A Haptic Simulator for Training the Application of Range of Motion Exercise to Premature Infants

The range of motion exercise is an experimental therapy for improving bone and muscle growth in premature infants but little is known about the magnitude of pressures that must be applied to the limbs during this exercise to elicit a physiological benefit and novice caregivers currently must rely on subjective instruction to learn to apply appropriate pressures. The goal of this study was to quantify the pressures applied by experienced caregivers during application of this exercise and to create a haptic simulator that could be used to train novice caregivers such as parents to apply the same pressures. We quantified the pressure applied by two neonatal intensive care nurses (“experts”) to the wrists of nine newborn, premature infants of varying gestational ages using an infant blood pressure cuff modified to act as a finger pressure sensor. The experts applied statistically significant different pressures depending on gestational age but did not differ significantly between themselves in the pressure they applied. We then created a robotic simulator of the premature infant wrist and programmed it to respond with the measured pressure-angle properties of the actual infants’ wrists. The novice adult participants $(n=19)$ used the simulator to learn to apply target pressures for simulated wrists that corresponded to three different gestational ages. Training with the simulator for 30 min allowed the participants to learn to apply pressures significantly more like those of the experts. The performance improvement persisted at a retention test several days later. These results quantify for the first time the pressures applied during assisted exercise, include novel observations about joint flexibility and maturation early in life and suggest a strategy for teaching exercise intervention teams to provide assisted exercise within a more reproducible range using haptic simulation technology.