Right Ventricular Function During One-lung Ventilation: The Effects of Pressure Controlled and Volume Controlled Ventilation

One-lung ventilation (OLV) provides excellent operative field for thoracic procedures, but is opposed by the harmful impairment of cardiac index and right ventricular (RV) function which may influence postoperative morbidity and mortality. In our previous study, we demonstrated significant reductions in RV ejection fraction (REF) and CI values after the initiation of OLV attributable to the increased right ventricular afterload, stroke work and end-diastolic volume augmented by increased airway pressures. This may be harmful with the patients with advanced obstructive lung diseases and those with pulmonary hypertension. Thus there is no doubt that decreases in airway pressures will be associated with better RV function.

Volume controlled ventilation (VCV) is the commonly used traditional ventilation mode for OLV during thoracic procedures but its use is associated with deleterious increases in airway pressure which may impede RV function.

Pressure controlled ventilation (PCV) is an alternative mode of ventilation which is widely used in the patients with acute respiratory distress syndrome (ARDS) and acute lung injury (ALI), whereby high initial flow rates are delivered to quickly achieve and maintain the set inspiratory pressure followed by rapidly decelerating flow.These high initial flow rates lead to a more rapid alveolar inflation.

PCV has been suggested as a useful tool to improve oxygenation as well as decreases in intra-pulmonary shunt (Qs/Qt) and airway pressures compared with VCV during OLV for patients undergoing thoracic surgery. Whereas, others demonstrated comparable arterial oxygenation with the use of PCV and VCV during OLV.

However, the use of PCV offers advantages over VCV during OLV in the term of reducing mean and bronchial peak airway pressures and intrapulmonary shunt, hence limiting the risk for barotrauma and impaired RV function.