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

Area of Science:

• Cardiovascular Physiology
• Respiratory Physiology

Background:

• The interaction between cardiac beat-to-beat interval changes and systolic pressure (SP) variations is complex.
• Previous studies have reported conflicting findings regarding the relationship between respiratory rate and the time offset between cardiac and blood pressure changes.

Purpose of the Study:

• To assess the interaction between cardiac beat-to-beat interval changes and systolic pressure (SP) changes.
• To investigate the influence of respiration rate on the time offset between RR-interval and SP variations.
• To reconcile apparently contradictory findings in published literature by applying a standardized methodology.

Main Methods:

• Twenty subjects performed regular breathing at rates of 4, 6, 8, 10, 12, and 14 breaths per minute for 5 minutes each.
• Electrocardiogram (ECG), non-invasive blood pressure (Finapres), and respiration waveforms were recorded.
• Time offsets between cyclic patterns of RR-interval and SP changes were calculated and analyzed in relation to respiration frequency.

Main Results:

• Subjects followed displayed breathing signals effectively, with mean correlation ranging from 0.72 to 0.86.
• The time offset between RR-interval peaks and subsequent SP troughs significantly decreased with increasing respiration rate (p < 0.001).
• Applying a standardized offset definition reconciled previously conflicting data, revealing a significant relationship (p < 0.01) with a narrower prediction interval.

Conclusions:

• A significant delay exists between RR-interval changes and blood pressure variations.
• This delay is inversely related to breathing frequency.
• Standardized methodology is crucial for consistent interpretation of cardiorespiratory interactions.