CARDIOVASCULAR PERIODICITIES IN HEALTHY HUMANS IN THE ABSENCE OF BREATHING AND UNDER REDUCED CHEMICAL DRIVE OF RESPIRATION

In 20 healthy human subjects (aged 20-24 years) power density spectra in 1-min time series were computed by modified MATLAB procedures from inter-beat heart intervals and systolic and diastolic finger blood pre ssure. High- (HF), mid- (MF) and low-frequency (LF) peaks (0.16-0.37 H z, 0.08-0.12 Hz and 0.02-0.05 Hz, respectively) were distinguished in power density spectra (PDS). During 1-min voluntary apneas MF and LF p ower increased and in 18 out of 20 subjects HF peaks disappeared in PD S. Breath holding performed in hyperoxia or in hyperoxia accompanied b y 1-min hyperventilation preceding apnea augmented power at MF and LF range and abolished marginal HF peaks present in the spectrum in two s ubjects. It is concluded that apneic PDS is characterized by augmented power of MF and LF rhythms, and represents endogenous free running ca rdiovascular periodicities released from feed-back mechanical, reflex and feed-forward central entrainment to respiratory rhythm.