Inclusion Criteria:  Male and female patients aged 18 to 80 years with ASA physical status I to III scheduled for elective surgery with planned arterial catheter placement before induction of general anesthesia.  Exclusion Criteria:  Age <18 years Inability to give primary consent Pregnancy History of chronic obstructive pulmonary disease (COPD) History of asthma Suspected difficult intubation Preoperative hemoglobin less than 10 mg/dl.