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Discussion on Tidal Volume
#1
Discussion on Tidal Volume
The following is a continued discussion on Tidal Volume from the following link. http://www.apneaboard.com/forums/Thread-...entilation

To restate my opinion: I don't believe it is necessary to increase tidal volume to 500ml if oxygen levels are in the normal range.
I believe the only time adjustments need to be made in regards to tidal volume is when using a BPAP with Backup. 

Also the 500ml is a target  for a 5'10 155lb male based on a formula of 7ml/kg. There are some in the medical community that believe the formula for those with lung injuries should actually be 6ml/kg. That would put the target at less than 500ml.

My recommendation is if your worried about your tidal volume first check your Oxygen levels. If they are normal than shouldn't worry. However if you find your Oxygen is low than I would talk to your Doctor about it.
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#2
RE: Discussion on Tidal Volume
First off, I'm a xpap uses and have no medical quals of any sort, not even a first aid certificate. All my opinions on xpap have been formed over the last 12 months, from this forum, google and YouTube. (I digest information more easily in a visual, audio form and the speakers normally talk broadly on the subject, often quoting multiple sources and studies.)

From what I've read and seen on youtube. Tidal volume by itself doesn't mean much, it needs to be in context. Respiration rate and minute ventilation are the other arms, when talking about tidal volume. I would limit this discussion to reasonably healthy individuals, that have been approved for machines of 25cm and under. This may include individuals with mild Chronic Obstructive Pulmonary Disease COPD and Obesity Hypoventilation Syndrome. OHS.

For simplicity, I would exclude discussion of those that require a timed or variable back up rate. Those with central nervous system problems of some sort.

I think our original disagreement was about the use of PS of more that 3 or 4 on bpap machines. In response to you post here is
Quote:To restate my opinion: I don't believe it is necessary to increase tidal volume to 500ml if oxygen levels are in the normal range.
What you just said could well be right in a lot of cases. If someone has a RR of 25, with low volume to maintain their o2 in normal range, then I would disagree. What are the respiration rate, minute ventilation and tidal volume that you don't want to adjust from? What is your trigger point, where you would think about more PS than 3 or 4cm?

Quote:I believe the only time adjustments need to be made in regards to tidal volume is when using a BPAP with Backup.

what do you base that belief on?

Quote:Also the 500ml is a target for a 5'10 155lb male based on a formula of 7ml/kg. There are some in the medical community that believe the formula for those with lung injuries should actually be 6ml/kg. That would put the target at less than 500ml.

This would be a group excluded from our discussion, as we are excluding those with serious lung injure/disease and only talking about 25cm and under machines. We aren't talking about the hospital ventilator pressures or the modes used that can cause traumas to these damaged lungs in ICU or one of the respiratory care units. The patient is usually in a coma/induced coma/heavily sedated and on full ventilation

For perspective, we are talking about Vt of 500ml, where a lung holds 6,000ml of air.
again for perspective the ml/Kg of a lung is 80ml/Kg and a full exhale inhale is some 65ml/kg
https://upload.wikimedia.org/wikipedia/e...pdated.png

Have a look at any of the sleepyhead charts, the 95% and max tidal volumes are all well above 500 and I don't think I've seen one under 1000. I know I've seen well over 2000, because I can remember thinking that was a big breath. They all seem okay, I think your point isn't relevant for anyone I've seen on the forum.

Quote:My recommendation is if your worried about your tidal volume first check your Oxygen levels. If they are normal than shouldn't worry. However if you find your Oxygen is low than I would talk to your Doctor about it.
If my respiration rate is high, my tidal volume is low. I would worry, even if my O2 levels were right, I would see a doctor. If my o2 was also low, I would ring an ambulance, because I would be in respiratory failure.

My position
See a doctor, why have a high RR and low TV when you have a bpap, why put up with laboured breathing? Or if you are on a cpap and have high RR low TV (insp/exp times can also be out), or a minute ventilation that is out of the norm. See a doctor about what could be wrong and the possibility of moving to a BPAP.

Often I see the PS numbers suggested on the forum be around what an apap can deliver 3cm or a bit more at 4cm, There was a reason it was titrated to the pressure the doctor set. It isn't always a failed cpap with CA moving to an ASV. 4cm is used at the start of a BPAP titration and is adjusted from there, it isn't the default setting.. walla and myself both link the resmed guide, it is a very good bullet point for background information and ideas that you may want to further read up on.
https://www.scribd.com/document/35340282...-Titration

I personally use a variable min PS:5 max PS:16, a fixed PS for me would be PS:9 for 95% of the time
however from resmed on page 22/23, with BPAP the default recommended pressure support for a normal lung is PS:6. The default for an obstructed OHS is PS:8, as well as differences in other settings. *note this is S mode and without back up breathing. Further on in the guide, they talk about titration.
[Image: XC7P5jA.jpg]
[Image: 9t2YIss.jpg]
mask fit http://www.apneaboard.com/wiki/index.php...ask_Primer
For auto-cpap, from machine data or software. You can set the min pressure 1 or 2cm below 95%. Or clinicians commonly use the maximum or 95% pressure for fixed pressure CPAP, this can also be used for min pressure.
https://aasm.org/resources/practiceparam...rating.pdf
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#3
RE: Discussion on Tidal Volume
First I agree with you about the respiratory rate' If it was above 20 on a steady basis I'd check with a Doctor to be sure there wasn't any problems that needed to be addressed.

Also I agree that tidal volume by it's self doesn't mean anything.

That brings us to the use of pressure support for a healthy person in treating sleep apnea.

The ResMed Guide talks about starting at 4 PS during titration for a non backup BPAP. Now the charts you refer to above are from the guide referring to BPAP with backup. It is not in the section dealing with a regular BPAP. Also in the guide it says if centrals are caused by the increased IPAP than it should be reduced back down and than VPAP or ASV should be considered.

Being it is just a guide than why if someone is having centrals at 4 PS and doesn't at 3 PS wouldn't you reduce it? They already have the BPAP so it's not a matter of which machine to pick. By reducing the PS by 1 a problem is solved. Does it always work no.
Is it worth a try? Heck Yeah!
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#4
RE: Discussion on Tidal Volume
I assume you did open and read the referenced pages, from where the PS:6 and PS:8 came from? If you didn't it will be hard if we are talking across one another.
I'm sorry, where on page 22 and 23 does it even mention back up breathing? It is purely a S mode, even on page 24 where it concludes with a a VPAP technology Q&A, again no mention of back up breathing rates.

it starts out
"Patient Setups
These settings are provided as a guideline for initial settings. Individual patients may require further adjustments based on their own conditions. Existing protocols within your facility should always supersede these baseline recommendations.
Please reference the TiControl guide on page 24 for correlating Ti Max/Ti Min settings appropriate for each disease state and adjust based on patient’s resting respiratory rate"
mask fit http://www.apneaboard.com/wiki/index.php...ask_Primer
For auto-cpap, from machine data or software. You can set the min pressure 1 or 2cm below 95%. Or clinicians commonly use the maximum or 95% pressure for fixed pressure CPAP, this can also be used for min pressure.
https://aasm.org/resources/practiceparam...rating.pdf
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#5
RE: Discussion on Tidal Volume
Go look on the preceding page. Page 21 talks about backup.

I found a link to the copy I have of the Sleep guide by Resmed. It's different than your copy. It breaks it down a little better. https://www.resmed.com/us/dam/documents/...er_eng.pdf
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#6
RE: Discussion on Tidal Volume
I think this is getting hard. I'll give it a few more posts and see if it's worth continuing.
How does this relate to vpap patient settings 22 23 and 24, (page 25 moves on to ivaps tech)
It doesn't say or give any indication about back up? There isn't even the default 10 breaths per minute on these patient set up pages. where do you get the idea from, that it doesn't apply to S mode?

page 21, It is an opening reference to the machines that have a Backup rate
"Backup rate, all ResMed Bilevel modes
(not available on VPAP S)
All bilevel modes on S9 VPAP Tx provide a programmable backup rate. The backup rate is manually set in ST, T, PAC and iVAPS modes. It is automatically set in ASV mode."
mask fit http://www.apneaboard.com/wiki/index.php...ask_Primer
For auto-cpap, from machine data or software. You can set the min pressure 1 or 2cm below 95%. Or clinicians commonly use the maximum or 95% pressure for fixed pressure CPAP, this can also be used for min pressure.
https://aasm.org/resources/practiceparam...rating.pdf
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#7
RE: Discussion on Tidal Volume
If you look at the Guide I have posted a link to you it'll clear this up. The settings you showed above are under Respiratory Diseases in my Guide and are for treatment with a BPAP ST.
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Membership in the Advisory Members group does not imply medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.



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#8
RE: Discussion on Tidal Volume
I don't have my ASV Titration study results back yet but I know I was ordered for a PS of 3.  However, I'm wondering what is the harm in dropping it down to see when my CA events start to go back up, then settle in there.  I don't want any more pressure or help than I basically need, I don't need something that completely takes over for my breathing and makes me want to be dependent on it.
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#9
RE: Discussion on Tidal Volume
Thanks for posting that link to the other guide, I haven't see it before. It still has the s9tx as the lab machine, but has pictures of the 10. (I guess that answers the question on how much real difference there is between the s9 and 10)

I think page 5 makes your point most clearly. When it tells what each machine treats. Although there is a crossover with COPD using both S and ST

Those settings are placed at the very end of the guide and agree they relate to the ST. 




Now for a big however, it can also apply to the S mode, if a back up rate isn't required. For example, as well as the already given COPD, not all OHS people need a back up rate either. 

It seems 80% are treated with standard cpap. with 20% needing o2 or bilevel, either S or ST for those where the drive to breathe is impaired.
It would be interesting to know why resmed list their machines and treatment as they do. I guess in a guide, they have to use a broad brush

https://www.hindawi.com/journals/pm/2012/568690/
6. Conclusions
CPAP is appropriate first-line therapy for ambulatory OHS patients with stable chronic hypercapnic respiratory failure. If a trial of nocturnal CPAP titration fails to eliminate substantial oxygen desaturations (e.g., <88% for more than a few minutes each night)—as in roughly 20% of patients [36]-either addition of low-dose oxygen or a bi-level PAP trial are indicated even though the single small study comparing CPAP with bi-level PAP did not demonstrate long-term differences in patient outcomes (see Figure 1). 
Bi-level PAP should begin with EPAP = 4–10 cm H2O and pressure support of 4 cm H2O. Increases of one or both pressures in increments of 2-3 cm H2O until desaturations are eliminated, pressure support >10 cm H2O, or patient develops intolerance to therapy. If desaturations persist despite CPAP or bi-level PAP (roughly in 1/3 of patients) [36], supplemental oxygen should be administered during sleep to reach 90% saturations without frequent periods of >95% (to avoid hyperoxia-induced hypercapnia). When bi-level PAP is the chosen modality, some patients can be later safely switched to CPAP alone if they improve clinically. Ultimately weight loss is the definitive treatment. Since patient adherence is critical [36], great care should be taken to titrate therapies carefully and to customize treatment. Most important, noninvasive positive pressure therapies are a bridge to prevent worsening cardiopulmonary failure until patients lose weight; so clinicians must work tirelessly to help these patients lose the weight that is life threatening. With the current available data, noninvasive positive pressure therapies should never supplant endotracheal intubation and PPV for ACHRF if there are absolute indications (e.g., airway incompetence with aspiration, shock, profound excess work of breathing or tachypnea >35 breaths per minute with impending respiratory arrest) for securing the airway. Future studies may help to determine whether there are subsets of patients with ACHRF who benefit from positive pressure therapies, which should be used cautiously for such patients until such data are available.

[Image: 568690.fig.001.jpg]
mask fit http://www.apneaboard.com/wiki/index.php...ask_Primer
For auto-cpap, from machine data or software. You can set the min pressure 1 or 2cm below 95%. Or clinicians commonly use the maximum or 95% pressure for fixed pressure CPAP, this can also be used for min pressure.
https://aasm.org/resources/practiceparam...rating.pdf
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#10
RE: Discussion on Tidal Volume
(12-18-2017, 06:32 PM)Hojo Wrote: I don't have my ASV Titration study results back yet but I know I was ordered for a PS of 3.  However, I'm wondering what is the harm in dropping it down to see when my CA events start to go back up, then settle in there.  I don't want any more pressure or help than I basically need, I don't need something that completely takes over for my breathing and makes me want to be dependent on it.

Hojo, that is an excellent observation. Minimum PS in ASV is perplexing because many people are sensitive to pressure support and it actually increases the CA events.  The PSmin is mainly there for comfort, but if it makes you more dependent on the ASV backup rate, you might be better off at a lower minimum PS which encourages spontaneous breathing.  I think that you have the advantage of being aware of what works best for you, and what can have unwanted side-effects. I'm just so pleased that you finally got on an effective therapy that works and resolves all the weirdness you had before.  You will fine-tune it and make it your own.
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