Inclusion Criteria:  65 ≤ Age <80 patients undergoing gastrointestinal endoscopes patients signed informed consent form ASA classification I-II  Exclusion Criteria:  Coagulation disorders or a tendency of nose bleeding An episode/exacerbation of congestive heart failure (CHF) that requires a change in medication, diet or hospitalization from any cause in the last 6 months Severe aortic stenosis or mitral stenosis Cardiac surgery involving thoracotomy (e.g., coronary artery bypass graft (CABG), valve replacement surgery) in the last 6 months Acute myocardial infarction in the last 6 months Acute arrhythmia (including any tachycardia - or bradycardia) with the fluid of hemodynamics instability Diagnosed chronic obstructive pulmonary disease or current other acute or chronic lung disease requiring supplemental chronic or intermittent oxygen therapy) Pre-existing bradycardia (heart rate < 50 / min), or hypoxia (SaO2< 90 % ) Need supplemental oxygen because of pre-existing diseases Emergency procedure or surgery Multiple trauma Upper respiratory tract infection Allergy to propofol or tape and adhesives