Respiratory pattern and activity of the abdominal muscles after upper abdominal surgery

Because only few data is as yet available concerning abdominal muscle activity following upper abdominal surgery, the present study aimed to investigate the pattern of abdominal muscle activity before and after upper abdominal surgery and to relate any changes to differences in abdominal respiratory movements. Eight ASA I patients (5 women, 3 men), mean age 44 +/- 12 yr, undergoing elective cholecystectomy (midline incision) were investigated. The following parameters were measured, with the patients supine and at rest, on the eve of surgery, and 2, 4, 24 and 72 h afterwards: tidal volume (VT), breathing rate (f), inspiratory time (TI), total cycle time (TT), changes in abdominal (Dab) and thoracic (Drc) circumferences, surface electromyograms of the rectus abdominis and obliquus externus abdominis muscles. The ratio (Dab/Dab + Drc) was used as an index of relative abdominal movement. Anaesthetic management was similar for all patients (thiopentone, fentanyl, vecuronium, halothane and N2O). A significant reduction in VT was found between 2 and 24 h postoperatively, with a significant increase in f between 4 and 24 h after surgery. Both these parameters returned to normal values at the 72nd h. Relative abdominal movement was reduced in the immediate postoperative period (2 and 4 h), slowly improving, but remaining lower than normal at 72 h. Muscle tonus was increased at 2 h and returned to normal at the 4th h. This transient increase suggested a residual effect of fentanyl.(ABSTRACT TRUNCATED AT 250 WORDS)