Orca inhaled oxygen and exhaled carbondioxide just like humans and other mammals.
Orcas is a type of whale which breathe air through their lungs not gills. They can't inhale oxygen from water, it comes to the surface in order to inhale oxygen and exhale carbondioxide.
In Orca breathing is not an automatic reflex but a conscious act due to the environmental condition. When orcas come to the surface to breathe they must quickly expel the carbondioxide gas and inhale oxygen into the lungs so we can conclude that Orca breathe just like humans and other mammals.