Reproducibility of a non-invasive real-time measure of cardiac parasympathetic activity

The NeuroScope is a new device which produces a continuous real-time index of cardiac parasympathetic activity (the CIPA) and accurately measures RR i ntervals. The reproducibility of the CIPA has not yet been assessed. This s tudy was designed to assess the reproducibility of a 5 minute recording of the CIPA using the NeuroScope and compare it with that of conventional hear t rate variability (HRV) measures. 50 subjects (31 male, 19 female) aged 21-77 years were recruited. I I of th ese were apparently healthy and 39 were patients with a variety of cardiolo gical problems. Two 5 minute recordings of CIPA and RR intervals for each s ubject were made with a 2-3 minute break between recordings. The limits of agreement for the CIPA were such that the second estimate was between 72 an d 140% of the first estimate, 95% of the time. The limits of agreement for other indices of HRV, namely SDNN, rMSSD, In low-frequency HRV and In high- frequency HRV, were 61-157%, 68-153%, 77-131% and 76-133%. The short-term reproducibility of a 5 minute recording of CIPA is moderate and better than simple time-domain but not frequency-domain measures of HRV .