During one-lung ventilation with a double-lumen endotracheal tube, which maneuver is least likely to raise the PaO2 after proper tube placement?

During one-lung ventilation with a double-lumen endotracheal tube, which maneuver is least likely to raise the PaO2 after proper tube placement?

• A. CPAP to the non-dependent lung
• B. PEEP to the dependent lung
• C. Clamping the pulmonary artery by the surgeon during pneumonectomy
• D. Continuous infusion of epoprostenol (Flolan) via a central line

Answer: (D)

In one-lung ventilation the key to arterial oxygen is limiting shunt through the nonventilated lung while keeping perfusion directed to the ventilated lung. By delivering CPAP to the nondependent (nonventilated) lung, you recruit and oxygenate that lung, reducing the amount of blood that bypasses ventilated air and thus increasing PaO2. Applying PEEP to the dependent, ventilated lung helps keep that lung open and well-ventilated, which also improves oxygenation. When the surgeon clamps the pulmonary artery to the nonventilated lung during pneumonectomy, you dramatically cut off blood flow to that lung, dramatically reducing shunt and boosting PaO2. Infusing epoprostenol systemically via a central line, however, provides nonselective pulmonary vasodilation. This can increase blood flow to both lungs, including the nonventilated one, potentially worsening V/Q mismatch and not reliably raising PaO2. Inhaled vasodilators would have a different, more selective effect, but the intravenous route lacks that selectivity, making it least likely to raise PaO2.

In one-lung ventilation the key to arterial oxygen is limiting shunt through the nonventilated lung while keeping perfusion directed to the ventilated lung. By delivering CPAP to the nondependent (nonventilated) lung, you recruit and oxygenate that lung, reducing the amount of blood that bypasses ventilated air and thus increasing PaO2. Applying PEEP to the dependent, ventilated lung helps keep that lung open and well-ventilated, which also improves oxygenation. When the surgeon clamps the pulmonary artery to the nonventilated lung during pneumonectomy, you dramatically cut off blood flow to that lung, dramatically reducing shunt and boosting PaO2.

Infusing epoprostenol systemically via a central line, however, provides nonselective pulmonary vasodilation. This can increase blood flow to both lungs, including the nonventilated one, potentially worsening V/Q mismatch and not reliably raising PaO2. Inhaled vasodilators would have a different, more selective effect, but the intravenous route lacks that selectivity, making it least likely to raise PaO2.