ABSTRACT 528

Abstract

Background and aims: During mechanical ventilation, arterial pressure variations, like the pulse pressure variation (PPV), can be observed in neonates. However, in clinical practice it is observed that the frequency of this observed PPV does not always correspond with the respiratory rate. It is hypothesized that PPV in neonates is indeed caused by cardiopulmonary interaction, but that this mismatch is caused by the low heart rate/respiratory rate (HR/RR) ratio seen in neonates. Aims: The goal of this study is to investigate the relation between PPV and ventilation in neonates. Methods: Continuous monitoring of the arterial blood pressure and respiratory signal (capnograph or thoracic impedance) was performed in 20 neonates on synchronized intermittent mandatory ventilation (SIMV) and 10 neonates on high frequency ventilation (HFV). The hospital ethics committee waived the need for informed consent. To investigate if the mismatch is caused by the low HR/RR ratio, the value of the respiratory signal was taken at the moment of a heartbeat (RespHR) (since the effect of ventilation on circulation is only expressed per heartbeat). To determine if the observed PPV is caused by cardiopulmonary interaction, the correlation between RespHR- and PP was determined. Results: The frequencies observed in PP, not corresponding to the respiratory rate, were also observed in RespHR. The correlation between RespHR and PP was -0.64 ± 0.18 and 0.55 ± 0.16 for SIMV and HFV, respectively. Conclusions: The arterial pressure variations observed in neonates on SIMV or HFV are indicative for cardiopulmonary interaction and the observed mismatch is caused by the low HR/RR ratio.