Though Giffords had been breathing on her own since she was shot in the head Jan. 8, doctors had left the breathing tube in as a precaution. A feeding tube was also put in to provide nutrition. Those procedures are not out of the ordinary for brain-injured patients.
Giffords' doctors have said they should be able to evaluate her ability to speak once the breathing tube is out.
Giffords, who was wounded in last weekend's attack that killed six people, remains in critical condition at University Medical Center.
"Her recovery continues as planned," the hospital said in a statement.
Her husband, astronaut Mark Kelly, has remained by her bedside.
One patient was discharged Saturday while two others remain in good condition