How can hypoxemia due to shunting during one-lung ventilation be treated?

How can hypoxemia due to shunting during one-lung ventilation be treated?

During an open thoracotomy, the most effective treat-ment for hypoxemia during one-lung ventilation is the administration of continuous positive airways pressure (CPAP) with oxygen to the nondependent (collapsed) lung. The CPAP does lead to some distention of the lung, which is not usually a problem during an open thoraco-tomy if the amount of CPAP is small (e.g., 5 cm H₂O). However, during VAT, even a small amount of CPAP can make it difficult for the surgeon to operate.

An alternative to the application of CPAP to the non-dependent lung is positive end-expiratory pressure (PEEP) to the dependent ventilated lung. PEEP will help to prevent atelectasis that may worsen shunting.

During one-lung ventilation, 100% oxygen is adminis-tered. In some cases, the patient may have received chemotherapeutic agents, such as bleomycin, which may predispose them to pulmonary oxygen toxicity. In these cases, 100% oxygen should still be administered at the onset of one-lung ventilation, and then the FIO₂ may be reduced, as tolerated, according to pulse oximetry (SpO₂) monitoring.

It may be necessary to accept a lower SpO₂ during VAT, due to the reduced ability to provide treatment. Thus, a balance must be struck between the surgical need for a deflated lung and the oxygenation needs of the patient.