Effects of spontaneous, assisted, and controlled ventilatory modes in halothane-anesthetized geldings.

This research article investigates how different modes of ventilation – spontaneous, assisted, and controlled – affect the cardiopulmonary functions in six healthy, anesthetized young male horses (geldings). The findings indicate that spontaneous and assisted modes result in better cardiac output than the controlled ventilation mode and allow for better oxygenation in the bloodstream.

Study Design and Execution

• The researchers performed the experiment on six healthy young geldings, who were laid down on their sides (lateral recumbency) and anesthetized with a constant dose of halothane.
• All modes of ventilation – spontaneous, assisted, and controlled – were applied at least once during each anesthetic exposure to every horse.
• The effects of these different modes on cardiopulmonary variables were then observed and recorded.

Cardiac Output Results

• The study found no significant difference in cardiac output between spontaneous and assisted ventilation modes.
• However, both these modes led to significantly higher cardiac output compared to controlled ventilation.

Partial Pressure of Carbon Dioxide (PaCO2) Results

• All modes of ventilation led to significant differences in the partial pressure of carbon dioxide (PaCO2).
• Under controlled ventilation, the PaCO2 was maintained at normal levels.
• Assisted ventilation resulted in a reduced PaCO2 as compared to spontaneous ventilation, but caused less cardiovascular depression than controlled ventilation.

Mixed Venous Oxygen Tensions

• The tension levels of oxygen mixed in the venous blood were found to be higher in horses under spontaneous and assisted ventilation modes compared to those under controlled ventilation.

Ventilation Variables

• Except for a shorter inspiratory time and a smaller ratio between inspiratory and expiratory phases associated with spontaneous ventilation, there were no notable effects of any mode on other ventilation-related variables.