Turning science into clinical practice – the case of carbon dioxide insufflation

Insufflation of gas (most often room air) is required during all endoscopic procedures. The volume of insufflated gas far exceeds that naturally occurring in the physiologic environment of the gastrointestinal tract. For instance, between 8 and 14 L of gas are insufflated during colonoscopy [1] [2], whereas the physiologic gas volume in the gastrointestinal tract is estimated to be only 0.1 – 1.0 L [3]. Thus, it is not surprising that many patients undergoing endoscopy experience considerable discomfort due to retained gas in the gastrointestinal tract.

In 1986, Christopher Williams asked ”Who’s for CO₂?” [4]. His commentary in Gastrointestinal Endoscopy made the case for the use of carbon dioxide (CO₂) instead of air during gastrointestinal endoscopy in order to reduce abdominal pain and discomfort (CO₂ is rapidly absorbed from the gastrointestinal tract, air is not). At that time, there was a lack of scientific evidence to support the superiority of CO₂ compared with air. Thus, it may not have been surprising that only very few endoscopists picked up William’s proposal to switch from air to CO₂.

Today however, 25 years later, CO₂ insufflation is one of the most thoroughly investigated technologies in the field of gastrointestinal endoscopy. Its performance has been tested in numerous well-designed, industry-independent randomized controlled trials, performed at a large number of different centers and countries, employing a wide range of different clinical settings.

The main advantages of CO₂ compared with air insufflation in gastrointestinal endoscopy are as follows:

Less pain and discomfort after the examination. The ability of CO2 to reduce postprocedural pain and discomfort has been shown in a large number of randomized trials in colonoscopy, flexible sigmoidoscopy, double-balloon enteroscopy, and endoscopic retrograde cholangiopancreatography (ERCP) 5 6 7 8 9 10 11 12 13 14. Elimination of the risk of explosion during interventions in the colon using electrocautery. There is a small, but not neglectable, risk of combustion during electrocautery in the colon. This risk is eliminated when using CO2 as the insufflation gas rather than air. Greater small-bowel intubation depth during enteroscopy. CO2 may enhance the yield of small-bowel endoscopy due to larger intubation depths. Possibility of immediate computed tomography colonography or other radiology/ultrasound procedures after gastrointestinal endoscopy. Possibility of intraoperative endoscopy during laparoscopy.

In this issue of Endoscopy, Suzuki and co-workers add interesting features to our knowledge of physiology, gas exchange, and acid-base metabolism during gastrointestinal endoscopy [15]. Their study was a joint venture between gastroenterologists and anesthesiologists, and an excellent example of the value of cooperation between different medical specialties. The establishment of a series of patients examined under general anesthesia with fixed ventilator settings enabled the researchers to distinguish the effect of CO₂ insufflation from other confounding factors such as hyperventilation and distress due to pain and discomfort, effects of sedatives, and changing patterns of assisted ventilation. The main message of the paper is that CO₂ insufflation is safe in endoscopy, even in long-lasting and complex procedures such as endoscopic mucosal resection and endoscopic submucosal dissection. Although arterial pressure of CO₂ (PaCO₂) and end-tidal CO₂ increased in many patients examined using CO₂ insufflation, CO₂ values were within the physiologic range in most patients, and clinically relevant hypercapnia or serious acid-base disturbances were not observed. Furthermore, the study demonstrates that patients with impaired lung function are more prone to rises in CO₂ compared with patients with normal respiratory capacity. Finally, the study proves that end-tidal CO₂ (which can be measured noninvasively) is a valid surrogate for PaCO₂ (which is invasive and requires blood sampling).

Despite the overwhelming evidence of the effectiveness and the proven lack of serious side effects, CO₂ is still only used by a small minority of endoscopy units around the world. This striking lack of transfer of scientifically proven knowledge into everyday clinical practice, as illustrated by the case of CO₂ insufflation, is of concern for the gastroenterology community. The reasons for the nonadherence to scientific evidence are difficult to determine in detail. Several factors may play a role. First, CO₂ insufflation requires extra equipment that has to be purchased, in contrast to room air, which is ubiquitous and free. However, the initial investments for CO₂ equipment (insufflator, water bottle, and tubes) are much less than the cost of a single endoscope. Secondly, CO₂ insufflation demands CO₂ containers that have to be changed regularly. However, most hospitals already have established systems for CO₂ containers, as they are used every day in operating rooms and other medical facilities. It should thus be very easy to organize supply and maintenance for endoscopy units.

Finally and importantly, CO₂ insufflation is not universally adopted because it is not promoted by the endoscopy manufacturing industry. Only a minority of endoscopy companies make CO₂ insufflators and equipment, and even fewer actively promote these products. The reasons for this are unclear, but may be due more to marketing strategy than medical demand.

Air insufflation is a major cause of abdominal pain and discomfort and is associated with rare but serious complications such as combustion and embolism, as discussed by Suzuki et al. [15]. Thus, air insufflation may be regarded as medical malpractice. There is no reason to continue to use air for insufflation, and it’s use should be discouraged. The widespread implementation of CO₂ insufflation during gastrointestinal endoscopy is overdue. The gastroenterological community should emphasize its use in clinical guidelines and push the industry to supply and market the equipment needed for it’s implementation. An important step in the right direction is the inclusion of a recommendation for CO₂ insufflation for colonoscopy in the upcoming First European guidelines on screening for colorectal cancer.

Competing interests: Dr Bretthauer has been the primary investigator (or co-investigator) for several randomized trials on CO₂ insufflation in endoscopy. Some of the studies have received equipment free of charge from manufacturers of CO₂ equipment (Olympus and Bracco Diagnostics).

References

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