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No Trace, Wrong Place

During cardiac arrest and CPR, capnogram is attenuated. In oesophageal intubation, capnogram is a flat line. Watch Professor Tim Cook explain more.

The Royal College of Anaesthetists (RCoA) and the Difficult Airway Society (DAS) have created this video “Capnography: No Trace = Wrong Place”, presented by Professor Tim Cook. It has a very important message: during cardiac arrest a completely flat capnograh trace means oesophogeal intubation until proven otherwise.

In the previous step, we learnt that failure to interpret a capnogram correctly, led to oesophageal intubations going unrecognised and contributed to severe patient harm and death. Following NAP4, the President of the RCoA wrote to all Trust CEOs reinforcing several recommendations, including that all patients ventilated in theatre, the ICU or ED should be monitored with continuous capnography.

Capnography is the visual display, or waveform, of the partial pressure or concentration of carbon dioxide (CO2) in inspired and expired gases, plotted against time, and it shows characteristic patterns during the respiratory cycle. The waveform provides important information, including confirmation that the airway is ‘open’ and that artificial airway devices such as tracheal tubes, supraglottic airway devices or tracheostomies are in the correct place [1]. For a simple visual guide we recommend you review and share this ‘Hats and Caps’ infographic.

The use and correct interpretation of capnography improves patient safety in all areas where artificial airways are used, including anaesthetic rooms and theatres, recovery areas, the emergency department, critical care units and during transfers.

A flat capnograph trace means there is no ventilation of the lungs: the tube is either not in the trachea or the airway is completely obstructed.

Capnography during Cardiac Arrest

During cardiac arrest, ventilation with or without chest compressions leads to an attenuated but visible expired CO2 trace, as demonstrated in this video and shown in the illustration below.

Good quality chest compressions will minimise the degree of attenuation by optimising the cardiac output and is a good measure of chest compression effectiveness. A sharp rise in expired CO2 trace is an adequate ”sign of life” to stop chest compressions and perform a pulse check.

attenuated capnography trace Attenuated capnography trace during cardiac arrest

The Global Capnography Project

The Lancet Commission on Global Surgery emphasised the importance of access to safe anaesthesia care. Capnography is an essential monitor for safe anaesthesia but is not yet universally available. The Global Capnography Project (GCAP), which started in 2016, aims to introduce capnography to low-income countries. This international project aims to make global capnography become the standard of care, like pulse oximetry, to improve patient safety worldwide [2]. In Week 5 of this course we’ll learn about airway management in Low and Middle Income Countries, and look at airway management from a Global Perspective.

After watching the video, please join the discussion and share your experience of using capnography in your workplace. Is waveform capnography available wherever you need it? What other useful information can capnography provide?

In the “Downloads” and “See Also” section below you will find a number of resources on capnography that may help you answer this question.

In the first part of this course we have explored some of the key concepts of safe airway management. But is there more to airway safety? In the next activity, we will explore the role of Human Factors and Ergonomics, beginning with the case of Mrs Elaine Bromiley, who tragically died as a result of failed airway management.


  1. T. M. Cook F. E. Kelly A. Goswami. Hats and caps’ capnography training on intensive care. Aanesthesia. March 2013
  2. Jooste R, Roberts F, Mndolo S, Mabedi D, Chikumbanje S, Whitaker DK, O’Sullivan EP. Global Capnography Project (GCAP): implementation of capnography in Malawi – an international anaesthesia quality improvement project. Anaesthesia. 2019 Feb;74(2):158-166. doi: 10.1111/anae.14426. Epub 2018 Sep 25
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