Acceleration during neonatal transport and its impact on mechanical ventilation.

OBJECTIVE

During interhospital transfer, critically ill neonates frequently require mechanical ventilation and are exposed to physical forces related to movement of the ambulance. In an observational study, we investigated acceleration during emergency transfers and if they result from changes in ambulance speed and direction or from vibration due to road conditions. We also studied how these forces impact on performance of the fabian+nCPAP evolution neonatal ventilator and on patient-ventilator interactions.

METHODS

We downloaded ventilator parameters at 125 Hz and acceleration data at 100 Hz sampling rates, respectively, during the emergency transfer of 109 infants. Study subjects included term, preterm and extremely preterm infants. We computationally analysed the magnitude, direction and frequency of ambulance acceleration. We also analysed maintenance and variability of ventilator parameters and the shape of pressure-volume loops.

RESULTS

While acceleration was <1 m/s most of the time, most babies were occasionally exposed to accelerations>5 m/s. Vibration was responsible for most of the acceleration, rather than speed change or vehicle turning. There was no significant difference between periods of high or low vibration in ventilation parameters, their variability and how well targeted parameters were kept close to their target. Speed change or vehicle turning did not affect ventilator parameters or performance. However, during periods of intense vibration, pressure-volume ventilator loops became significantly more irregular.

CONCLUSIONS

Infants are exposed to significant acceleration and vibration during emergency transport. While these forces do not interfere with overall maintenance of ventilator parameters, they make the pressure-volume loops more irregular.