![]() 004) and characteristic impedance (167 +/- 12 vs. ![]() As the tidal volume was increased from 10 to 20 mL/kg, pulmonary vascular resistance (1351 +/- 94 vs. The decrease in dynamic compliance of 20% indicated the presence of pulmonary overdistention by definition. When compared with a tidal volume of 10 mL/kg, a tidal volume of 20 mL/kg resulted in a significant decrease in dynamic compliance from 10.5 +/- 0.9 to 8.4 +/- 0.6 mL/cm H2O (p =. ![]() We evaluated the pulmonary vascular and cardiac effects of the various tidal volume and PEEP settings by measuring pulmonary vascular resistance, pulmonary characteristic impedance, and cardiac output. Inspiratory time (0.75 sec), FIO2 (0.3), and minute ventilation were held constant. Tidal volumes and airway pressures were measured by a pneumotachometer and the Pediatric Pulmonary Function Workstation. At this baseline tidal volume, airway pressure-volume curves did not demonstrate pulmonary overdistention. Pulmonary overdistention was defined as a decrease in dynamic compliance of > or =20% when compared with a compliance measured at a baseline tidal volume of 10 mL/kg. The swine were ventilated and data were collected with delivered tidal volumes of 10, 15, 20, and 25 mL/kg and PEEP settings of 5 and 10 cm H2O in a random order. An ultrasonic flow probe was placed around the pulmonary artery. After median sternotomy, pressure transducers were placed in the right ventricle, pulmonary artery, and left atrium. Piglets with normal lungs were anesthetized, intubated, and paralyzed. Prospective, randomized, controlled laboratory trial.Įleven 4- to 6-wk-old swine, weighing 8 to 12 kg. An additional goal was to determine whether the effects of pulmonary overdistention are dependent on delivered tidal volume and/or positive end-expiratory pressure (PEEP, end-expiratory lung volume). The objective was to test the hypothesis that increasing tidal volumes adversely affect pulmonary vascular mechanics and cardiac output. In a pediatric swine model, the effects of increasing tidal volumes and the subsequent development of pulmonary overdistention on cardiopulmonary interactions were studied.
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