Hemodynamic effects of different modes of mechanical ventilation in acute cardiac and pulmonary failure: an experimental study.
OBJECTIVE
To determine the hemodynamic effects of four different modes of mechanical ventilation in an animal model of acute cardiac and pulmonary failure.


METHODS
Prospective, randomized, crossover design.


METHODS
University research laboratory.


METHODS
Twelve piglets weighing 10 to 16 kg.


METHODS
The experimental protocol consisted of three stable 30-min periods: when ventricular and pulmonary functions were normal (control), after the induction of acute cardiac failure by the administration of a beta-adrenergic receptor blocker, and after pulmonary failure induced by repeated lung lavage. Modes of mechanical ventilation included controlled mechanical ventilation, high-frequency oscillation, synchronized high-frequency jet ventilation, and external negative pressure oscillation combined with pressure support ventilation. Each mode of respiratory support was randomly and sequentially applied to each animal with the assessment of cardiopulmonary function at the end of each period.


RESULTS
Continuous monitoring included electrocardiogram, right atrial, left ventricular end-diastolic, pulmonary arterial, intrathoracic aortic, arterial, esophageal, and transpulmonary pressures and arterial and mixed venous oxygen saturation measurements. In addition, cardiac output using the thermodilution technique was measured intermittently. Whereas in the control period cardiac index was significantly (p < .05) higher during synchronized high-frequency jet ventilation (193 +/- 19.3 mL/kg/min) than during controlled mechanical ventilation (151 +/- 12.1 mL/kg/min) and high-frequency oscillation (151 +/- 18.1 mL/kg/min), there was no significant hemodynamic difference between the four modes of mechanical ventilation in the cardiac and pulmonary failure periods. In the pulmonary failure period, transpulmonary pressure was significantly higher during high-frequency oscillation (7.1 +/- 1.6 mm Hg) than during controlled mechanical ventilation (5.6 +/- 0.6 mm Hg), high-frequency ventilation (4.1 +/- 0.4 mm Hg), and external negative pressure oscillation combined with pressure support ventilation (5.3 +/- 0.5 mm Hg).


CONCLUSIONS
Synchronized high-frequency ventilation improves cardiac performance in control conditions. No hemodynamic difference is present between the four modes of mechanical ventilation in the cardiac and pulmonary failure periods. External negative pressure oscillation combined with pressure support ventilation has moderate hemodynamic advantages over controlled mechanical ventilation and high-frequency oscillation in different clinical settings, but it also results in a deterioration of pulmonary gas exchange during the pulmonary failure period.
Zobel
G
G
Department of Pediatrics and Cardiac Surgery, University of Graz, Austria.
Dacar
D
D
Rödl
S
S
D000818:Animals; D018592:Cross-Over Studies; D004195:Disease Models, Animal; D005260:Female; D006323:Heart Arrest / Q000628:therapy*; D006439:Hemodynamics; D006611:High-Frequency Jet Ventilation; D006612:High-Frequency Ventilation; D008297:Male; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods*; D012131:Respiratory Insufficiency / Q000628:therapy*; D013552:Swine