A 56-year-old male patient’s status has gotten worse over the past 2 hours. He went from an air entrainment mask to a nonrebreather, and is now receiving positive pressure ventilation with the following settings:

The ventilator settings appear to be set properly because the ABG results tell us that the patient’s ventilatory status is good, being that the pH and PaCO2 are in the normal ranges. This issue here is with the patient’s oxygenation.

The PaO2 and SpO2 are extremely low, especially considering that the patient is receiving an FiO2 of 100%. This is a classic case of refractory hypoxemia that is most likely caused by intrapulmonary shunting.

We know that this is the case because the patient is not responding to high levels of oxygen. The patient needs PEEP in this case.

So by using what we know about intrapulmonary shunting, we can determine that the correct answer has to be D.

The correct answer is: D. A significant intrapulmonary shunt