Tracking Limb Movement in Preterm Infants Using an Inertial Measurement Bracelet

Preterm infants are monitored continuously in the neonatal intensive care unit (NICU), often for weeks to months. Cardiac and respiratory signals are routinely collected to enable detection and early interventions that mitigate a wide range of complications associated with prematurity. Neurological monitoring is often lacking in the NICU despite the high risk of neurological sequelae including motor and cognitive disorders. Here we report our design and implementation of a wireless wearable device for quantifying limb movements of preterm infants. The Limb Inertial Measurement Bracelet for Infant Tracking (LIMBIT) is a thin, flexible, 3-gram bracelet placed around the infants' wrists and ankles for continuous measurement of limb motion. Three-dimensional acceleration and angular velocity are recorded using the device's inertial measurement unit (IMU). Ultra-low battery consumption is achieved through an embedded system architecture with a power-saving algorithm for optimal interplay between the accelerometer and gyroscope sensors. With a battery life of several days, we demonstrate the feasibility of accurate longitudinal and continuous recordings in the NICU. Movement signals are synchronized with other routinely collected health signals. The device's size, weight, flexibility, and integration within soft, sterile materials allows for a safe and non-invasive recording method in the NICU. LIMBITs enable the study of movement as a physiological vital sign and, like other vital signs, may enable more accurate detection and forecasting of adverse events as well as improved motor and cognitive outcomes in preterm infants.