THE ACUTE EFFECTS OF INHALED SALBUTAMOL ON THE BEAT-TO-BEAT VARIABILITY OF HEART-RATE AND BLOOD-PRESSURE ASSESSED BY SPECTRAL-ANALYSIS

Aims We wanted to study the effects of a 600 mu g inhaled salbutamol d ose on the cardiovascular and respiratory autonomic nervous regulation in eight children suffering h-om bronchial asthma. Methods In this ra ndomized, double-blind, placebo-controlled, crossover study we continu ously measured electrocardiogram, finger systolic arterial pressure (S AP) and flow-volume spirometry at baseline as well as 20 min and 2 h a fter the drug inhalation. The R-R interval (the time between successiv e heart beats) and SAP variabilities were assessed by using spectral a nalysis. Baroreflex sensitivity was assessed by using cross-spectral a nalysis. Results Salbutamol significantly decreased the total and low frequency (LF) variability of R-R intervals as well as the high freque ncy (HF) variability of R-R intervals and of SAP. Salbutamol significa ntly increased the LF/HF ratio of R-R intervals and of SAP, minute ven tilation, heart rate and forced pulmonary function in comparison with placebo. The weight of the subjects significantly correlated positivel y with baroreflex sensitivity and negatively with heart rate after the salbutamol inhalation. Conclusions We conclude that the acute salbuta mol inhalation decreases cardiovagal nervous responsiveness, increases sympathetic dominance in the cardiovascular autonomic balance, and ha s a tendency to decrease baroreflex sensitivity in addition to improve d pulmonary function.