Effect of inspiratory resistive loading on costal and crural diaphragm electromyograms in piglets

We examined the effect of inspiratory resistive loaded breathing (IRL) on the electromyographic (EMG) activity of the costal and crural diaphragm in nine anesthetized spontaneously breathing piglets (age 10-23 days, weight 2.8-4.4 kg). Bipolar wire electrodes were inserted into the anterior paratendinous costal diaphragm and the midportion of the crural diaphragm. EMG activity was quantified in arbitrary units (au) of peak moving time average while the animals breathed 50% O2/50% N2 (baseline) and during 30 min of IRL. Thirty min of IRL increased the peak moving time average of both parts of the diaphragm, with the increase in the crural EMG activity (from baseline: 22 +/- 2 to 30 min of IRL: 76 +/- 22 au) exceeding that of costal (from baseline: 23 +/- 2 to 30 min of IRL: 50 +/- 24 au), p less than 0.05. These results 1) suggest that the inspiratory EMG activity of the diaphragm can be differentially distributed between its costal and crural components and 2) document that crural inspiratory EMG activity undergoes greater augmentation under the condition of IRL than does the costal activity in piglets.