Methods: Electronic databases were accessed selecting only randomized controlled trials comparing insufflation with CO2 and ambient air in colonoscopy. The evaluated outcomes were pain, abdominal distension and flatulence, cecal intubation rate, cecal intubation and total procedure time, volume of gas, CO2 measurement, and need of sedation or analgesia, and polyp detection rate.
Results: Thirty randomized controlled trials were selected (4854 patients). Meta-analysis showed reduction in pain risk in the CO2 group immediately after the colonoscopy (Risk difference-RD 0.11[0.03, 0.19]), 1h (RD 0.29 [0.24, 0.34]), 3h (RD 0.22[0.11, 0.34]) and 6h (RD 0.21 [0.17, 0.26]) after colonoscopy. The reduction of flatulence risk 1h and 6h after the procedure was greater in CO2 group (RD 0.54 [0.43, 0.66] and RD 0.65[0.38,0.92], respectively). There were no significant differences between the two groups regarding pain during the procedure, pain and flatulence 24h after colonoscopy, abdominal bloating, request for medication, safety, gas volume, polyp detection rate, cecal intubation rate, time to cecum and total procedure time.
Conclusions: CO2 insufflation improves tolerance to colonoscopy, reducing pain and flatulence out to 6 hours following the procedure.
Keywords: Air; Carbon dioxide; Colonoscopy; Insufflations; Pain
However, because of the necessity of gas insufflation for the adequate visualization of the colonic mucosa, patients usually complain about pain and abdominal discomfort during and after the procedure associated mainly with the use of ambient air, which stays in the intestine for a longer period [4] due to the presence of nitrogen gas. To increase the tolerance and the disposition to repeat the examination, the insufflation of carbon dioxide (CO2) is increasingly utilized. CO2 is rapidly absorbed by the intestinal mucosa and subsequently eliminated by breath, which may lead to less pain, flatulence and distension related to the procedure [5-8]. Comparative analyses between the use of CO2 and ambient air in colonoscopy were shown in two meta-analyses published previously [9,10].
The objective of this systematic review and metaanalysis is to update this knowledge through new studies comparing which insufflation method is related to less unpleasant symptoms, faster and safer examinations, and to add outcomes that were not yet described in the literature.
1- Study design: RCT.
2- Population: patients subjected to colonoscopy.
3- Intervention: intestinal insufflation with CO2.
4- Comparison: intestinal insufflation with ambient air
5- Outcomes: the evaluated outcomes were pain, abdominal distension and flatulence related to colonoscopy, cecal intubation rate, cecal intubation time and total procedure time, volume of gas used, CO2 measurement at the end of the procedure, need of sedation or analgesia, and polyp detection rate.
Study |
Population (N) |
Co2 (N) |
Air (N) |
Follow Up |
Randomization |
Blinding |
Losses |
Power Calculation |
ITT |
Prognostic |
Outcomes |
Jadad Score |
Amato et al. 2013 [13 ] |
228 |
115 |
113 |
24 hours |
YES+ |
Only patient |
NO |
YES |
YES |
YES |
YES |
2 |
Bretthauer et al. 2002 [14 ] |
240 |
121 |
119 |
24 hours |
YES? |
Patient and endoscopists |
YES |
YES |
NO |
YES |
YES |
4 |
Bretthauer et al. 2003 [15 ] |
218 |
109 |
109 |
24 hours |
YES? |
Patient and endoscopists |
YES |
NO |
NO |
YES |
YES |
4 |
Bretthauer et al. 2005 [16 ] |
103 |
52 |
51 |
24 hours |
YES? |
Patient and endoscopists |
YES |
NO |
NO |
? |
YES |
4 |
Calderon et al. 2012 [4 ] |
214 |
132 |
82 |
2 hours |
Yes? |
Nurse |
NO |
NO |
NO |
YES |
YES |
1 |
Chao et al. 2010 [17 ] |
104 |
46 |
58 |
During colonoscopy |
Yes? |
Patient and anesthesiologist |
NO |
NO |
NO |
YES |
YES |
3 |
Chen et al. 2013 [18] |
193 |
96 |
97 |
24hours |
YES+ |
Patient, endoscopist, research staff |
YES |
YES |
YES |
YES |
YES |
5 |
Chen et al. 2014 [19 ] |
98 |
51 |
47 |
Until discharge |
YES+ |
Patient and endoscopists |
YES |
NO |
NO |
YES |
YES |
5 |
Chen et al. 2016 [20 ] |
125 |
63 |
62 |
24h |
YES+ |
Patient , endoscopists, anesthesiologist, study assistant |
YES |
YES |
YES |
YES |
YES |
5 |
Church et al. 2003 [21] |
247 |
123 |
124 |
1h |
Yes - |
Only patient |
NO |
NO |
NO |
YES |
YES |
1 |
Cleland et al. 2013 [22] |
205 |
108 |
97 |
1h |
Yes? |
Patient, endoscopist, nurse care |
NO |
YES |
NO |
YES |
YES |
3 |
Diez-Redondo et al. 2012 [23] |
270 |
129 |
141 |
24 hours |
Yes + |
Patient, endoscopist, nurse care |
YES |
YES |
NO |
YES |
YES |
4 |
Geyer et al. 2011 [24 ] |
219 |
110 |
109 |
24 hours |
Yes - |
Patient, endoscopist |
NO |
YES |
NO |
NO |
YES |
3 |
Hsu et al. 2012 [25] |
100 |
67 |
33 |
1 hour |
Yes ? |
Only patient |
YES |
NO |
NO |
YES |
YES |
2 |
Hsu et al. 2014 [26] |
120 |
60 |
60 |
2 hours |
Yes+ |
Patient, endoscopist, assistant nurses, nurses recovery room |
NO |
YES |
NO |
YES |
YES |
4 |
Imai et al. 2012 [27] |
37 |
19 |
18 |
24 hours |
Yes+ |
Patient, endoscopist |
YES |
YES |
NO |
YES |
YES |
5 |
Landaeta et al. 2014 [28] |
63 |
30 |
33 |
24h |
Yes? |
Not informed |
YES |
NO |
NO |
YES |
YES |
2 |
Liu et al.2009 [29] |
349 |
174 |
175 |
24h |
Yes - |
Single blinded |
NO |
NO |
NO |
YES |
YES |
1 |
Lynch et al. 2015 [30] |
191 |
97 |
94 |
Until discharge |
Yes + |
Patient, endoscopist, nurse staff |
YES |
YES |
NO |
YES |
YES |
5 |
Mayr et al. 2012[31] |
156 |
77 |
79 |
24h |
Yes + |
Patient, endoscopist |
YES |
YES |
NO |
YES |
YES |
5 |
Murakami et al. 2016 [32] |
158 |
75 |
83 |
4h |
Yes - |
Only patient |
YES |
YES |
NO |
YES |
YES |
2 |
Riss et al. 2009 [33] |
300 |
157 |
143 |
12h |
Yes + |
Only patient |
YES |
YES |
YES |
YES |
YES |
3 |
Seo et al. 2013 [34] |
94 |
48 |
46 |
24h |
Yes + |
Patient, endoscopist, nurses recovery room |
YES |
YES |
YES |
YES |
YES |
5 |
Singh et al. 2012 [35] |
142 |
70 |
72 |
Until discharge(~3) |
Yes ? |
Patient, endoscopist, nurse |
NO |
NO |
NO |
NO |
YES |
3 |
Stevenson et al. 1992 [36] |
56 |
27 |
29 |
24h |
Yes + |
Patient, endoscopist |
NO |
NO |
NO |
? |
YES |
4 |
Sumanac et al. 2002 [37] |
97 |
46 |
51 |
24h |
Yes + |
Patient, endoscopist |
YES |
NO |
YES |
YES |
YES |
5 |
Szura et al.2015[38] |
200 |
100 |
100 |
1h |
Yes + |
Only patient |
YES |
YES |
YES |
YES |
YES |
3 |
Uraoka et al. 2009 [39] |
114 |
57 |
57 |
6h |
Yes + |
Patient, endoscopist |
YES |
YES |
YES |
YES |
YES |
5 |
Wong et al. 2008 [40] |
93 |
44 |
49 |
2h |
Yes ? |
Patient, endoscopist, assessor |
YES |
YES |
NO |
YES |
YES |
4 |
Yamano et al. 2010 [41] |
120 |
66 |
54 |
24h |
Yes ? |
Patient, endoscopist |
YES |
NO |
NO |
YES |
YES |
4 |