The purpose of this study is to assess the differences of safety and efficacy of carbon dioxide insufflation instead of air during sedated or unsedated endoscopy.

Total 640 participants who are indicated to accept endoscopic examinations or procedures will be enrolled in this study. The participants will be divided into 2 groups according to the examination field, esophagogastroduodenoscopy group (320 participants) and colonoscope group (320 participants). The participants in each group will be divided into sedated endoscope subgroup and sedated and unsedated endoscope subgroup (each subgroup is inclusive of 160 participants). Carbon dioxide (CO2) or room air will be used randomly to insufflate the bowel lumen during the procedure in each subgroup.

Inclusion Criteria:

• outpatients referred for panendoscopy or colonoscopy examination

Exclusion Criteria:

• pregnancy, breast feeding, severe chronic obstructive lung disease or severe heart failure, renal function impairment, inability to understand participant information, a history of abdominal surgery, or refusal to participate in this study