something called, "co2 washout".  With higher and higher PS, ventilation increases; and more co2 is expelled from the body.  Co2 build up in the body is the key driver of spontaneous respiration.  When CO2 levels get extremely low, CA's (central apneas) can occur.  Also, EPR can contribute to this co2 washout.  

It can also be a comfort feature.  When PS increases, it makes it easier to inhale more fully.  And then when PS decreases and drops back down to the EPAP pressure, than can help to have a more full exhalation - which gets rid of more co2.  

The term "bilevel" means two levels.  EPAP and a PS.  It can also have a back up rate, but that is a different conversation.  

Cpap without EPR would be a single level (just EPAP).

[staceyburke]

Someone may give you a better answer but I got the bilevel (aircurve) because you can’t get pressure support above 3 the resmed 10 or 11 can give (max 3 EPR). It is how you can suppress FL (flow limits) FL are apnea just like o and H events. And resmed increases pressure when it find FL. When my pressure went up I had large leaks that woke me up all night. With increased PS my pressure stayed much lower.

[MrIvanDrago]

PS, a difference between inspiratory an expiratory pressure, has multiple intentions and benefits. Comfort is certainly part of it as pressure support off-loads the physical effort of inspiration to the machine.  At 8 to 10 cm PS all or most of the inspiratory effort is transferred to the machine from the diaphragm, however with obstructive respiratory disease, it may be higher.  We want to encourage spontaneous respiration where it is present, so with the exception of central apnea, chronic obstructive respiratory disorders, asthma, or neuromuscular weakness, you won't see PS exceed between 4 and 6 cm in most people. Pressure support can treat upper respiratory resistance syndrome, flow limits, RERA, hypoventilation, periodic breathing, Cheyne Stokes respiration, and central apnea. Pressure support increases ventilation and can be used to increase tidal volume, affect minute vent and respiration rate, however increasing PS and ventilation will purge more CO2, which can affect respiratory drive and cause hypoventilation or central apnea. Individual response varies, however most people will have a threshold of PS at which spontaneous respiration becomes suppressed. For some, that may be with as little as 2-cm of PS or EPR, and with others, much higher.  Read the Respiratory Drive wiki for more https://www.apneaboard.com/wiki/index.ph...tory_Drive  As a side note, in ventilation we use positive end expiratory pressure (PEEP or EPAP) for oxygenation, and PS for ventilation.  PS is the foundation of mechanical ventilation and all forms of respiratory assist devices, and is used for comfort and minor therapeutic effects in CPAP and spontaneous bilevel devices. When we get into bilevel with a backup rate is when we can stimulate breathing in the absence of spontaneous effort and assist in normalizing ventilation in individuals with more serious respiratory disease and impairments.

That's kind of an introduction, so ask any questions.

Aircurve Settings w/ OSCAR

I have been adjusting my settings recently and after asking questions about pressure support, etc. the last few days, I am attaching my last two nights of OSCAR data. The first night I used PS4.0 and the second night (last night) I used PS3.0. 

Any thoughts around what you can see here, as I slept ok both nights, but my goal as I stated in a previous post is to get close to where my initial CPAP settings were with my Dreamstation 2 with the best possible therapy.

Nov. 19th (VAUTO 13.0/4.0, PS4.0)

   


Nov. 20th (VAUTO 13.0/4.0, PS3.0)

   

[PeaceLoveAndPizza]

Your therapy looks fine with both, you said you slept fine with both, now it’s a matter of personal choice. Regardless of where you were with the Dreamstation, you are in a very good place now.

Unless some significant event happens I suggest continuing using it for another few weeks/months and let’s see how it progresses.

[Sleeprider]

I agree with PLandP. These charts are both excellent and it's up to you to decide what works best. Don't forget your PS is adjustable in increments of 0.2 if you want something in-between.

[MrIvanDrago]

I agree with PLandP. These charts are both excellent and it's up to you to decide what works best.  Don't forget your PS is adjustable in increments of 0.2 if you want something in-between.

Thanks for the advice. Ultimately want to get dialed in to waking up feeling good. With the previous higher pressures I was on, coupled with the PS4.0, the numbers were great, but I felt terrible in the mornings. This is why I was talking about pressure support and if it had something to do with how I was feeling.

[Sleeprider]

With PS 3 and 4 there doesn't appear to be significant residual flow limitation and AHI is near perfect. You're going to be the best judge of what is working at this point. I don't see how your Dreamstation could even get close to this.

[MrIvanDrago]

With PS 3 and 4 there doesn't appear to be significant residual flow limitation and AHI is near perfect. You're going to be the best judge of what is working at this point. I don't see how  your Dreamstation could even get close to this.

Agreed. The Dreamstation 2 is such an inferior machine compared to the ResMed, I don't know how they even stay in business.