Intermittent positive pressure ventilation (IPPV) should be continued after these changes are made, to allow washout of anaesthetic agents to occur.

During surgery, the ventilator-driven IPPV often results in a reduction in a patient’s PCO₂. The respiratory centre will not be stimulated if PCO₂ levels are low. In fact, in the presence of opioids, a PCO₂ greater than normal may be needed for respiratory drive to be adequate.

Reducing the minute ventilation at the end of a procedure (e.g. by simply turning down the respiratory rate) will allow PCO₂ levels to rise.