The effects of intrathoracic pressure during continuous two-lung ventilation for thoracoscopy on the cardiorespiratory parameters in sevoflurane anaesthetized dogs.

The cardiopulmonary effects of different levels of carbon dioxide insufflation (3, 5 and 2 mm Hg) under two-lung ventilation were studied in six sevoflurane (1.5 minimum alveolar concentration; MAC) anaesthetized dogs during left-sided thoracoscopy. An arterial catheter, Swan-Ganz catheter and multianaesthetic gas analyser were used to monitor the cardiopulmonary parameters during the experiment. Baseline data were obtained before intrathoracic pressure elevation and the measurements were repeated at intervals after left lung collapse induced by insufflation with carbon dioxide gas. The intrapleural pressure levels used were 3, 5 and 2 mm Hg. Arterial blood pressures, cardiac index, stroke index, left and right ventricular stroke work index, arterial haemoglobin saturation, arterial oxygen tension and systemic vascular resistance decreased significantly during hemithorax insufflation, whereas heart rate, right atrial pressure, mean, systolic and diastolic pulmonary arterial pressure, pulmonary capillary wedge pressure, pulmonary vascular resistance and arterial carbon dioxide tension significantly increased during intrapleural pressure elevation. Although carbon dioxide insufflation into the left hemithorax with an intrapleural pressure of 2-5 mm Hg compromises cardiac functioning in 1.5 MAC sevoflurane anaesthetized dogs, it can be an efficacious adjunct for thoracoscopic procedures. Intrathoracic view was satisfactory with an intrapleural pressure of 2 mm Hg. Therefore, the intrathoracic pressure rise during thoracoscopy with two-lung ventilation should be kept as low as possible. Additional insufflation periods should be avoided, since a more rapid and more severe cardiopulmonary depression can occur.