Capnographic Monitoring in Gastrointestinal Endoscopy for Elderly Patients

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