SESSION TYPE: Diagnostic Bronchoscopy
PRESENTED ON: Tuesday, October 23, 2012 at 04:30 PM - 05:45 PM
PURPOSE: The induction of pulmonary hemorrhage (PH) by pulsed ultrasound was discovered over 20 yr ago, but seemed to pose little risk to patients because the lung was thought to be a poor candidate for ultrasound examination. Recently however, pulmonary ultrasound examination has become an important part of chest medicine, which impelled this reconsideration of the pulmonary hemorrhage issue.
METHODS: Anesthetized rats were prepared for ultrasound scanning and mounted in a 37 C water bath. A diagnostic ultrasound machine (HDI 5000, Philips Healthcare, Andover MA USA) with CL15-7 (~7.6 MHz) linear array was used to image the right lung. A low Mechanical Index (MI) setting of 0.21 was used to align the probe for a clear B mode view of the lung surface. For scanning in different groups of rats, the MI was raised to different higher levels, up to the maximum of MI=0.9, for 5 min. For a sham group, the rats were prepared and mounted in the water bath but not scanned. The real time image was recorded and the lungs were removed after scanning for evaluation of PH.
RESULTS: For MI=0.9, the image immediately displayed a growing comet tail artifact, which is diagnostic of alveolar fluid. This sign rapidly spread across the entire bright-line image of the lung surface. Upon examination, a contusion-like PH band was found on the lung, whose length corresponded to the width of the sign in the image. The signs appeared within seconds at MI=0.7 or 0.9, but more slowly at lower MIs. The proportion of positive results was statistically significant for MI=0.52 (4 of 5 rats, P<0.01) but not for MI=0.37 (2 of 5, P>0.1), relative to negative shams.
CONCLUSIONS: Pulmonary hemorrhage was induced in a rat model of diagnostic pulmonary ultrasound at moderate MIs.
CLINICAL IMPLICATIONS: Direct lung examination in point-of-care pulmonary ultrasound may carry a risk of pulmonary injury for some patients. More information will be needed to provide safety guidance, which retains the ability to obtain optimally diagnostic images.
DISCLOSURE: The following authors have nothing to disclose: Douglas Miller
No Product/Research Disclosure InformationUniversity of Michigan, Ann Arbor, MI