Reducing the risk of confirmation bias in unrecognised oesophageal intubation

Editor—In 2012, the British Journal of Anaesthesia published a novel article examining how cognitive errors are a major cause of incorrect diagnosis and treatments in anaesthesia.¹ The authors highlighted that cognitive errors are based on inner feelings/biases, and are sentiments that that we do not readily admit to and perhaps do not recognise. Furthermore, they discussed that cognitive errors are thought-process errors, linked to failed biases or heuristics, and that ‘while heuristics serve as the foundation for all mature medical decision making, they can lead to grave errors. The doctor must be aware of which heuristics he is using’.² A heuristic can be defined as a mental shortcut that eases the cognitive load of making a decision, and should only be viewed as a ‘rule of thumb’. Heuristics and biases are frequently used in anaesthesia; they allow rapid decision making, but cognitive errors occur when these subconscious processes and mental shortcuts are relied on exclusively or under the wrong circumstances.¹

In 2016, two elective surgical patients died after unrecognised/undetected oesophageal intubations. After the inquests, both coroners independently issued Regulation 28 Reports to the relevant authorities demanding local and national action to be implemented to prevent further deaths from unrecognised oesophageal intubation.3, 4 The response of NHS England was for NHS Improvement to add undetected oesophageal intubation onto the 2018 Never Events list.⁵ Never Events are defined as ‘Serious incidents that are wholly preventable because guidance or safety recommendations that provide strong systemic protective barriers are available at a national level and should have been implemented by all healthcare providers’. However, shortly after publication, undetected oesophageal intubation was suspended from the 2018 Never Events list.⁵ The Royal College of Anaesthetists and the Difficult Airway Society launched the ‘No Trace=Wrong Place’ video resource which is essential viewing for all clinicians involved in airway management.⁶

The video emphasises the need and importance of observing a satisfactory capnograph trace in being able to confirm airway intubation, and if there is no satisfactory trace it must be assumed that the tracheal tube is in the oesophagus and that remedial actions must be immediately taken. The video also reminds the viewer of the results of the 4th National Audit Project of the Royal College of Anaesthetists.7, 8 The report was published in 2011, and identified nine episodes of prolonged oesophageal intubation, undetected oesophageal intubation, or both that caused death or severe harm and occurred during the 1 yr study period. All nine episodes were attributed to either the lack of use of capnography or misinterpretation of a flat capnography trace. The video reinforces the concept that even in cardiac arrest, carbon dioxide is detected during ventilation of the lungs. Thus, the ubiquity of the mantra ‘No Trace=Wrong Place’.

Like many catastrophes, the two catastrophes that led to the coroner's inquests had multiple contributing factors, and we postulate that confirmation bias (a type of cognitive and human error) is another one. Confirmation bias is a well described innate psychological attribute; it has been defined as ‘Seeking or acknowledging only information that confirms the desired or suspected diagnosis’,¹ and is a tendency to search for evidence that confirms rather than refutes the initial hypotheses.⁹ When applied to the cases, it would explain why, after having observed ancillary clinical signs normally associated with successful tracheal intubation, the possibility of oesophageal intubation was not excluded. It is recognised that subjective methods of confirmation of tracheal tube placement, such as observation of thoracic movement, auscultation of the chest, fogging of the tube lumen, and even perception of the tube passing through the vocal cords may all occur with oesophageal intubation.¹⁰ Thus, reliance on and use of these signs will contribute to confirmation bias.

In an attempt to overcome human errors, the Japanese rail network (which is one of the safest railway systems on the planet), devised the ‘pointing and calling’ system.¹¹ Amongst other things, the ‘pointing and calling’ safety system dictates that on successful completion of a task, the worker verbally states the task has been completed. By verbalising correct completion of the task, the cognitive control processes responsible for the supervisory attentional system that are necessary for effective retrieval and activation of working memory are reinforced. The act of verbalisation also allows the co-workers to know that the task has been satisfactorily completed. ‘Pointing and calling’ has been demonstrated to significantly reduce the rate of work-related human errors in several industries and more recently in healthcare.¹²

In summary, we agree with Stiegler and colleagues,¹ who concluded that anaesthetists must have insight into their own decision-making processes and that further research in this area is needed to reduce decision-making errors and improve patient safety across the whole of anaesthesia. In the meantime, in order to reduce the risk of confirmation bias leading to unrecognised oesophageal intubation, all healthcare workers undertaking intubation must refrain from using non-specific signs such as tube misting and chest rising, and must rely on a satisfactory capnography waveform trace. Moreover, to facilitate the activation of cognitive control processing, successful airway intubation should only be accepted after observation of a satisfactory capnography waveform trace, when accompanied by verbalisation of a statement such as ‘presence of a satisfactory capnography waveform trace’.

Declaration of interest

The authors declare that they have no conflicts of interest.