CPAPtalk.com

Rubicon wrote: ↑

Mon Apr 24, 2023 4:24 pm

There is an interesting relationship between the expiratory unspike (downward spike) in flow and the pressure waveform:



The drop to EPAP overshoots the baseline of 10 cmH2O, causes a pressure bounce and results in a positive fluctuation of about 0.5 cmH2O. IMO the expiratory unspike, heretofore a telltale "PP" sign, is caused by a relative IPAP burst of 0.5 cmH2O, and abruptly shifts the expiratory upwards.

So I want to see if I understand what you are saying.

Here's an edited version of your last figure where I've put red circles around the the unspikes (downward spikes) in both the wave flow graph and the mask pressure graph and I've put blue circles around the spikes (upward spikes) in the mask pressure graph:



You're saying that the unspikes in the flow wave graph in the red circles would ordinarily be a telltale sign of a prolapsed palate, but because of what's going on in the mask pressure graph, they're not?

If I'm understanding what you are talking about, the EPAP overshoots are the unspikes in red circles on the mask pressure graph. The relative IPAP bursts of 0.5 cmH2O are the spikes in the blue circles in the mask pressure graph.

The spikes in IPAP occur right at the end of the inhalation, and it's those spikes I've highlighted in blue on the mask pressure curve that are causing the unspikes in the wave flow data as well as the immediately following upward shift and flattening in the expiration?

But what's causing the unspikes in the mask pressure graph? In other words, why is the machine overshooting the desired EPAP by 0.5 cm on every exhalation? And does the small positive bounce from 9.5 to 10.0 cm of pressure during EPAP cause the flattening in the rest of expiration?

And what's causing those 0.5 spikes in IPAP at the end of each inhalation?

And is the the shape of the whole exhalation being affected by the IPAP spikes and EPAP unspikes in the transition between IPAP and EPAP?

robysue1 wrote: ↑

Mon Apr 24, 2023 9:58 pm

... the EPAP overshoots are the unspikes in red circles on the mask pressure graph. The relative IPAP bursts of 0.5 cmH2O are the spikes in the blue circles in the mask pressure graph.

Not talking about the blue circles yet. Relative IPAP (alternative term: "Psuedo-EPR")(does it sound like I'm making this stuff up as I go along?) refers to the activity between the green lines:



The blue circles are related, but occur slightly before.

The patient is on EPAP 10 cmH2O so activity outside that is extraneous. The options include:

The machine drops an extra 0.5 cmH2O (psuedo-EPR);

The machine adds an extra 0.5 cmH2O during it's expiratory phase (relative or "faux" IPAP);

The patient is doing something to generate weird stuff. In another piece of missing information, turns out this person has some restrictive lung dz. What I believe is happening is that expiration is forced because of the loss of compliance of the lung, this causes a pressure overshoot, generating a Red Herring.

Similarly, I believe the spike at end-inspiration (blue circles) is created by the forced expiration. Note that it occurs precisely at the I/E crossover point in the flow waveform (and again, it's only ~0.5 cmH2O).

Also note the green line through "Press" and 2 thin vertical black lines in the graph. These are trash but I don't feel like like redoing it cause I'm retired and can do whatever I want.

OK, black verticals showing steep expiratory curve and the pressure spike coinciding with begin expiration:

robysue1 wrote: ↑

Mon Apr 24, 2023 1:51 pm

palerider wrote: ↑

Mon Apr 24, 2023 1:29 pm

I think I really wish the zero line was turned on by default, or at least, turned on by anybody that's looking for help.

A big +1 on that comment.

I just added that to the wish list for the next version.

I tell ya, in search of "Odd Waveforms", TOF and TOOF are certainly "Target-Rich Environments":