Evaluation of autonomic modulation of lung function and heart rate in children with cystic fibrosis.

The autonomic nervous system (ANS) plays an important role in modulating bronchial smooth muscle contractility, which is altered in cystic fibrosis (CF). A convenient approach to probe ANS regulation is the quantitative analysis of heart rate variability (HRV). The purpose of this study was to evaluate ANS regulation in children with CF and to investigate the influence of colonization by Pseudonomas aeruginosa via assessment of HRV in colonized CF (CCF) children and noncolonized CF (NCCF) children. Sixteen children with CF (7 CCF and 9 NCCF) and seven healthy age-matched control children were enrolled in the study. Heart rate was recorded for 10 min at rest in the supine and standing positions and HRV analysis was carried out using autoregressive spectral analysis. The CCF group was characterized by lower forced expiratory volume than NCCF, indicating an impairment of respiratory function. The HRV parameters further confirmed the possible sympathetic overactivity in CCF. Children with CF exhibited hyperactivity of the sympathetic nervous system. In particular, the CCF group presented a greater impairment of ANS modulation. Both CCF and NCCF children showed lower supine vagal activation in the HRV indices related to sympathetic activation and reduction of indices indicating vagal activity with the postural change from supine to standing when compared to the NCCF group.