The effects of increasing the fractional concentration of oxygen in the inspired gas to 1.0 on intrapulmonary shunting (Qsp) was evaluated in 82 intubated cardiovascularly stable patients in intensive care, regardless of airway pressure therapy or preexistent pulmonary pathologic abnormalities. Intrapulmonary shunting following administration of 100% oxygen increased in 132 of 140 measurements, decreased in seven, and remained unchanged in one measurement. The direction of change of Qsp with 100% oxygen shows no correlation with either airway pressure therapy or preexisting pulmonary disease.
