Pulmonary Capillary Hemorrhage Induced by Diagnostic Ultrasound in Ventilated Rats

Publication date: August 2018
Source:Ultrasound in Medicine & Biology, Volume 44, Issue 8
Author(s): Douglas L. Miller, Zhihong Dong, Chunyan Dou, Krishnan Raghavendran
Pulmonary capillary hemorrhage (PCH) can be induced by diagnostic ultrasound—a potential safety issue. Anesthetized rats were intubated for intermittent positive-pressure ventilation (IPPV) with 0 end-expiratory pressure, +4 cm H2O end-expiratory pressure (PEEP) and −4 cm H2O end-expiratory pressure (NEEP). Rats were imaged at 7.6 MHz with a Philips HDI 5000 ultrasound machine. The output was low (mechanical index [MI] = 0.22) for aiming and then was raised for 5 min in 20 different exposure groups with n = 8. Peak rarefactional pressure amplitudes were measured in water and de-rated for chest attenuation. The PCH areas were measured on the lung surface. At 2.2 MPa, PCH was 9.3 ± 6.6 mm² for IPPV, 1.6 ± 3.2 mm² for PEEP (p < 0.001) and 26.8 ± 6.4 mm² for NEEP (p < 0.001). Thresholds were 1.3 MPa for IPPV, 2.1 MPa for PEEP and 1.0 MPa for NEEP. The small ventilator pressures subtracted or added to trans-capillary stress generated by diagnostic ultrasound pulses, virtually eliminating PCH for PEEP but enhancing PCH for NEEP.



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