VoluMetrix has developed a new version of its NIVAband, a wrist device that measures pressure in the veins together with the photoplethysmogram (PPG) at the same point. Previous studies have shown that the venous pressure signal (NIVA) reflected an increased HF power with respect to the electrocardiogram. This suggests that it may be useful for parasympathetic characterization guided by signal-derived respiration. Performance of NIVA signal is compared to that of PPG in a controlled breathing experiment (8 subjects) with different respiratory rates (6, 12 and 18 bpm), where a downward trend in parasympathetic estimates is expected with increasing respiratory rates. The NIVA signal is able to accurately estimate the respiratory rate (less than 0.03 Hz estimation error) in all the subjects, outperforming the PPG in the same task. In addition, respiratory-guided parasympathetic estimates significantly decreases with increased respiratory rate.