Effects of diaphragmatic plication on respiratory mechanics in dogs with unilateral and bilateral phrenic nerve paralyses.

To examine the effects of diaphragmatic plication on respiratory mechanics during spontaneous breathing, we grouped 28 dogs into left phrenicotomy and plication (group L, n = 11), bilateral phrenicotomy and plication (group B, n = 9), and sham operations (group C, n = 8). In groups L and B, phrenicotomy caused significant (p < 0.05) decreases in tidal volume (VT), transdiaphragmatic pressure (delta Pdi), the ratio of gastric to esophageal pressure (delta Pga/delta Pes) and dynamic lung compliance (Cdyn), and significant (p < 0.05) increases in esophageal pressure (delta Pes), and the work of breathing (WOB) per liter of ventilation. In group L, plication resulted in significant (p < 0.05) increases in VT, delta Pdi, delta Pga/delta Pes, and Cdyn, and a significant reduction of WOB compared with phrenicotomy condition, indicating an improvement in the respiratory mechanics. However, in group B, no significant changes were observed after plication except for increased VT. In eight left-phrenicotomized open-chest dogs, transdiaphragmatic pressure (Pdi) and fractional shortening (FS) of right hemidiaphragm by right phrenic nerve stimulation increased significantly (p < 0.05) after plication, compared with the phrenicotomy condition, suggesting more effective kinetics of the right hemidiaphragm after plication of the left hemidiaphragm. Our results showed that diaphragmatic plication for unilateral paralysis is more effective than for bilateral paralysis, indicating that an improvement in kinetics of the intact hemidiaphragm plays an important role in functional recovery.