understanding inspiration time, expiration time and respiration rate

My OSCAR details of my DS1 autopap provide a trace of inspiration and expiration times in seconds. I am presuming that the inspiration time is measured by the time period from the flowrate changing from negative to returning to negative. Visually: and conversely the expiration time is measured by that period of time that the flowrate is in the negative.

Is my understanding correct?

Now, is the respiration rate (Breaths/min) an actual measure of the number of breaths taken in the past 60 seconds, or is it the extrapolation of current breath (sum of inspiration and expiration) time, expressed as rate?

I found this site to be very helpful with all things OSCAR.

http://www.apneaboard.com/wiki/index.p ... Rate_graph

I second the above comment. The site referenced is excellent, as are the other parts of the Apnea Board wiki. This does require some effort on your part but you come away understanding.

CyberSpiff wrote: ↑

Sun Oct 31, 2021 12:51 pm

That certainly did help, and perhaps the important thing I learned right off was that these devices do not directly measure flow, rather the devices derive from from pressure readings. (This seems to be in contradiction with the assertion that Resmed and Respironics machines (for "home" use) have flow meters.

The majority of the discussion on this page addresses events and their evaluation. But it did not address my question about respiration rate. So, in addition to my original question of the basis of the rate calculation I've realized that an additional factor needs to be understood. Below is an example of "normal" breathing morphology:


and here is an actual example of my "normal" breathing:
So one of my question about respiration rate (if were to be measured on a breath-by-breath) basis would be: Is the time for complete breath measured by "A" or "B" ?
As an alternative, I also seems to me that the instantaneous (breath-by-breath) rate determination is probably not very useful, but a running rate (say over the previous 10-15 seconds) would have more value.

I'm of the impression that the inspiration phase of breathing is an active action, in that muscles are actively employed to left the chest wall and contract the diaphram. On the other hand, the expiration phase is passive, the chest wall is allowed to collapse or rest and the diaphram returns to it's resting state. A time pause between the expiration and subsequent inspiration can be thought of as waiting for the next signal to activate the chest and contract the diaphram (absent any obstruction in the airway).

Absent any obstruction, chronically long pauses between expiration and inspiration is a neurological problem.

Do I have most of this right?

From what I've read here (I'm fairly new to this - about two months on CPAP), the most useful data is on the first three graphs (Events, Flow Rate and Pressure). Total Volume and Leak Rate are only relevant if leaks are flagged as an issue. I have a Devilbiss (Intellipap in the US) machine which also picks up Exhale or Expiratory Puffs (most machines either ignore these or record them as leaks far as I know). From analysing my own Flow Rate graphs and flagged "exhale puff" events, your breathing pattern looks a bit similar, i.e. with part of the exhale breath just shown as a flat line. This can't happen if your mask covers both your nose and mouth (I just have a nasal pillow). So you may be having periods where you are breathing in through your nose but partially out through your mouth (if you have a mask which leaves your mouth exposed). Have you scanned through a full night of flow rate data to see what percentage of time your pattern is like this? If it's like that all the time, might indicate some leakage. I suggest you show some screen shots here from Oscar and let some of the experts chip in. My tuppence worth is just familiarity with the exhale puff pattern from personal experience.

Regards exhale puffing (breathing out through the mouth), the advice I've had from my technician is that it's only an issue if accompanied by flow restriction events (apneas and hypopneas). The problem is that exhale puffing disguises things like snoring, so the CPAP machine may not respond quickly enough (increased pressure) to prevent onset of restrictive breathing events. If these don't happen, then the exhale puffing is not really an issue. I'm no expert, but my technician knows his stuff, so I'm inclined to trust him on this. Hopefully, of some help to you. BTW, a quick word of advice based on personal experience. I have an engineering background (I suspect you may have too). It's all too easy to get sucked into the technicalities of all this and forget that the main objective is to get a good night's sleep, while significantly reducing the number of apneas and hypopneas. Don't lose sight of the former! For example, I didn't have a particularly good night's sleep last night (dinner too late I think). But my events were very low, mainly because I had a lot of shallow sleep and periods when I was either fully or almost awake. The previous night I slept really well but my flagged events were much higher (but still under 5 per hour).

MMcG wrote: ↑

Mon Nov 01, 2021 4:59 am

your breathing pattern looks a bit similar [to my own] , i.e. with part of the exhale breath just shown as a flat line. This can't happen if your mask covers both your nose and mouth

I am using a full face mask, so both mouth and nose flows are captured
BTW, I am sending you a private message