Effects of body position and extension of the neck and extremities on lung volume measured via computed tomography in red-eared slider turtles (Trachemys scripta elegans)

Objective: To determine the effects of body position and extension of the neck and extremities on CT measurements of ventilated lung volume in red-eared slider turtles (Trachemys scripta elegans). Design: Prospective crossover-design study. Animals: 14 adult red-eared slider turtles. Procedures: CT was performed on turtles in horizontal ventral recumbent and vertical left lateral recumbent, right lateral recumbent, and caudal recumbent body positions. In sedated turtles, evaluations were performed in horizontal ventral recumbent body position with and without extension of the neck and extremities. Lung volumes were estimated from helical CT images with commercial software. Effects of body position, extremity and neck extension, sedation, body weight, and sex on lung volume were analyzed. Results: Mean ± SD volume of dependent lung tissue was significantly decreased in vertical left lateral (18.97 ± 14.65 mL), right lateral (24.59 ± 19.16 mL), and caudal (9.23 ± 12.13 mL) recumbent positions, compared with the same region for turtles in horizontal ventral recumbency (48.52 ± 20.08 mL, 50.66 ± 18.08 mL, and 31.95 ± 15.69 mL, respectively). Total lung volume did not differ among positions because of compensatory increases in nondependent lung tissue. Extension of the extremities and neck significantly increased total lung volume (127.94 ± 35.53 mL), compared with that in turtles with the head, neck, and extremities withdrawn into the shell (103.24 ± 40.13 mL). Conclusions and Clinical Relevance: Vertical positioning of red-eared sliders significantly affected lung volumes and could potentially affect interpretation of radiographs obtained in these positions. Extension of the extremities and neck resulted in the greatest total lung volume