O3316: Decreasing the Incidence of Intraventricular Hemorrhage in Neonatal Populations by Mitigating the Vibrations and Noise Levels Experienced During Transport

Background: Premature infants are faced with a greater risk of intraventricular hemorrhage (IVH) due to underdeveloped blood vessels. While ground ambulance transportation is necessary when specialized neonatal care is unavailable at the neonate's birth facility, transport exacerbates the risk of IVH due to intense vibration and noise exposure. Reducing vibration and noise within the isolette and stretcher during transportation may help lower the incidence of IVH.

Methods: We have documented the mechanical vibration and sound exposure experienced by a 24-week, 0.59-kg, neonatal manikin during ground transport in a Type 1 ambulance provided by Cincinnati Children’s Hospital and Medical Center. We used 14 triaxial accelerometers and two International Organization for Standardization (ISO) 1996-2:2007 certified, Optimus Sound Level Meters. The accelerometers were placed on the manikin, isolette, and throughout the interior of the ambulance (Fig. 1A). The sensor on the manikin was placed its forehead (Fig. 1B). One noise meter was placed inside the isolette, while the other was placed on top of the isolette (Fig. 1D). The ambulance drove for 25 minutes with a mix of highway and city miles and briefly activated the siren to simulate authentic transport scenarios. The mechanical vibrations were compared to the ISO 2631 acceleration comfort scale for mechanical vibration and shock, which is intended to be used for adults since there are no standards for infants and children. The A-weighted decibels (dBA) were compared to the American Academy of Pediatrics’ (AAP’s) recommendations for noise exposure ( < 45 dBA).

Results: Our results indicate that the manikin experienced forces exceeding the recommended “comfortable” 0.032 g limit for the entire duration of the simulated transport event (Fig. 1E-1G). Even more alarming, the manikin experienced higher forces than the ambulance, suggesting the rigid mechanical coupling of the isolette-cot system to the ambulance provides no shock absorption, but instead induces resonance, increasing the magnitude of the acceleration experienced by the manikin. The average noise level inside the isolette was 63.4 dBA, which is 18.4 dBA higher than the level recommended by the AAP. From preliminary experiments to reduce the vibrations and noise levels, we found that an enclosure made of 0.125-inch plexiglass could reduce sound levels by >30 dBA. We also found that a gel-infused memory foam placed between the isolette, and the stretcher could reduce peak accelerations by 30% during benchtop experiments.

Conclusion: Our findings highlight both excessive mechanical vibration and noise levels experienced by neonates during ground ambulance transportation, which both exceed recommended safety and comfort thresholds. The rigid coupling of the isolette and stretcher can amplify these forces, offering no shock absorption to protect the neonate. Early experiments suggest that additional vibration dampening and soundproofing material could help reduce the mechanical vibration and noise levels experienced during transport.