Heart rate changes during positive pressure ventilation after asphyxia-induced bradycardia in a porcine model of neonatal resuscitation.

Abstract

BACKGROUND: The Neonatal Resuscitation Program (NRP) states that if adequate positive pressure ventilation (PPV) was given for a low heart rate (HR), the infant's HR should increase within the first 15 s of PPV. OBJECTIVE: To assess changes in HR in piglets with asphyxia-induced bradycardia. METHODS: Term newborn piglets (n=30) were anaesthetised, intubated, instrumented and exposed to 50 min normocapnic hypoxia followed by asphyxia. Asphyxia was achieved by clamping the tube until severe bradycardia (defined as HR at25% of baseline). This was followed by 30 s adequate PPV and chest compression thereafter. Changes in HR during the 30 s of PPV were assessed and divided into four epochs (0-10 s, 5-15 s, 10-20 s and 20-30 s, respectively). RESULTS: Increase in HR >100/min was observed in 6/30 (20%) after 30 s of PPV. Within the epochs 0-10 s, 5-15 s or 10-20 s no piglet had an increase in HR >100/min. Additional 10/30 (33%) had a >10% increase in HR. CONCLUSION: In contrast to NRP recommendation, adequate PPV does not increase HR within 15 s after ventilation in piglets with asphyxia-induced bradycardia.