Thanks for the closeup. The series of breaths you showed in closeup resemble what is usually consider flow limitation, where the inhalation rises to a peak flow, but inhale continues at a gradually declining rate until the breath is completed. This produces the flat-topped or sloping inspiratory waveform and it's not uncommon with asthma. Notice in your example, the slight pause at the end of inhale before the exhale begins, rather than a smoothly declining rate of inhale transitioning into exhale, and even a double peak at 00:36:47
RobySue, a long-time member who wrote many articles for Apneaboard posted this analysis
about another member presenting a similar waveform:
Quote:More technical information about what flow limitations look like in the wave form have been published in a number of medical journals over the years. The following chart of typical flow waves indicating flow limitations of various forms is from Chest Journal and the original paper ("Performance of Nasal Prongs in Sleep Studies: Spectrum of Flow-Related Events") is available on line at http://journal.publications.chestnet.org...id=1079501
The figure is Fig. 2 in the article.
Here's another chart of just the inspiration part of flow waves demonstrating flow limitations can be found in " Analysis of Inspiratory Flow Shapes in Patients With Partial Upper-Airway Obstruction During Sleep" also published in Chest Journal and available at http://journal.publications.chestnet.org...id=1079416
On this chart, Type 1 is the "normal" shape for an inhalation. The authors include a table titled Table 4. Characteristics and Suggested Interpretation of the Various Inspiratory Waveforms if you are interested in the authors interpretation of the other wave forms on this table.
Now to get back to jgjones1972's particular example of a breath sequence where his S9 decided to increase the pressure even though there were no OAs or Hs to be found. As jgjones1972 says, a picture is worth a thousand words. I've taken the image posted by jgjones1972 and have marked it up just a bit:
In the edited image I have circled the inhalations (the inspiratory parts) of the wave flow. Now recall that flow limitations are based on the shape of the inspiration part of the wave flow. When we compare this series of breaths to the two previous charts, we see that many of these inhalations show some of the classic "flow limitation" shapes in those inhalations. Some of the more obvious changes in shape from a normal inhalation include:
- the double peaks on the first and last circled inhalations in this set of data.
- the sharp triangular "peak" followed by an almost linear decrease that is present in almost all of the circled inhalations as opposed to a more "rounded" normal inhalation.
- a "chair" pattern that is subtly present in circled breaths #2, 4, 5, and 12 (especially 12) where there is a (very) short plateau during the inhalation before the large, normal exhale dip starts.
This series of breaths is clearly demonstrating enough characteristics of "flow limitations" that an S9 AutoSet or a PR System One Auto would definitely be increasing the pressure during this time---if the pressure is not already at max pressure. And sure enough, if we look very closely at the pressure curve, we can see the beginning of the pressure increase about halfway between 04:02:40 and 04:02:50.
As you can see, the flattened top of the inspiratory curve under flow limitation looks familiar, compared to the example you posted. This 2013 post could easily be an analysis of the waveform you submitted. If you were using an AutoCPAP, I would expect the pressure to increase until that flow limitation is reduced or eliminated. Your CPAP does not analyze flow limitation in its current mode. I would suggest changing your machine to Auto mode, and set the minimum and maximum pressure at 10. This will make it work as a CPAP, but it will flag flow limitation.
This pattern might also be an argument in favor of bilevel for you, if flow limitation is confirmed, because you would have higher inspiration pressure to overcome this flow limitation, and expiration pressure relief to ensure a more natural respiratory cycle. In your case, the tidal volume and minute vent shows poor efficiency with this flow limitation as well, dropping to very low levels during this period you posted. These would be improved a lot with bilevel. So your idea of perhaps checking oximetry may not have been a bad one, in light of the extent of flow limitation suggested in your post, but not reflected by considering the "event count".
That's my non-professional take. Maybe it's worth a discussion with your doc. It will be interesting to see what some other members think about this as well.