Sir Banned- Would you mind getting your message board login working? A guest login somehow isn't befitting someone with your heartwarming message board history.
Mr Capers- your rise time is currently set to either 2 or 3... right?
According to the provider manual, there is only one parameter called "inspiratory time" and another interrelated parameter called "rise time"---with that "rise time" depicted simply as a lesser portion of "inspiratory time". There is no third additive parameter that Respironics calls "total inspiration time". Nor do the waveform diagrams represent a third additive parameter.Sir Banned wrote:(Remember Inspiration Time and Rise Time are additive for Total Inspiration time).
And, in fact, they mention one caveat of selecting a long rise time is that it may deplete too large a portion of the set inspiratory time---making for very little time spent at targeted IPAP peak.
A blast from the past relating to I time considerations with respect to overall BPM:
viewtopic.php?f=1&t=35298&p=304575&#p304575
two general characteristics of inspiration time have to do with either achieving a certain tidal volume, a certain I:E ratio, or both.
In certain cases of COPD, for instance, clinicians might try to achieve more expiratory time by influencing the I:E ratio. To accomplish that they need to factor BPM and IT together. BPM yields the total time spent in I + E. Of that total time spent in I + E, a set inspiratory time (IT) will drive the ratio of how much time is spent in each. The IT setting will specifically account for time spent in inspiration; and almost all of the remaining time will be allotted for expiration (there are also slight intervening pauses between respiratory phases only slightly contributing toward that total remaining respiratory time).
Alternately, IT can be used to help with central dysregulation since IT directly helps regulate the amount of inspired O2---while indirectly regulating the rate of expired CO2 (via expiratory time implicitly defaulted or remaining by employing the IT and BPM parameters). A shorter IT or inspiratory time period amounts to less O2 volume inspired, which can supposedly help with periodic breathing. Again, if IT is employed toward I:E ratio-adjustment (by also utilizing the BPM parameter), a clinician can even influence CO2 expiration rates via the time allotted for the expiratory phase relative to inspired volume. However, that's not the same as directly influencing CO2 retention via additional appropriate methods.
So when the autoSV titration guide says "Set Fixed Rate to a minimum of 10 BPM... Start I time: 1.2 seconds" we can at least see how those 10 BPM and 1.2 second IT parameters play against each other ratio-wise: here the I:E ratio would be 1.2 sec to 4.8 sec (which can be numerically reduced to an I:E ratio of 1:4). However, that "minimum of 10 BPM" recommendation tells us that the starting ratio might favor a somewhat smaller E number. Regardless, if we compare that against a default setting of 1:1 or say an acceptable spontaneous 1:2 ratio, we can see that Respironcics implies that central apneas can be countered, at least in part, with comparatively shorter inspiratory volumes and times.
However, also bear in mind that the AutoSV's BPM setting is only a backup setting, and that faster spontaneous breathing rates by the patient will diminish time spent in E while still holding the above 1.2 second inspiratory time constant. Recall that BPM is typically set at the patient's spontaneous rate minus 2. Here setting BPM rate much closer to a machine-affected or influenced spontaneous rate can allow the clinician to additionally impose tighter control over time spent in E. Allowing for BPM as a non-salient backup rate (as opposed to either tightly enforced or purely timed mode scenarios), the above spontaneous I:E ratios can thus be more accurately estimated during periods that are free of central dysregulation by also including that BPM offset of 2 into the above ratio calculations. Easier yet: just calculate that I:E scenario of a non-salient backup rate using the patient's measured spontaneous BPM, rather than employing machine backup rate along with spontaneous offset.
