An implantable electronic device for monitoring fetal lung pressure in a lamb model of Congenital Diaphragmatic Hernia

Tracheal occlusion (TO) is one fetal treatment option for congenital diaphragmatic hernia. It aims to reduce lung hypoplasia and hypertension by occluding the trachea with a subsequent increase in pulmonary pressure. However, how TO affects lung pressure is unknown and no devices are available for its measurement. We developed an implantable device for real-time wireless monitoring and long-term logging of lung pressure in ovine fetuses. The device comprised a microcontroller unit, two pressure sensors, an inertial measurement unit (IMU), a radio-frequency unit, and an antenna. In-vitro and in-vivo tests were performed to evaluate device performances. A diaphragmatic hernia was created in ovine fetuses via hysterotomy. Nine devices were implanted at 100 days gestation and remained until delivery (~142 d). One pressure sensor measured pressure in the amniotic sac and the other in the fetal trachea. In-vitro pressure accuracy was median (interquartile range) 0.31% (0.1%). In-vitro device lifetime was ~60 days. The in-vivo device recording time was 26.0 (3.9) days and it was well tolerated by the fetus and the ewe. Data telemetry operated throughout the device lifetime. At delivery, amniotic fluid, device encapsulation and lamb skin did not present evidence of damages. Pressure data in 4 lambs were analysed. Fast pressure changes due to the spontaneous fetal activity and long-term mean pressure changes resulting from TO were detected. The IMU allowed for the assessment of changes in fetal position. This device allows long-term monitoring of mean lung pressure, spontaneous breathing activity, and movements in physiological and pathological ovine fetal models.