Background Apnea can be a presenting symptom in respiratory Synctial Virus (RSV) infection. The incidence of apnea in RSV infected infants varies between 16 and 25% with a particularly high risk associated with young age (< 3 mo) and prematurity. Apnea is frequently observed in early RSV infection when symptoms are still confined to the upper airways, suggesting inflammatory response induced autonomic dysfunction.

Objective The aim of the study is to assess autonomic dysfunction as indexed by Heart Rate Variability (HRV) in severe RSV infection. The secondary parameter is to analyze the effect of other viral pathogens on autonomic function in infants with LRTI requiring mechanical ventilation.

Methods Prospective observational study in a tertiary PICU in infants with viral LRTI requiring mechanical ventilation. Controls were age matched infants without signs of infection. Autonomic function was assessed via HRV, monitoring low frequency (LF) and high frequency (HF) indices of short time recordings (5 min).

Results In 7 patients and 13 controls 36 recording were analyzed. Total HRV, LF and LF/HF ratios were significant lower in RSV patients versus controls (p<0.0045, p<0.0002 and p<0.0001 respectively). In ventilated infants with LRTI caused by other respiratory viruses no significant differences in HRV versus controls were observed. These data indicate RSV related reduced sympathetic activity.

Conclusion RSV infection in infants is associated with autonomic dysfunction of central origin. This may be correlated with an increased risk for serious apnea or ALTE, for which prolonged cardio respiratory monitoring is indicated.