Neonatal head and torso vibration exposure during inter-hospital transfer

Abstract

Inter-hospital transport of premature infants is increasingly common, given the centralisation of neonatal intensive care. However, it is known to be associated with anomalously increased morbidity, most notably brain injury, and with increased mortality from multifactorial causes. Surprisingly, there have been relatively few previous studies investigating the levels of mechanical shock and vibration hazard present during this vehicular transport pathway. Using a custom inertial datalogger, and analysis software, we quantify vibration and linear head acceleration. Mounting multiple inertial sensing units on the forehead and torso of neonatal patients and a preterm manikin, and on the chassis of transport incubators over the duration of inter-site transfers, we find that the resonant frequency of the mattress and harness system currently used to secure neonates inside incubators is ~9Hz. This couples to vehicle chassis vibration, increasing vibration exposure to the neonate. The vibration exposure per journey (A(8) using the ISO 2631 standard) was at least 20% of the action point value of current European Union regulations over all 12 neonatal transports studied, reaching 70% in two cases. Direct injury risk from linear head acceleration (HIC15) was negligible. Although the overall hazard was similar, vibration isolation differed substantially between sponge and air mattresses, with a manikin. Using a Global Positioning System datalogger alongside inertial sensors, vibration increased with vehicle speed only above 60 km/h. These preliminary findings suggest there is scope to engineer better systems for transferring sick infants, thus potentially improving their outcomes.

Association of early postnatal transfer and birth outside a tertiary hospital with mortality and severe brain injury in extremely preterm infants: observational cohort study with propensity score matching

“…The rate of severe brain injury was not significantly higher in non-transferred infants who remained in non-tertiary neonatal hospitals compared with controls. This finding has two possible explanations: these infants might have died before severe brain injury was detected, as mortality was higher in this group, or there may be a mechanistic link between early postnatal transfer and brain injury related to physiological instability or vibration injury during transport 51…”

Neurocritical care of high‐risk infants during inter‐hospital transport

“…During neonatal transport, WBV often exceeds the recommended level deemed safe for adults with the head of the infant appearing to be at greatest risk . Excessive exposure in adults can cause ill effects including musculoskeletal and neurovascular injury .…”

“…Vibration and linear acceleration experienced during the transfer process may lead to fluctuations in CBF and be the key mechanism for IVH in preterm infants and although causation is challenging to demonstrate it is supported by animal models . Attempts to reduce WBV exposure with the use of different mattresses, including gel materials, have not demonstrated effective attenuation of WBV, especially in infants at high risk of IVH . Innovations are needed to significantly reduce WBV during neonatal transport which can then be studied in appropriately powered clinical trials.…”

“…These infants are already at risk of neurological problems including intraventricular haemorrhage (IVH) and seizures that can lead to abnormal neurodevelopmental outcome. The underlying risks of infants’ gestation and/or pathology are compounded by the transport environment with exposure to noise, whole‐body vibration (WBV), accelerative and decelerative forces and variable thermal environment …”

Finding Comfortable Routes for Ambulance Transfers of Newborn Infants

“…Compared to non-transported premature infants, transported babies have more severe brain injury [1], [2], [3]. While the reasons for this are not fully understood, studies have shown that both vibration and noise are at excessive and potentially harmful levels inside ambulances [4], [5], [6], [7]. A reduction in these environmental stressors could improve outcomes.…”