You should read this article: Spontaneous indices are inconsistent with arterial baroreflex gain. Lipman RD, Salisbury JK, Taylor JA. Hypertension. 2003 Oct;42(4):481-7. PMID: 12975383

thank you for your input. The article from La Rovere is also relevant : "Baroreflex Sensitivity Assessment - Latest Advances and Strategies". We aware the limitations. Nevertheless, we dont have invasive measurment but only the heart rate and arterial blood pressure.

More recently we have found that spontaneous indices do not relate to neck suction derived baroreflex gain in able-bodied individuals, but do relate in those with a spinal cord injury, highlighting the confound of ongoing vascular sympathetic control of blood pressure for indexing baroreflex gain from spontaneous relations between blood pressure and heart rate. This will be presented at the annual American Autonomic Society meeting.

really intresting, thank you for sharing. do you mean that all the harware and software that claim to measured BRS with only ECG and arterial pressure are very unspecific ?

The gain of any closed loop system can usually not be estimated by simply observing presumed input/output relations. Indeed, the blood pressure input is also the output for heart rate (that regulates blood pressure via chronotropic effects on cardiac output). Better to force the system to respond - e.g., Oxford, modified Oxford, Valsalva's maneuver, neck suction. Interestingly, since they lack sufficient vascular sympathetic control, those with spinal cord injuries seem to rely on an engaged baroreflex at rest, presumably to buffer the effects of respiration etc. on blood pressure. But, one would not be able to surmise this if an open loop gain was not measured. All of those purported measurement tools from spontaneous relations rely on the broad assumption that if it looks like the baroreflex, it must be the baroreflex.

Dear Florent,

It seems like we are having to discuss the whole issue over and over: although @dr.Taylor has a point in posing the problem of measuring in a closed loop feedback system, there are some exceptions to be made. One is the fact that cardiac parasympathetic effects may act within the same beat where the systolic pressure occurs when heart rate is sufficiently low (generally below 75 bpm). The data file that you attached here has heart rates as low as 50 bpm, I would argue that this amply fulfills the condition. We have run xBRS (continuous baroreflex sensitivity) on Excel files as explained in: Wesseling, K.H et al: Validity and variability of xBRS: instantaneous cardiac baroreflex sensitivity. Physiol Rep, 5 (22), 2017, e13509, https://doi.org/10.14814/phy2.13509

Second, when looking at the data in your file I was struck by the enormous pulse pressure this 61-yr old lady seemed to have: 100 mmHg. Was this a correct measurement? Did you confirm this by comparing the NovaScope measurement to an upper arm cuff? Was she on any medication or did she have a leaky aortic valve?

Regards, John M. Karemaker