Lung Ultrasound Induction of Pulmonary Capillary Hemorrhage in Neonatal Swine

This study investigated induction of pulmonary capillary hemorrhage (PCH) in neonatal pigs (piglets) using three different machines: a GE Venue R1 point-of-care system with C1-5 and L4-12t probes, a GE Vivid 7 Dimension with a 7L probe and a SuperSonic Imagine machine with an SL15-4 probe and shear wave elastography (SWE). Female piglets were anesthetized, and each was mounted vertically in a warm bath for scanning at two or three intercostal spaces. After aiming at an innocuous output, the power was raised for a test exposure. Hydrophone measurements were used to calculate in situ values of mechanical index (MI_IS). Inflated lungs were removed and scored for PCH area. For the C1-5 probe at 50% and 100% acoustical output (AO), a PCH threshold of 0.53 MI_IS was obtained by linear regression (r² = 0.42). The L4-12t probe did not induce PCH, but the 7L probe induced zones of PCH in the scan planes. The Venue R1 automated B-line tool applied with the C1-5 probe did not detect PCH induced by the C1-5 probe as B-line counts. However, when PCH induced by C1-5 and 7L exposures were subsequently scanned with the L4-12t probe using the automated tool, B-lines were counted in association with the PCH. The SWE induced PCH at push-pulse positions for 3, 30 and 300 s of SWE with PCH accumulating at 0.33 mm²/s and an exponential rise to a maximum of 18.4 mm² (r² = 0.61). This study demonstrated the induction of PCH by LUS of piglets, and supports the safety recommendation for use of MIs <0.4 in neonatal LUS.