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Bhavani Shankar Kodali MD


The role of capnography in ICU and Emergency Department

July Issue of Anaesthesia has an editorial titled "Time for capnography everywhere". This is a must read article summarizing the value of capnography outside of operating rooms. It is 66 times more likely to have airway related deaths in ICU because of not using capnography routinely, unlike in the operating rooms. Capnography could have prevented 74% of them. Anaesthesia 2011;66:544-9. This article also summarizes the findings of National Audit Project 4  of Association of Anaesthetists of  Great Britain and Ireland. 

In the May 2011 issue of British Journal of Anesthesia, there are two important papers highlighting the complication of airway management during anesthesia as well as in emergency and intensive care units (ICU, ED). The special articles  relate to the fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society (Cook TM, Woodall N, Frerk C. British Journal of Anaesthesia 2011;106(5):617-31 and Cook TM, Woodall N, Harper J, Benger J. British Journal of Anaesthesia 2011;106(5):632-42). This is also accompanied by an editorial (Norris AM, Hardman JG, Asai T. British Journal of Anaesthesia 2011;106(5):613-6).

The first paper analyzed the data of major airway management complications during general anesthesia (death, brain damage, emergency surgical airway, unanticipated intensive care unit admission) from all National Health Service hospitals for 1 yr. The data reveals that only 25% of relevant airway incidents are generally reported and the actual incidence could be higher. There is also evidence that there is a room for substantial improvement in airway management. 

The second article relates to a study designed to identify and study serious airway complications occurring anesthesia, in intensive care and the emergency department. Reports of major complications of airway management (death, brain damage, emergency surgical airway, unanticipated ICU admissions, prolonged ICU stay) were collected from all National Health Service Hospitals over a period of 1 yr. A total of 184 events met the inclusion criteria: 36 in ICU and 15 in ED. In ICU, 61% of events led to death or persistent neurological injury, and 31% in the ED. Airway events in ICU and the ED were more likely than those during anesthesia. The complications occurred during out-of-hours, and managed by doctors  with less anesthetic experience and lead to permanent harm. Failure to use capnography contributed to 74% of cases of death or persistent neurological injury. The authors concluded that one in four major airway events in a hospital are likely to occur in ICU or the ED. Analysis of the cases has identified repeated gaps in care that include poor identification of at-risk patients, poor or incomplete planning, inadequate provision of skilled staff and equipment to manage these events successfully, delayed recognition of events, and failed rescue due to lack of or failure of interpretation of capnography. The project findings suggest avoidable deaths due to airway complications occur in ICU and the ED.

The above highlighted conclusions reinforces once again what anesthesiologists concluded in United States more than two and half decades ago that use of Capnography and pulse Oxymetry could have prevented 93% % of airway complications during anesthesia. This eventually led to development of ASA standards of monitoring publicizing the benefits of Oxymetry and capnography during anesthesia.

The data from these current studies will eventually promote increasing use of capnography in ICU's ED's and subsequently may become  mandatory in all ventilated patients, and during airway management.

Specific recommendations highlighted pertaining to capnography are:

ICU settings:

  • Capnography should be used for intubation of all critically ill patients irrespective of location
  • Continuous capnography should be used in ICU patients with tracheal tubes (including tracheostomy) who are intubated and ventilator dependent. Cost and technical difficulties may be practical impediments to the rapid introduction of routine capnography. However, these need not prevent implementation.
  • Where capnography is not used, the clinical reason for not using it should be documented and reviewed regularly.
  • Training of all clinical staff who work in ICU should include interpretation of capnography. Teaching should focus on identification of airway obstruction or displacement. In addition, recognition of the abnormal (but not flat) capnography tracing during CPR should be emphasized.  

Anesthesia and Post anesthesia care recovery units:

Capnography was used in all anesthetic cases. In contrast to cases reported from ICU and emergency departments, capnography appeared to be used universally for intubation and in the operating room. Reviewers judged that the use of capnography would have led to earlier identification of airway obstruction in several cases. There were three anesthesia related cases, including two deaths in which optimal interpretation of capnography might have altered the clinical course. In one case, prolonged airway obstruction in recovery due to aspirated blood clot was diagnosed as asthma for an extended period. (t was not stated if capnography was used). In the second case, laryngeal mask misplacement in an ASA II patient led to severe hypoxia; intubation was performed while patient was peri-arrest. Intubation was difficult, as was ventilation and the capnograph showed 'minimal CO2'. Capnography was ''flat' during prolonged cardiac arrest and this appeared to be a case of unrecognized esophageal intubation. In the third case, a healthy patient was intubated and transferred into operating room but became hypoxic with a flat capnography trace. Anaphylaxis was suspected but senior anesthesiologist help promptly diagnosed the tracheal tube in the esophagus.: the patient was transferred to ICU and made a full recovery. In summary, there were three cases of unrecognized esophageal intubation during anesthesia leading to one death and one case of brain damage.

Take home message
Use capnography in ED, ICU, and PACU.
Be knowledgeable with capngraphy tracings
Use capnography during transport to detect endotracheal tube misplacements

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