OBJECTIVE:To test the hypothesis that a gel mattress is most effective in attenuating mechanical vibration in neonatal transport, we performed a randomized block study of four mattress combinations (none, foam, gel, gel on foam) using mannequins and an ambulance traveling on fixed routes (city, highway).
STUDY DESIGN:Mechanical vibration was assessed by measuring vertical accelerations at two locations: the forehead of a 2000-gm mannequin and the transport incubator base. From time histories of these accelerations, root mean square (RMS) values and power spectral density functions were calculated. The effect of the mattress on the transmission of vibration was determined from ratios of the RMS values at the two locations. An RMS ratio of Ͻ1.0 indicates attenuation, whereas a ratio of Ͼ1.0 indicates accentuation of vibration. From the power spectral density functions, the natural frequency of the system was determined for each mattress combination in relation to the natural frequencies of the ambulance. To determine the effect of the weight of the mannequin on vibration, additional measurements were performed using a 300-gm mannequin.
RESULTS:All the observed RMS ratios were Ͼ1. The highest ratios were observed on the city route in the absence of the gel mattress. The gel mattress, used alone or with the foam mattress, in contrast to foam or no mattress, shifted the natural frequency of the system away from the natural frequencies of the ambulance, avoiding a large amplification of vibration. A decrease in the weight of the mannequin caused the gel mattress to be less effective in attenuating vibration.
CONCLUSION:A gel mattress, used alone or with a foam mattress, results in the least accentuation of vibration, but vibration in ambulance transport is not attenuated by any of the mattress combinations. The hazard of vibration may be particularly relevant when transporting extremely low birth weight neonates. These findings indicate a need for study and design of more effective devices that can reduce the vibratory stress. Journal of Perinatology 2000; 5:307-310.In the perinatal health care system, sick newborn infants often are transported from community hospitals to specialized care facilities. It is also common to transport convalescing newborn infants back to community hospitals before home discharge. During these transports, infants are exposed to prolonged, low-frequency, high-amplitude mechanical vibration. [1][2][3] In adult humans and experimental animals, this vibration has adverse effects on cardiorespiratory function, 4 -8 the peripheral and central nervous system, 8 -10 electroencephalographic activity, 11 body temperature, 12 metabolic and endocrinologic function, 8 and the gastrointestinal system. 8 In addition, vibration may contribute to general discomfort, motion sickness, vomiting, and increased intracranial pressure 8,13 and may also compromise clinical observation. 14 Vibration has deleterious effects on pregnant women and fetuses. Vibration is associated with the risk of premature delivery in...
