Carbon dioxide insufflation for endoscopic retrograde cholangiopancreatography: A meta-analysis and systematic review

Table 2 Study characteristics

Author	Year	Country	Study design	Participants	Participants (CO2/Air)	Mean age (CO2/Air)
Bretthauer et al[8]	2007	Norway	Multi-centers	Low risk	118 (58/58)	57/54
Maple et al[12]	2009	United States	Single-center	Low risk	105 (50/50)	57/51.7
Dellon et al[9]	2010	United States	Single-center	High risk and low risk	78 (36/38)	60.1/59.7
Kuwatani et al[10]	2011	Japan	Multi-centers	Low risk	80 (40/40)	66.1/68.7
Luigiano et al[11]	2011	Italy	Single-center	Low risk	78 (39/37)	66.1/67.1
Mei et al[13]	2011	Australia	Single-center	Not mentioned	61 (34/27)	Not mentioned
Arjunan et al[14]	2011	India	Single-center	Low risk	298 (147/151)	Not mentioned

Low risk refers to patients without chronic obstructive pulmonary diseases; high risk refers to patients with chronic obstructive pulmonary diseases.