Time varying heart rate variability analysis of active orthostatic and cold face tests applied both independently and simultaneously

Non-stationary heart rate variability analysis was done over a sympathetic manoeuvre, active orthostatic test (AOT) and a vagal one, cold face test (CFT), carried out either independently or simultaneously. RR interval from ECG records of 20 subjects were obtained on three conditions: AOT, CFT and simultaneous application of both stimuli (SS). HRV indexes were computed through time varying autoregressive modelling. Differences with control around intervals of interest were used for statistical comparison of manoeuvres and intervals by Friedman's test. Vagal indexes showed that CFT and SS behaved similarly (p>0.05), while sympathetic indexes indicated an AOT sympathetic predominance over SS (p<0.05) except for late recovery. An important change was observed in several indexes during early recovery for all conditions. This overshoot should be further explored.