[split] Respironics flow limitation info

[Walla Walla]

Since the talk about Resmed and dreamstations I have one problem with the Dreamstation when using it. I don't know what a flow limitation event on the Dreamstation is.

On the Resmed it's on a graph and you can see exactly whats going on. I'd like to know how much of a limitation it takes to trigger a limitation event on the Dreamstation.

20%, 30% ? Anyone know the answer to this?

[Shin Ryoku]

I don't have a direct answer to your question, but I'd question how straightforward it really is to "see exactly what is going on" in the ResMed flow limitation graph you mentioned.

This is a recent review: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4629962/

In order to evaluate flow limitations, Respironics determines roundness, flatness, skewness, and WPF to rate the most recent four breaths as better, worse, or the same compared to baseline. Roundness is determined by the similarity of the WPF between 5% and 95% values to a sine wave. Flatness is determined by the absolute value of the variance between 20% and 80% of inspiratory flow from the average of all the values in the same period, divided by 80% volume point. Skewness is determined by dividing the average of the highest 5% of flows in the mid third of the breath by the average of the highest 5% of flows in the first third of the breath.

What combination of all that is counted as an "event" is not clear. I don't know if they've specified publicly anywhere.

ResMed also determines flow limitation. S8 AutoSet defines flow limitation using flatness of an inspiratory breath. The flatness index is calculated by the RMS deviation from unit scaled flow calculated over the middle 50% of a normalized inspiratory breath.4 From the S9 onward, flow limitation is calculated using a combination of flatness index, breath shape index, ventilation change, and breath duty cycle. Ventilation change is the ratio of the current breath ventilation to recent 3-minute ventilation. Breath duty cycle is the ratio of current breath time of inspiration to total breath time of recent 5 minutes. If a breath is severely flow limited, the flow limitation index will be closer to one and when the breath is normal or round, the flow limitation index will be zero.

So when I look at my S10 Autoset download and see a bar for "0.33 flow limitation", what combination of flatness index, breath shape index, ventilatory change, and breath duty cycle computes to 0.33? It's not as if they are saying it means a 33% reduction in flow or some direct translation like that.

[Walla Walla]

That was quite a way of saying I don't know. I guess that's the Doctor in you.

Being the dummy I am I like to see the graph and where the machine reacts to it. It may not be exact but it does give me something to gauge by.

The Dreamstation gives me nothing to compare the FL event to before or after. Thus the question of what it is.

[Shin Ryoku]

I like to see the graph and where the machine reacts to it. It may not be exact but it does give me something to gauge by.

The Dreamstation gives me nothing to compare the FL event to before or after. Thus the question of what it is.

I like how easy it is to see the event flags for flow limit on the DreamStation. If I want to see a visual representation of what is being reacted to, I look at the flow rate tracings.

[Walla Walla]

Shin,
I'm not debating you about what you like about the Dreamstation. I'm just trying to find an answer to my question.

[Shin Ryoku]

deleted, waste of time