RSA

Posts: 3
Joined: 11 Oct 2012, 17:13

RSA

Postby Sophie Reijman » 17 Oct 2012, 10:57

Hi, in our study we look at physiological reactivity to infant stimuli in adults. We are measuring heart rate, skin conductance levels, and we also want to look at heart rate variability. Infant stimuli are presented in segments of 10 seconds each, so for all physiological measures the average per segment of 10 seconds is calculated, and we are looking at increases and decreases in these averages as the stimuli accumulate.
Since in our VU-AMS output we have a lot of missings on RSA, we have so far used RMSSD. Could you tell us what exactly is the difference between RSA and RMSSD in using either as measure of HRV? Are there (important) disadvantages to using RMSSD? Is there something else you would recommend / we should take into account?

Thanks in advance,
Sophie

Posts: 9
Joined: 20 Jan 2012, 21:03

Re: RSA

Postby jcndegeus » 17 Oct 2012, 12:28

Hi Sophie,

RSA is calculated by subtracting the shortest IBI during an inspiration from the longest IBI during expiration. It is the theoretically most sound measure of cardica vagal control. Empirically it correlates very highly with RMSSD, so the former can be used as well.

I am not sure why RSA is missing so often from your 10 second averages. Have you looked at the Respiratioon Scoring Tab to see what is going on?

Cheers,

Eco

Posts: 1
Joined: 13 Sep 2013, 06:01

Re: RSA

Postby ndc_user » 10 Feb 2014, 11:07

Hi VU-AMS Team,

At the moment, we are using your device to assess RSA. Can I clarify if there is a minimum period in order to obtain a reliable RSA value? I read that there is a recommendation of 4 minutes; however, I note that RSA can be calculated by the subtraction of shortest and longest IBI in a breathing cycle (which is very short compared to 4 minutes) , and have also noticed that the programme generates a RSA value even for 5s period. Can I take the given RSA value generated by the programme as a reliable measure for any time period I intend to extract the data from?

Thanks.

Posts: 9
Joined: 20 Jan 2012, 21:03

Re: RSA

Postby jcndegeus » 10 Feb 2014, 15:36

Hi Sophie,

There are 3 different measures generated by the VU-AMS that are all use dto index the RSA phenomenon
- pvRSA = peak valley RSA which is computed on a breath to breath basis and most closely corresponds to what 'respiratory sinus arrhythmia' actually means.
- RMSSD = root means square of succesive differences which is only dependent on the IBI time series and would be less sensitive to bad respiration scoring from the dZ. It is empirically closely related to pvRSA although theoretically somewhat less directly connected to the RSA phenomenon

Both RMSSD and RSA can be computed on fragments of 10 to 15 seconds, although reproducibility of individual differences will of course increase if you average across longer periods.

- HF = High Frequency power of the IBI time series (0.15 -0.4 Hz). For this the VU-AMS indeed requires at least 4 minute periods of recording.
HF is highly correlated to both RMSSD and pvRSA.

RMSSD and HF are the measures most often used in cardiological literature; pvRSA is most often encounterd in the psychophysiological field.

Best,

Eco

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