jsthomps,(time=1277734681) Wrote:I have using ResScan for a month now and the data is very interesting. Some data is self-evident but I don't understand a lot of it. Perhaps someone can shed light on the following:
Hi Scott and welcome to Apnea Board!
I'm not a Sleep Technician, but I'll do my best to answer based upon what I've learned in various places on the Internet. Maybe others with more experience can add to this, but here's what I've learned:
AHI and AI (events/hr)
AHI is Apnea/Hypopnea Index; AI is Apnea Index; HI is Hypopnea Index. AI + HI = AHI, so AHI is the combined number of Apnea and Hypopnea events per hour. An Apnea event is a cessation of breathing for 10 or more seconds during sleep while a Hypopnea is an episode of diminished breathing during sleep, caused by a partial airway obstruction, and resulting in arousal. Usually accompanied by oxygen desaturation. Hypopneas may be just as serious as apneas and have the same troublesome effects.
Apnea or hypopnea events (sec) Aperiodic
"Aperiodic" means "occurring without periodicity" or "irregular", but as I'm not a sleep technician, I really don't understand what this is, or the significance of it. Maybe someone else can help here.
Flow limitation (flat to round)
A Flow Limitation is a partial closure of the upper airway, which impedes the flow of air into the lungs. According to ResMed, this is one of the 3 main parameters they use in determining effective auto-titration. The 3 parameters are flow limitation, snore, and apnea.
What does "flat to round" mean?
This has to do with how the graph "looks". Basically, when using a mathematical representation of the shape of the breath (flow time curve) to indicate the state of the upper airway, a "round" shape denotes an open patent airway while a "flattened" shape indicates a flow limited airway. So, flat is bad, round is good.
Flow (L/min)
Flow is an estimate of the airflow entering the lungs.It is derived by taking the total flow and then removing the leak and mask vent flow components.
Leak (L/sec)
Leak is an estimate of the total rate of air escaping due to mouth and mask leaks. It is derived by analyzing the inspiratory and expiratory airflows, together with the expected mask vent flows. High or changing leak rates may affect the accuracy of other measurements.
Minute ventilation (L/min)
Minute Ventilation is the volume of air breathed in (or out) within any 60 second period.
Snore (quiet to loud)
Snore or "Snore Index" is the measure of the amplitude of pressure wave generated by a patient's snoring
How is snore volume measured (microphone)?
There is a secret microphone that records your snoring and sends it to ResMed, and thanks to Homeland Security and the Patriot Act, also records your private bedtime talk and sends that to the National Security Agency for real-time terrorist analysis...
Okay, not really.
There is no microphone. It is an estimate of the loudness of your snoring based upon the amplitude of the pressure wave of the snore - pressure is measured to get this reading, not sound waves.
Here are ResMed's definitions of some of the various terms used in ResScan:
Compliance
Usage = the time that a patient receives therapy from the device.
Used Days > X hours Y minutes = the total number of days where Daily Usage exceeded the compliance threshold (X hours Y minutes).
% Used Days > X hours Y minutes = % Used Days calculates the percentage of Used Days out of the total number of days selected.
Total Hours Used = the total patient Usage over a selected time range.
Events
Apnea = the temporary absence or cessation of breathing. An apnea is scored when there is reduction in breathing by 75% of the baseline breathing for at least 10 seconds.
Obstructive Apnea = when there is a physical closing of the upper airway. Central Apnea = when the upper airway remains open.
Unknown Apnea = when accurate determination of whether the apnea is obstructive or central is not possible, due to the leak at any time during the apnea being higher than 30 L/min.
Hypopnea = episode of shallow or slow breathing during sleep. A hypopnea is scored when there is a reduction in breathing by 50% of baseline breathing for 10 seconds or more. The event is scored after 10 seconds of the hypopnea.
AHI = Apnea-Hypopnea Index (AHI) = calculated by adding together the total number of apnea and hypopnea events over a period of time. For statistics, it is the total number of events divided by total Daily Usage. For graphs, the AHI count is incremented at the occurrence of every event and reset every hour.
Key Respiratory Parameters
Leak = an estimate of the total rate of air escaping due to mouth and mask leaks. It is derived by analyzing the inspiratory and expiratory airflows, together with the expected mask vent flows. High or changing leak rates may affect the accuracy of other measurements.
Tidal Volume = the volume of air inspired or expired in one respiratory cycle (breath).
Respiratory Rate = the frequency of breathing, expressed as the number of breaths per minute.
Minute Ventilation = the volume of air breathed in (or out) within any 60 second period.
Flattening = a measurement of partial upper airway obstruction. This measurement is based on the shape of the inspiratory flow-time curve. A flat shape suggests upper airway obstruction.
Snore index = the measure of the amplitude of pressure wave generated by a patient's snoring.
% Spontaneous Triggered Breaths = the percentage of patient breaths that were spontaneously triggered (initiation of IPAP).
% Spontaneous Cycled Breaths = the percentage of patient breaths that were spontaneously cycled (termination of IPAP and changing to EPAP).
Oxygen Desaturation Index = the mean value of the number of drops in oxygen saturation per hour. Flow = an estimate of the airflow entering the lungs.It is derived by taking the total flow and then removing the leak and mask vent flow components.
Flow Limitation = a measurement of partial upper airway obstruction.
Statistics
95th Percentile = the value exceeded during the selected range for 5% of the time.
Median = the median value recorded during the selected range.
Maximum = the maximum value recorded during the selected range.
