CARDIOVASCULAR AUTONOMIC REGULATION IN ASTHMATIC-CHILDREN EVIDENCED BY SPECTRAL-ANALYSIS OF HEART-RATE AND BLOOD-PRESSURE VARIABILITY

The objective of the study was to investigate the features of cardiova scular and respiratory autonomic nervous regulation in asthmatic and c ontrol children. Cardiorespiratory reactivity was studied by continuou s and non-invasive recording of the electrocardiogram, finger systolic arterial pressure (SAP) and flow-volume spirometry in supine and upri ght positions and during a deep breathing test in 19 children with bro nchial asthma and 10 healthy control children (age 8-11 years). The pe riodic variability components of R-R intervals (the time between succe ssive heart beats) and SAP in relation to respiration were assessed us ing spectral analysis techniques. Nine asthmatic children without beta (2)-agonist medication had a lower respiratory rate and larger high fr equency (HF) variability of SAP than the controls, and 10 asthmatic ch ildren with beta(2)-agonist medication had greater low-frequency (LF) variability of SAP and LF/HF ratio of R-R intervals, but their respira tory rate did not differ from the controls. No intergroup differences were found in the postural change of variables. Stable bronchial asthm a appears to increase respiratory-induced alterations in systolic bloo d pressure in children. Beta(2)-agonist medication, on the other hand, increases sympathetic cardiovascular activity in children with asthma .