Hemodynamic and respiratory effects of positive end-expiratory pressure during a pulmonary distress model in isoflurane anesthetized swine

ABSTRACT

Background: Several pulmonary and hemodynamic complications may occur during mechanical ventilation of the lungs. The use of a positive end-expiratory pressure (PEEP) can improve oxygenation and prevent atelectasis, although this method can cause important hemodynamic side effects. Mostly, these hemodynamic effects are due to increased airway pressure that is transferred to the intrapleural space, increasing the intrathoracic pressure, which decreases venous return to the heart. Cardiac output is significantly reduced with high PEEP levels which in turn precludes the improvement effects on blood oxygenation. The aim of this study was to evaluate hemodynamic and respiratory effects of different levels of carbon dioxide insufflations associated with different levels of PEEP under conventional two-lung ventilation in isoflurane anesthetized pigs.Materials, Methods & Results: Twelve juvenile pigs were anesthetized with ketamine and midazolam, and end tidal isoflurane 2.0 V% for maintenance. Animals were submitted to tension pneumothorax through an acute intrathoracic insufflation with carbon dioxide at 0, 5, and 10 mmHg. Mechanical lung ventilation with 100% oxygen was started with zero PEEP then increased to 5 and 10 cmH2 O. Ventilatory, respiratory and hemodynamic parameters were measured, as well as blood gases. Tension pneumothorax of 10 mmHg, with both PEEP levels, induced...(AU)