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 mechanical ventilation (CMV) and high frequency jet ventilation (HFJV) in experimental Fontan-circulation. Design: Prospective, randomized, crossover design. Setting: University research laboratory. Subjects: Ten pigs weighing 28-35 kg. Interventions: Modes of mechanical ventilation included CMV and HFJV ventilation. Both modes of respiratory support were randomly and sequentially applied to each animal with the assessment of cardiopulmonary function at the end of each period. Measurements and Results: Continuous monitoring included EGG, central venous, left atrial, mean pulmonary artery, mean arterial, and oesophageal pressures, flow recordings in both the pulmonary artery and the aorta, and arterial and mixed venous oxygen saturation measurements. In addition, cardiac output using the thermodilution technique was measured intermittently. During the development of the Fontan-model heart rate and central venous pressure increased significantly by 57% and 193%, respectively, whereas mean arterial pressure and cardiac output decreased significantly by 31% and 50%, respectively. In addition, arterial and mixed venous oxygen saturations decreased significantly by 7.3% and 29.5%, respectively. There was no significant difference in hemodynamic parameters between CMV and HFJV during Fontan-circulation. However, significant phasic hemodynamic changes, including decreases in central venous and arterial pressures associated with an increase in left atrial pressure, were observed during the inspiratory phase of CMV. Conclusions: In our experimental Fontan model both CMV and HFJV were equally effective in terms of gas exchange and hemodynamic support. During HFJV gas exchange was achieved at lower intrathoracic airway pressures which in contrast to CMV did not result in phasic hemodynamic changes during the respiratory cycle.