Characterization of Whole Body Vibration Exposures in Neonatal Ground Transport

Abstract

Newborn infants delivered in a compromised health state often require transport between secondary and primary care hospitals. The objective of this study was to measure and characterize Whole Body Vibration (WBV) exposures during simulated newborn infant inter-hospital ground transport and determine how vehicle-based vibration is transmitted through the chain of equipment used to support newborn infants and whether there is a need and potential for mitigation of these exposures. These WBV exposures were also compared to two typical daily activities of infants, riding in a car seat and riding in a stroller. A simulated newborn infant was transported over a typical transport route utilizing a standard stretcher system and two potentially mitigating strategies: a modified stretcher system with a stabilizing strut and a new, modified vibration dampening stretcher system. The average-weighted vibrations and the vibration dose values were calculated, and the frequency spectra profiles were examined. Relative to the floor measured vibration (0.36 m/s2), the standard stretcher system amplified the average weighted vibration through the chain of equipment nearly doubling the vibration at the interface where the simulated neonate rested (0.67 m/s2). These measures exceeded those found with the car seat and the indoor stroller. The new stretcher system with the built-in suspension reduced the exposure at the interface to 0.48 m/s2. In contrast, the strut-based stretcher system did not perform as expected, increasing the vibration at the interface (1.2 m/s2). Results were similar for VDV exposures. The frequency spectra present in the standard stretcher system was primarily between 4-15 Hz, raising concern because of the overlap with natural resonance frequency of the human body (4-12 Hz). The new stretcher with the built-in suspension effectively negated the vibrations in the 4-10 Hz range. The transmissibilities indicated that there is potential for further mitigation at points between the aluminum transfer sled and the interface. This research presents a unique mitigating strategy to reduce elevated neonate whole body vibration exposures and addresses potential further mitigation points. It also contributes information to the field for further development of standards and implementation of whole body vibration exposure limits that are applicable across the lifespan.