Regional tracheal blood flow during conventional and high-frequency jet ventilation in suckling pigs

OBJECTIVETo determine whether intubation and ventilation with either conventional mechanical ventilation or high-frequency jet ventilation, using dry or humidified gas, could induce regional tracheal ischemia and serve as a basis for the tracheal necrosis observed clinically during ventilation. DESIGNProspective, multiple group, controlled experimental study. SETTINGMedical school research laboratory. SUBJECTSTwenty, 3- to 5-wk-old suckling pigs. INTERVENTIONSAnesthetized, closed-chest piglets were intubated and ventilated for 30 mins with conventional mechanical ventilation and then ventilated for 2 additional hrs with either conventional mechanical ventilation or high-frequency jet ventilation. Groups were also ventilated, using both modes of ventilation, with either 37 degrees C humidified gas or 25 degrees C dry gas. MEASUREMENTS AND MAIN RESULTSBlood flow groups were compared during spontaneous breathing, conventional mechanical ventilation, high-frequency jet ventilation and both ventilation modes, using 37 degrees C humidified or 22 degrees C dry inspired gas. Groups were compared, using an analysis of variance with a Newman-Keul's post-test. Regional tracheal blood flow was measured, using radioactive microspheres. Cardiac output and organ blood flows were also monitored. Tracheal blood flow increased 10.3-fold within 30 mins after intubation, but there were no significant differences in regional or total tracheal blood flow between conventional mechanical ventilation and high-frequency jet ventilation, using 37 degrees C humidified gas. Tracheal blood flow was increased further using high-frequency jet ventilation and 25 degrees C dry gas but not conventional mechanical ventilation with dry gas. Although ventilation reduced cardiac output by approximate 30%, there were no significant differences in organ distribution between modes of ventilation. CONCLUSIONSAcute tracheal hyperemia occurred with intubation and ventilation with both conventional mechanical ventilation and high-frequency jet ventilation but no differences were observed between ventilation modes. Hyperemia was further increased with cool, dry inspired gas, using high-frequency jet ventilation but not conventional mechanical ventilation. Although acute tracheal ischemia was not produced by high-frequency jet ventilation or conventional mechanical ventilation, factors which alter the balance between arterial supply and metabolic demand or induce inflammation may contribute to the trach