Lung Ultrasound Induction of Pulmonary Capillary Hemorrhage in Rats With Consideration of Exposimetric Relationships to Previous Similar Observations in Neonatal Swine

Abstract

Objective: Lung ultrasound (LUS) has become an essential clinical tool for pulmonary evaluation. LUS has been found to induce pulmonary capillary hemorrhage (PCH) in animal models, posing a safety issue. The induction of PCH was investigated in rats, and exposimetry parameters were compared with those of a previous neonatal swine study.

Methods: Female rats were anesthetized and scanned in a warmed water bath with the 3Sc, C1-5 and L4-12t probes from a GE Venue R1 point-of-care ultrasound machine. Acoustic outputs (AOs) of sham, 10%, 25%, 50% or 100% were applied for 5-min exposures with the scan plane aligned with an intercostal space. Hydrophone measurements were used to estimate the in situ mechanical index (MI_IS) at the lung surface. Lung samples were scored for PCH area, and PCH volumes were estimated.

Results: At 100% AO, the PCH areas were 73 ± 19 mm² for the 3.3 MHz 3Sc probe (4 cm lung depth), 49 ± 20 mm² (3.5 cm lung depth) or 96 ± 14 mm² (2 cm lung depth) for the 3.0 MHz C1-5 probe and 7.8 ± 2.9 mm² for the 7 MHz L4-12t (1.2 cm lung depth). Estimated volumes ranged from 378 ± 97 mm³ for the C1-5 at 2 cm to 1.3 ± 1.5 mm³ for the L4-12t. MI_IS thresholds for PCH were 0.62, 0.56 and 0.48 for the 3Sc, C1-5 and L4-12t, respectively.

Conclusion: Comparison between this study and previous similar research in neonatal swine revealed the importance of chest wall attenuation. Neonatal patients may be most susceptible to LUS PCH because of thin chest walls.

Keywords: B-lines; Bio-effects of ultrasound; Diagnostic ultrasound safety; Pulmonary ultrasound; Ultrasound dosimetry.