Comparative Study of Diaphragmatic Function in Acute Necrotizing Pancreatitis (ANP) and Acute Peritonitis in Rats

Respiratory failure is a common and often lethal complication of acute necrotizing pancreatitis (ANP) and severe acute peritonitis. Because these two acute inflammatory processes develop in abdomen, adjacent to the diaphragm, we hypothesized that the two inflammatory processes might directly compromise diaphragm function. We tested this hypothesis using male rats models of ANP and acute peritonitis. ANP was induced by intraparenchymal pancreatic infiltration of bile salt solution: 0.3 ml 5%/100 gm BW; while acute peritonitis was induced by only inoculation 1 ml/kg of faecal suspension (2:1 W/V in saline) into peritoneal cavity. We assessed the diaphragm function in vitro using strips from control ANP and acute peritonitis. Contractile parameters of diaphragm included maximal twitch force (AY), contraction time (AX), half relaxation time (1/2 RT), height of isotonic contraction diaphragmatic endurance (T50%) index. We also assessed the peripheral muscle contractile properties in vitro in both ANP and acute peritonitis to determine whether affect skeletal muscle function or just a local condition. It was found that ANP and acute peritonitis were associated with significant reduction of AY 1/2 RT of isometric contraction and significant reduction of height of contraction, T50% of isotonic contraction of diaphragm. However, there was no significant change in peripheral muscle function in ANP group, while there was significant change in acute peritonitis. Moreover, the diaphragm dysfunction was more in acute peritonitis than in ANP: We concluded that ANP causes impairment in diaphragmatic function whereas peripheral muscle is spared. Meanwhile, peritonitis results in impairment in both diaphragmatic and peripheral muscle functions. Thus, the diaphragmatic dysfunction limit the ventilatory reserve of patients with pancreatitis and peritonitis and predisposing them to respiratory failure.