Low levels of oxygen may lead to confusion and impairment of judgement. This can render a patient incapable of making safe and reasoned decisions. In cases where the patient is unable to make sound decisions, the ambulance officers may act in the patient's best interests.
Removal of oxygen by hospital staff on arrival often occurs so that blood gas estimations may be done. This is part of hospital management and has no bearing on the need for oxygen during ambulance management.