its inability to support combustion, in contrast to RA in which the O2 content allows such ... but also for double-contr
Whitepaper
Insufflation Agents for Endoscopy: Carbon Dioxide versus Room Air
By Lawrence J. Brandt, MD. MACG, AGA-F, FASGE, FACP, FAACH Professor of Medicine and Surgery, Albery Einstein College of Medicine Chief, Division of Gastroenterology Montefiore Medical Center
Purpose: To determine if carbon dioxide (CO2) is a better alternative to room air (RA) for colonic insufflation due to its rapid absorption, vasodilating effects and lack of combustibility. Background: Dr. Brandt and colleagues were interested in the rapid absorption and clearance of CO2, particularly for use in patients with suspected colon ischemia who were to be colonoscoped. They posited that diminishing the duration of colon distention might help minimize reductions in colon blood flow resulting from the distention. The known vasodilating effect of CO2 in many vascular beds provided an additional incentive for the group to study the response of colon blood flow to intraluminal insufflation with CO2. Materials and Methods: Inferior mesenteric artery blood flow in greyhound dogs was measured before, during and after insufflation of the colon with RA and CO2 under conditions of transient and constant elevations of intraluminal pressures. In addition to our own research, we reviewed other published studies comparing CO2 insufflation with that of RA. Conclusion: In our study, intraluminal pressures remained elevated for briefer periods after CO2 administration, and blood flow was far less compromised, than with RA. Based upon these results and the evaluation of several other published studies comparing CO2 with RA, we concluded that CO2 is the preferred agent for colonic insufflation. In addition, an automated insufflation system has several advantages over a manual technique and should be the preferred method of administration.
Introduction Most physicians do not critically evaluate their use of RA to insufflate the GI tract during endoscopic procedures yet, many of them have also been faced with a patient who after endoscopy (usually colonoscopy) complains of abdominal pain and distention, sometimes for days after the procedure. CO2 is an attractive alternative insufflation agent compared with RA because its rapid absorption leads to a more comfortable recovery. Room air is a mixture of gases (78% nitrogen, 20% oxygen, and trace amounts of other gases). The presence of oxygen makes it potentially explosive. Use of CO2 as an insufflating agent was first suggested to minimize the risk of explosion with electrosurgical polypectomy.1 Colonic explosions, although rare, are still reported and recently have been documented during argon plasma coagulation of adenomas and radiation proctitis.2 The greater safety of CO2 is based primarily upon its inability to support combustion, in contrast to RA in which the O2 content allows such a reaction. But, CO2 also serves to reduce the concentrations of the other bacterially-derived combustible gases in the lower bowel, including hydrogen, methane, ammonia and hydrogen sulfide, which might accompany poor preparation for the procedure. The presence of any stool in the colon, including stool in the right colon when electrical current is used in the left colon or rectum, constitutes a potential danger for explosion.2
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Blood flow (% of control)
Carbon dioxide is absorbed 150x faster than nitrogen and is promptly eliminated via the lungs.3 It, therefore, results in a more comfortable examination and its use has been recommended not only for colonoscopy but also for double-contrast barium enema examinations.4-5 In 1984, Hussein and colleagues reported that with CO2 insufflation during colonoscopy, there was no significant residual gas on plain films taken 30 minutes after the procedure. In contrast, patients examined after RA insufflation showed excessive distention of the small and large bowel.4 It is surprising how much gas actually is instilled into the colon during colonoscopy. In a study by Bretthauer et al, insufflation of ~8.2 liters with a range of 1.2-19.8 liters was documented during routine colonoscopy.6
Arterio-venous oxygen difference (vol %)
Advantages of Carbon Dioxide
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Figure 1. Effects of bowel distention on blood flow and on arterio-venous difference of intestinal blood.7
Another advantage of the rapid absorption of CO2 is the lack of need to aspirate gas upon withdrawal. This may result in a decrease in miss-rate of polyps that otherwise might have been obscured behind a collapsed fold.
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Figure 2. Simultaneous display of inferior mesenteric artery blood flow and colonic intraluminal pressure following transient elevation of pressure to 35 mmHg with room air. Intraluminal pressures remain above baseline, and blood flow is reduced for the entire period of observation.11 140
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In, our study, inferior mesenteric artery blood flow in greyhound dogs was measured before, during and after insufflation of the colon with RA and CO2 under conditions of transient and constant elevations of intraluminal pressures.11 Intraluminal pressures remained elevated for briefer periods after CO2 administration and blood flow was far less compromised than with RA. Baseline pressure was reached >30 minutes after transient elevation of intraluminal pressure to 35 mmHg with RA, and blood flow was reduced for the entire period of observation (Figure 2). When CO2 was used to reach the same levels of intraluminal pressure, blood flow was increased above control values and baseline pressure was attained in 30 mmHg diminished intestine/colon blood flow (Figure 1), and it was known that such intraluminal pressures may be generated during colonoscopy.7-8 The known vasodilating effect of CO2 in many vascular beds provided an additional incentive for the group to study the response of colon blood flow to intraluminal insufflation with this agent.9-10
Blood Flow (Percent of Control)
Study Results: Carbon Dioxide vs. Room Air
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Figure 3. Simultaneous display of inferior mesenteric artery blood flow and colonic intraluminal pressure following transient elevation of pressure to 35 mmHg with CO2 Intraluminal pressures rapidly return to baseling, and blood flow is increased above control values.11
CO2 also shifts the oxyhemoglobin dissociation curve to yield a higher pO2 for any given fractional saturation.12 Such rheologic benefits of CO2 are especially important when colonoscoping anyone with colon ischemia and may be of great value in older patients predisposed to colonicischemia.
Carbon Dioxide Administration Carbon dioxide itself is fairly inexpensive. A 1350-liter tank costs about $10-20 and can be used for ~675 minutes of procedure time. There are two methods of insufflation; manual and automated. The manual method involves using a simple regulatory connection at a minimal cost. Some disadvantages to this method are that the system must be assembled on site, requires close monitoring and lacks certain safety and gas-saving features. In addition, pressures must be set by hand. The CO2EFFICIENT® endoscopic insufflator is a fully automated system that offers several advantages over manual insufflation. Carbon dioxide volumes are digitally displayed. The system features two flow modes and redundant pressure relief valves to protect against overinflation. In our experience, the CO2EFFICIENT insufflator is simple to use and potentially safer than the manual system.
Conclusion Carbon dioxide offers several advantages over room air, including; lack of combustibility, rapid absorption and vasodilating effects. These benefits help to ensure a more comfortable examination for the patient. Because CO2 is rapidly absorbed, there is no need to aspirate gas upon withdrawal. The CO2EFFICIENT® endoscopic insufflator is a fully automated system that has benefits over a manual system due to its many safety features and ease-of-use.
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Figure 4. Inferior mesenteric blood flow at a constant intraluminal pressure of 65 mmHg maintained with CO2 and 68% of control values with room air.11
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Figure 5. Observations on post-colonoscopy abdominal pain showed that 1 hour after colonoscopy, most patients insufflated with room air had significant residual gas. Data from this study showed that 94% of patients insufflated with CO2 had only trace to minimal gas.13
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End-tidal CO2 (kPa)
In a study by Bretthauer et al, no rise in end-tidal pCO2, a non-invasive parameter of arterial pCO2, was observed in routinely unsedated patients who were given CO2, although patients with severe heart or lung disease were excluded from the study (Figure 6).14 Patients in the CO2 group also had significantly less pain for up to 6 hours after the procedure, as evaluated by a visual analog scale (Figure 7). In a followup study, Bretthauer and colleagues showed that CO2 insufflation is also safe in sedated patients without significant difference between patients in whom RA or CO2 was used.15
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Figure 6. End-tidal CO2 before and after colonoscopy.14 35
Mean VAS score (mm)
In a study by Sumanac and colleagues, using a commercially available CO2 delivery system, the effects of CO2 and RA insufflation on residual bowel gas and post-procedural pain were compared in 97 patients (Figure 5).13 Both parameters were less in the CO2 group at 1 and 6 hours. Seventy-one percent of patients given RA had colon distention >6 cm compared with only 4% in the CO2 group. Ninety-four percent of patients insufflated with CO2 had minimal residual gas compared with 2% in subjects given RA. Of patients insufflated with RA, 45% and 31% had pain at 1 and 6 hours respectively, whereas 7% and 9% of those in whom CO2 was used had pain at the same time periods.
Blood Flow (Percent of Control)
Literature Review
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Figure 7. Plain scores before and after colonoscopy.14
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References: 1. Rogers BHG. Gastrointest Endos 1974; 20:115-117. 2. Ben-Sousson E, et al. Eur J Gastroenterol Hepatol 2004; 12:1315-1318. 3. Grant DS, Bartram CI. Brit J Radiol 1966; 59:190-191. 4. Hussein AMJ, et al. Gastrointest Endos 1984; 30:68-70. 5. Coblentz C, et al. Clin Invest Med 1985; 8:A101. 6. Bretthauer M, et al. Gastrointest Endos 2003; 58(2):203-206. 7. Boley SJ, et al. Am J Surg 1969; 117:228-234. 8. Kozarek RA, et al. Gastroenterol 1980; 78:7-14. 9. Daugherty RM Jr, et al. Am J Physiol 1967; 213:1102-1110. 10. Sidky MS, Bean JW. Am J Physiol 1951; 167:413-425. 11. Brandt LJ, et al. Gastrointest Endos 1986; 32:324-329. 12. Duling BR. Circ Res 1973; 32:370-376. 13. Sumanac K, et al. Gastrointest Endos 2002; 56:190-194. 14. Bretthauer M, et al. Gut 2002; 50:604-607. 15. Bretthauer M, et al. Endoscopy 2005; 37:706-709.
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