The effect of aminophylline on diaphragm blood flow in the piglet.

The effect of aminophylline on diaphragmatic blood flow was investigated in two groups of newborn piglets. Six animals were studied during spontaneous breathing and seven additional animals were paralyzed and ventilated to assess the effect of aminophylline on blood flow to the nonworking diaphragm. Arterial blood gases and pH, cardiac output, and diaphragmatic blood flow were measured before and 20 min after infusion of 20 mg/kg aminophylline. Blood theophylline concentrations averaged 117 mumols/L (21 micrograms/mL) in both groups of animals. Heart rate increased significantly in all animals. Cardiac output increased significantly only in spontaneously breathing animals. Aminophylline had no effect on blood flow to the costal or crural portions of the diaphragm in either the paralyzed or spontaneously breathing animals.