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.