Interaction between cardiac beat-to-beat interval changes and systolic blood pressure changes

Abstract.  This study assessed the interaction between cardiacbeat-to-beat interval changes and systolic pressure (SP)changes. Twenty subjects breathed regularly following displayedbreathing signals at 4, 6, 8, 10, 12 and 14 breaths per minute,each for 5 minutes. ECG, non-invasive blood pressure (Finapres)and respiration waveforms were recorded. Time offsets betweenthe cyclic patterns of RR-interval and SP changes werecalculated. Displayed breathing signals were well followed; themean correlation between displayed and recorded breathingsignals ranged from 0.72 to 0.86. The time offset betweenRR-interval peaks and subsequent SP troughs decreased withincreasing respiration rate, 3.8 ± 1.7 s, 3.5 ± 0.7 s, 3.1 ± 0.6s, 2.6 ± 0.4 s, 2.3 ± 0.4 s and 2.0 ± 0.4 s mean ± SD at 4, 6,8, 10, 12 and 14 breaths per minute respectively. Therelationship between mean time offset and frequency wassignificant (p < 0.001), with a 95% prediction interval of ±0.24 s. Published data showed no relationship between timeoffset and frequency, with a 95% prediction interval of ± 2.8 s.However, when the offset definition proposed in this researchwas applied to these data, a significant relationship (p <0.01) was evident, with a 95% prediction interval of ± 1.5 s. Inconclusion, apparently contradictory previous findings achievegood consensus when a standardized method for presenting resultsis applied. A delay exists between RR-interval and bloodpressure changes, and this delay varies with breathingfrequency.