Nasal Mask Kit in Gastrointestinal Endoscopy

Inclusion Criteria: * 18≤ Age ≤60 * patients undergoing combined gastroendoscopy and colonoscopy procedure * patients signed informed consent form * ASA classification I-II * Estimated procedure time \<=45min Exclusion Criteria: * Coagulation disorders or a tendency of nose bleeding * Diagnosed heart disease (heart failure, angina, myocardial infarction, arrhythmia, etc.) * Diagnosed chronic obstructive pulmonary disease or current other acute or chronic lung disease requiring supplemental chronic or intermittent oxygen therapy) * hypoxia (SpO2\< 90 % ) * Upper respiratory tract infection * increased intracranial pressure * Fever (core body temperature \>37.5 ℃) * Pregnancy, breastfeeding, or positive pregnancy test * Emergency procedure or surgery * Multiple trauma * Allergy to propofol or tape and adhesives * BMI\<18.5 or BMI\>30