Gas exchange and haemodynamics during thoracotomy.

Area of Science:

• Cardiothoracic Surgery
• Respiratory Physiology
• Anesthesiology

Background:

• Thoracotomy involves opening the chest cavity, potentially affecting lung function and hemodynamics.
• Mechanical ventilation and double-lumen endotracheal tubes (Carlens' tube) are standard for single-lung ventilation during thoracic surgery.
• Understanding the physiological changes during thoracotomy is crucial for patient management.

Purpose of the Study:

• To investigate the effects of opening the pleura and subsequent lung surgery on cardiac index, systemic and pulmonary arterial pressures, and gas exchange.
• To assess changes in ventilation and carbon dioxide elimination in each lung during thoracotomy.
• To evaluate the impact on ventilation-perfusion mismatch (VD/VT) and overall hemodynamic stability.

Main Methods:

• Seventeen patients undergoing thoracotomy were studied in the lateral position.
• Mechanical ventilation was maintained using a Carlens' tube for selective lung ventilation.
• Measurements included cardiac index, arterial pressures, carbon dioxide elimination, ventilation, and end-tidal PCO2 for each lung.

Main Results:

• Opening the pleura increased cardiac index (12%) and carbon dioxide elimination/ventilation in the upper lung.
• Arterial pressure decreased during lung surgery, but pulmonary artery pressure remained unchanged.
• Ventilation-perfusion mismatch (VD/VT) decreased significantly upon opening the pleura.
• Surgical handling of the lung caused transient decreases in ventilation, compliance, and CO2 elimination in that lung.

Conclusions:

• Opening the pleura during thoracotomy improves ventilation-perfusion matching.
• Neither pleural opening nor lung surgery caused clinically significant hemodynamic or oxygenation derangements when both lungs were ventilated.
• These findings support the safety of current ventilation strategies during thoracotomy.