ORIGINAL ARTICLE Decreasing sound and vibration during ground transport of infants with very low birth weight J Prehn 1 , I McEwen 2 , L Jeffries 3 , M Jones 3 , T Daniels 4 , E Goshorn 4 and C Marx 4 OBJECTIVE: To measure the effectiveness of modifications to reduce sound and vibration during interhospital ground transport of a simulated infant with very low birth weight (VLBW) and a gestational age of 30 weeks, a period of high susceptibility to germinal matrix and intraventricular hemorrhage. STUDY DESIGN: Researchers measured vibration and sound levels during infant transport, and compared levels after modifications to the transport incubator mattresses, addition of vibration isolators under incubator wheels, addition of mass to the incubator mattress and addition of incubator acoustic cover. RESULT: Modifications did not decrease sound levels inside the transport incubator during transport. The combination of a gel mattress over an air chambered mattress was effective in decreasing vibration levels for the 1368 g simulated infant. CONCLUSION: Transport mattress effectiveness in decreasing vibration is influenced by infant weight. Modifications that decrease vibration for infants weighing 2000 g are not effective for infants with VLBW. Sound levels are not affected by incubator covers, suggesting that sound is transmitted into the incubator as a low-frequency vibration through the incubator’s contact with the ambulance. Medical transportation can apply industrial methods of vibration and sound control to protect infants with VLBW from excessive physical strain of transport during vulnerable periods of development. Journal of Perinatology (2015) 35, 110–114; doi:10.1038/jp.2014.172; published online 27 November 2014 INTRODUCTION Approximately 480 000 premature infants are born each year in the United States, with nearly 58 000 of these weighing less than 1500 g, thus being classified as having very low birth weight (VLBW). 1 Because perinatal care in the United States of America is regionalized, preterm infants who have VLBW and are born at outlying hospitals are routinely transported to tertiary care facilities soon after delivery. Infants with VLBW who are transported are more likely to experience an intraventricular hemorrhage (IVH) than non-transported infants, and any IVH that occurs is likely to be more severe than the one experienced by infants born at tertiary care facilities. 2,3 These transported infants are subsequently at a higher risk for significant neuro- developmental complications than the non-transported infants. Evidence suggests that the physical strain of the transport process is a contributing factor in neurodevelopmental sequelae among transported infants with VLBW. 4 Premature infants, especially those with VLBW, are at risk for germinal matrix hemorrhage and IVH. Between 23 and 34 weeks gestational age, increased vascularization of the germinal matrix to support brain cell proliferation and migration increases the risk of hemorrhage. 5 Infants with VLBW are most vulnerable to hemorrhage during the first 24 to 72 h following birth, 6 which is the time they are most likely to be transported. 7 Preterm infant sensory system development contributes to additional risk factors. By 28 weeks gestation, the preterm infant has functional auditory and vestibular systems; 8 however, systems that provide habituation to sensory stimulation are not mature, leaving the preterm infant unable to adapt to sensory input. 9 Premature infants respond negatively to intense sensory stimulation 10 such as sudden, loud sound that can produce an increase in respiration and heart rates, increase in intracranial pressure and decrease in oxygenation. 11 Sound is measured in decibels (dB) or in ‘A’ weighted decibels (dBA). The American Academy of Pediatrics (AAP) recommends sound levels inside incubators to be 45 dBA or less. 12 Neonatal transports exceed these guidelines, producing high auditory stimulation with sound levels ranging from 60 to 90 dBA. 13,14 Interhospital ground transport also exposes infants to intense vibratory stimulation. 15 No standards exist for infant exposure to vibration; instead, researchers use International Standards Organization (ISO) guidelines for seated adults’ perceptions of whole body vibration as a guideline for infants. 16 Whole body vibration is measured as acceleration and is reported as root mean square (RMS) acceleration, with the highest level of vibration during a timed sample as the peak acceleration. 16 Several studies have attempted to quantify and decrease the vibration levels that infants experience during interhospital ground transport. Two US studies used neonatal cardio-pulmonary resuscitation mannequins as models for the infants inside the transport incubators and compared the mannequin vibration levels with ISO guidelines. 15,17 Mannequin vibration levels were 1.8 to 6 m s - 2 , and would have been perceived as very to extremely uncomfortable by the seated adults. 15–17 Vibration frequencies were less than 20 Hz. 15 These studies were conducted in the United States, and used truck base diesel engine ambulances. 15,17 Studies conducted in Europe, however, used van-type ambulances and reported vibration levels of 0.25 to 0.6 m s - 2 . 14,18 This suggests that the mechanical vibration originating from the ambulance and the interface of the ambulance and the road is more problematic in the diesel engine truck base ambulances commonly used in the 1 School of Physical Therapy, William Carey University, Hattiesburg, MS, USA; 2 Department of Rehabilitation Science, Health Sciences Center, University of Oklahoma, Oklahoma City, OK, USA; 3 Health Sciences Center, University of Oklahoma, Oklahoma City, OK, USA and 4 University of Southern Mississippi, Hattiesburg, MS, USA. Correspondence: Dr J Prehn, School of Physical Therapy, William Carey University, WCU 9, 498 Tuscan Avenue, Hattiesburg, MS 39401, USA. E-mail: judypedpt@bellsouth.net Received 13 March 2014; revised 27 July 2014; accepted 5 August 2014; published online 27 November 2014 Journal of Perinatology (2015) 35, 110 – 114 © 2015 Nature America, Inc. All rights reserved 0743-8346/15 www.nature.com/jp