(634.8) Quantifying movement in ultrasound imagery of the hepatic-piston pulmonary apparatus in the American alligator (Alligator mississippiensis)

Poster Board Number: C83
Introduction: AAA has separate poster presentation times for odd and even posters.
Odd poster #s – 10:15 am – 11:15 am
Even poster #s – 11:15 am – 12:15 pm

Clinton Grand Pre (LSU HSC), William Thielicke (Optolution Messtechnik GmbH), Brandon Hedrick (LSU HSC), Ruth Elsey (Louisiana Department of Wildlife and Fisheries), Emma Schachner (LSU HSC)

Crocodilians ventilate their lungs using a novel respiratory mechanism called the hepatic-piston apparatus. Previous work presumes that the hepatic-piston pump is facilitated by a smooth thoracodorsal ceiling. However, the sliding and displacement of the pleura has never been confirmed in living crocodilians. Using ultrasound we recorded images of the lung pleura, liver, and viscera freely sliding cranially and caudally in seven individuals (n=7) of Alligator mississippiensis. Currently, there are no marketed software packages available for use with sonography equipment to quantitatively measure movement in ultrasound videos. To accurately quantify pleural displacement, we used modified cross-correlation functions from PIVlab, an open-source program for particle image velocimetry (PIV). This technology is most often used to trace velocity of particles in fluids. Here we successfully implemented this technology to trace the coherent textures in ultrasound videos and measure lung and visceral displacement. We verified our results with screen captures that included scale bars of the most cranial and caudal positions of the liver during ventilation, a landmark clearly visible in ultrasound. In each animal, 16 second ultrasound videos were collected 1) in a calm, resting state with shallow breaths, and 2) inspiring a 5% CO2 fixed N2 gas to invoke deep breathing. Data were collected at an axillary position, a thoracic position, the pleural/hepatic boundary, and a post-hepatic position. The ultrasound recordings show that in every instance, the pleura slides during ventilation. The total displacement varies based on two primary factors: 1) while breathing the 5% CO2 fixed N2 gas each individual took deeper breaths and the amount of pleura displacement increased and 2) there is a spatial gradient of displacement cranially to caudally, with minimal movement in the most cranial aspect of the lung and maximum movement caudally.