Respiratory arrest is the cessation of breathing due to failure of the lungs to function effectively. Apnea is the stopping of breathing. Prolonged apnea refers to a patient who has stopped breathing for a long period of time. If the heart muscle contraction is intact, the condition is known as respiratory arrest. Lack of oxygen to the brain causes loss of consciousness. Brain injury is likely if respiratory arrest goes untreated for more than three minutes, and death is almost certain if left untreated for more than five minutes.