HEMODYNAMIC-EFFECTS OF CONVENTIONAL MECHANICAL VENTILATION AND HIGH-FREQUENCY JET VENTILATION IN FONTAN-CIRCULATION - AN EXPERIMENTAL-STUDY

Objective: To determine the hemodynamic effects of conventional mechan ical ventilation (CMV) and high frequency jet ventilation (HFJV) in ex perimental Fontan-circulation. Design: Prospective, randomized, crosso ver design. Setting: University research laboratory. Subjects: Ten pig s weighing 28-35 kg. Interventions: Modes of mechanical ventilation in cluded CMV and HFJV ventilation. Both modes of respiratory support wer e randomly and sequentially applied to each animal with the assessment of cardiopulmonary function at the end of each period. Measurements a nd Results: Continuous monitoring included EGG, central venous, left a trial, mean pulmonary artery, mean arterial, and oesophageal pressures , flow recordings in both the pulmonary artery and the aorta, and arte rial and mixed venous oxygen saturation measurements. In addition, car diac output using the thermodilution technique was measured intermitte ntly. During the development of the Fontan-model heart rate and centra l venous pressure increased significantly by 57% and 193%, respectivel y, whereas mean arterial pressure and cardiac output decreased signifi cantly by 31% and 50%, respectively. In addition, arterial and mixed v enous oxygen saturations decreased significantly by 7.3% and 29.5%, re spectively. There was no significant difference in hemodynamic paramet ers between CMV and HFJV during Fontan-circulation. However, significa nt phasic hemodynamic changes, including decreases in central venous a nd arterial pressures associated with an increase in left atrial press ure, were observed during the inspiratory phase of CMV. Conclusions: I n our experimental Fontan model both CMV and HFJV were equally effecti ve in terms of gas exchange and hemodynamic support. During HFJV gas e xchange was achieved at lower intrathoracic airway pressures which in contrast to CMV did not result in phasic hemodynamic changes during th e respiratory cycle.