Effects of digoxin on regional diaphragm function after thoracotomy in awake sheep

Abstract

The effects of digoxin on diaphragmatic contraction were studied in 12 sheep, with 6 days after a right thoracotomy, during the period of intense diaphragmatic inhibition. Diaphragmatic function was assessed by implanting sonomicrometry crystals and electromyographic (EMG) electrodes in both the coastal and crural diaphragmatic regions. Awake sheep were studied before and after intravenous digoxin (0.4 mg/ kg) during both quiet breathing (QB) and during CO 2 rebreathing, until the fractional concentration of expired CO 2 ( Fet CO 2 ) reached 0.10. After digoxin infusion, during both QB and at Fet CO 2 of 0.10, esophageal and transdiaphragmatic pressures increased ( P<0.05). After digoxin infusion no changes were measured for end-expiratory resting length, shortening fraction, shortening velocity or EMG activity of either diaphragmatic segment or for respiratory frequency, ventilation, tidal volume and Fet CO 2 . We conclude that intravenous digoxin given to awake sheep after a thoracotomy increases P di, but noes not alter diaphragmatic shortening nor alter the level of diaphragmatic activation either QB or at Fet CO 2 of 0.10.