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Is waveform capnography reliable in neonates?

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Response to Professor Cook et al.'s letter
Alexandra Scrivens, Sanja Zivanovic and Charles C Roehr
Published on: 14 October 2021
Response to Dr Whitaker's letter
Alexandra Scrivens, Sanja Zivanovic and Charles C Roehr
Published on: 20 November 2019
Waveform capnography is reliable to ensure oxygenation
David Whitaker
Published on: 20 November 2019
Prof Tim Cook
TM Cook, Katie Foy and Fiona E kelly
Published on: 12 November 2019

Published on: 14 October 2021
Response to Professor Cook et al.'s letter
- Alexandra Scrivens, Neonatal registrar Oxford University Hospitals, University of Oxford
- Other Contributors:
  Sanja Zivanovic, Paediatric clinical lecturer
  
  Charles C Roehr, Consultant neonatologist
Dear Editor,
We thank Professor Cook et al. for their letter in response to our Archimedes paper. We agree that waveform capnography may have benefit in earlier detection of oesophageal intubation or unplanned extubations in neonates, as has been assumed in adults. However, this assumption will require further study. Following an UK expert panel meeting, we are looking forward to investigating the use of waveform capnography monitoring in neonates.
As previously discussed in correspondence with Dr Whitaker, there are two pertinent questions to answer here for the neonatal population:
1) In neonates (P), does the addition of waveform capnography (I) compared to current methods of detection (colourimetric capnography, ventilator measurements, oxygen saturations and clinical examination) (C) provide an advantage in earlier detection of oesophageal intubation or unplanned extubation (O)?
2) Does the displayed numerical value in waveform capnography correlate with PaCO2 reliably enough to guide ventilator changes?
In our review, we specifically sought to address the second question. Those familiar with contemporary neonatal practice will know that many NICUs use transcutaneous capnography. Question 2 has a particular pertinence in neonates as their physiology is different from the adult and even paediatric population. Neonates are particularly prone to rapid changes in PaCO2, due to their changing lung compliance. Due to their lack of cerebral auto...
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Dear Editor,
We thank Professor Cook et al. for their letter in response to our Archimedes paper. We agree that waveform capnography may have benefit in earlier detection of oesophageal intubation or unplanned extubations in neonates, as has been assumed in adults. However, this assumption will require further study. Following an UK expert panel meeting, we are looking forward to investigating the use of waveform capnography monitoring in neonates.
As previously discussed in correspondence with Dr Whitaker, there are two pertinent questions to answer here for the neonatal population:
1) In neonates (P), does the addition of waveform capnography (I) compared to current methods of detection (colourimetric capnography, ventilator measurements, oxygen saturations and clinical examination) (C) provide an advantage in earlier detection of oesophageal intubation or unplanned extubation (O)?
2) Does the displayed numerical value in waveform capnography correlate with PaCO2 reliably enough to guide ventilator changes?
In our review, we specifically sought to address the second question. Those familiar with contemporary neonatal practice will know that many NICUs use transcutaneous capnography. Question 2 has a particular pertinence in neonates as their physiology is different from the adult and even paediatric population. Neonates are particularly prone to rapid changes in PaCO2, due to their changing lung compliance. Due to their lack of cerebral autoregulation, changes in PaCO2 have a direct effect on blood flow to and around the brain. Swings in PaCO2 are known to be associated with poorer long term outcomes, severe neurological complications including intraventricular haemorrhage and potentially death. Thus, whenever a measured value is presented, it is important that staff are trained to interpret the value in the clinical setting to adequately respond, re-evaluate and avoid mistakes.
Despite the PICNIC survey’s merits as a thorough and well carried out national survey, PICNIC was reported by the mainstream media in a manner which may cause undue distress amongst NICU parents. Therefore, we aimed to highlight this problem in our opening paragraph. Regrettably, media misinterpretation is not an infrequent issue.
We are surprised by the comment by Prof. Cook et al. that our review omits the study by Kugelman et al. Their 2016 study on the impact of continuous capnography in ventilated neonates is included, both in the table and as reference number 30 of our paper. This study involved a small number of infants, relied on parameters set by ETCO2 (which has been shown by other studies not to approximate well to PaCO2) and was clearly underpowered to detect differences in neurological outcomes between groups.
To conclude, we feel there may be a role for waveform capnography in neonatal practice providing that concerns about safety (interference with volume guarantee ventilation, auto-triggering of ventilators, etc.) can be alleviated through careful study. If proven effective, waveform capnography must be adopted together with a clear understanding of its benefits and limitations, as well as training for all medical and nursing staff to avoid harm and ensure maximum benefit to patients.
A Scrivens
S Zivanovic
CC Roehr
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Conflict of Interest:
None declared.
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Published on: 20 November 2019
Response to Dr Whitaker's letter
- Alexandra Scrivens, Paediatric registrar Newborn Care Centre, Oxford University Hospitals
- Other Contributors:
  Sanja Zivanovic, Paediatric clinical lecturer
  
  Charles C Roehr, Consultant neonatologist
Dr Whitaker, in a letter in response to our Archimedes review of whether waveform capnography reliably approximates paCO2 in neonates, highlights two important questions which capnography seeks to address: Firstly, whether or not the endotracheal tube (ETT) is patent and correctly positioned in the trachea and secondly, whether the current ventilation strategy provides optimal CO2 clearance for the patient. The two questions are, of course, interlinked.
To date, in our field of neonatal medicine, the ETCO2 provides a valuable adjunct to clinical examination in determining ETT position and patency both at the point of intubation and during ongoing mechanical ventilation. However, for reasons explained in the paper, the numerical approximations to alveolar pCO2 provided by the currently available techniques of wave form capnography in neonates are not accurate enough to guide ventilatory changes. Thus, to guide ventilator changes, many neonatal intensive care units currently use transcutaneous capnometry.
In addition to the physiological properties, the waveform capnography sensors add extra weight and dead space to an infant’s ventilator circuit. This adds further complexity, like their still not fully assessed effect on volume-guarantee ventilation and potential for auto-triggering of ventilators. As volume guarantee is now considered the gold standard for ventilating preterm infants with respiratory distress syndrome, the value of waveform capnography, in addi...
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Dr Whitaker, in a letter in response to our Archimedes review of whether waveform capnography reliably approximates paCO2 in neonates, highlights two important questions which capnography seeks to address: Firstly, whether or not the endotracheal tube (ETT) is patent and correctly positioned in the trachea and secondly, whether the current ventilation strategy provides optimal CO2 clearance for the patient. The two questions are, of course, interlinked.
To date, in our field of neonatal medicine, the ETCO2 provides a valuable adjunct to clinical examination in determining ETT position and patency both at the point of intubation and during ongoing mechanical ventilation. However, for reasons explained in the paper, the numerical approximations to alveolar pCO2 provided by the currently available techniques of wave form capnography in neonates are not accurate enough to guide ventilatory changes. Thus, to guide ventilator changes, many neonatal intensive care units currently use transcutaneous capnometry.
In addition to the physiological properties, the waveform capnography sensors add extra weight and dead space to an infant’s ventilator circuit. This adds further complexity, like their still not fully assessed effect on volume-guarantee ventilation and potential for auto-triggering of ventilators. As volume guarantee is now considered the gold standard for ventilating preterm infants with respiratory distress syndrome, the value of waveform capnography, in addition to standard expiratory tidal volume monitoring on volume-guarantee ventilated infants and transcutaneous capnometry, is a topic worthy of further research and discussion.
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Conflict of Interest:
None declared.
- Back to top
Published on: 20 November 2019
Waveform capnography is reliable to ensure oxygenation
- David Whitaker, Consultant in Anaesthesia and Intensive Care Manchester Royal Infirmary
I was interested to read the Archimedes article reviewing the structured question ‘in neonates who require ventilation, does waveform capnography give an accurate approximation of PaCO2?’ The findings such as the accuracy of ETCO2 decreases with the severity of lung disease (Grade B) adds to similar knowledge about waveform capnography when it was introduced in adults.

Whenever capnography is discussed however it should always be remembered that the primary reason for its introduction into clinical practice was to reliably ensure patients oxygenation and reduce the incidence of hypoxic brain damage, which it did so dramatically. The presence of a capnography waveform is the gold standard to demonstrate the integrity and correct position of an airway and establish that the patient is being ventilated with the intended oxygen. This eureka moment discovering that waveform capnography is more about oxygenation than accuracy of PaCO2 estimation is crucial for patient safety. The exact value of PaCO2 is secondary.

Unfortunately for over 20 years adult intensive care missed this eureka moment and consequently never started to use waveform capnography in adult ITUs when it was being universally introduced into operating theatres in the late 1980s [1].

Despite waveform capnography continuing to save many patients lives in operating theatres the argument that the accuracy of ETCO2 decreased with the severity of lung disease predominated in intensive care and w...
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I was interested to read the Archimedes article reviewing the structured question ‘in neonates who require ventilation, does waveform capnography give an accurate approximation of PaCO2?’ The findings such as the accuracy of ETCO2 decreases with the severity of lung disease (Grade B) adds to similar knowledge about waveform capnography when it was introduced in adults.

Whenever capnography is discussed however it should always be remembered that the primary reason for its introduction into clinical practice was to reliably ensure patients oxygenation and reduce the incidence of hypoxic brain damage, which it did so dramatically. The presence of a capnography waveform is the gold standard to demonstrate the integrity and correct position of an airway and establish that the patient is being ventilated with the intended oxygen. This eureka moment discovering that waveform capnography is more about oxygenation than accuracy of PaCO2 estimation is crucial for patient safety. The exact value of PaCO2 is secondary.

Unfortunately for over 20 years adult intensive care missed this eureka moment and consequently never started to use waveform capnography in adult ITUs when it was being universally introduced into operating theatres in the late 1980s [1].

Despite waveform capnography continuing to save many patients lives in operating theatres the argument that the accuracy of ETCO2 decreased with the severity of lung disease predominated in intensive care and was repeatedly used to justify it never being used there.

Subsequently a minimum of 150 patients probably died from major airway complications because the routine use of continuous waveform capnography in ITUs in the UK was not widely recommended until 2011 when NAP4 was published [2] and changed practice [3].

It would be very sad if this article’s findings were similarly interpreted by others to justify not routinely using lifesaving waveform capnography monitoring when ventilating neonates.

Airway deaths are particularly devastating [4] and I can only hope that for everyone's sake, the babies, their families and any staff 2nd victims history will not continue to repeat itself in neonatal intensive care [5].
David K Whitaker

David K Whitaker FRCA, FFPMRCA, FFICM, Hon FCARCSI
Consultant in Anaesthesia and Intensive care Manchester Royal Infirmary
References
1. Whitaker DK. Time for capnography - everywhere. Anaesthesia. 2011; 66: 544-9.
2. Cook TM, Woodall N, Harper J, Benger J. Major complications of airway management in the UK: results of the 4th National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 2 Intensive Care and Emergency Department. British Journal of Anaesthesia 2011; 106: 632-42
3. Cook TM. Airway complications – strategies for prevention. Anaesthesia 2018; 73: 93-111.
4. Baby’s family in call for action over ‘neglect’ finding in inquest https://www.yorkshirepost.co.uk/news/latest-news/baby-s-family-in-call-f... (accessed 07 July 2019)
5. Pathan N. British Broadcasting Corporation. Sick babies at risk from lack of breathing tube monitoring. https://www.bbc.co.uk/news/health-45197375 (accessed 07 July 2019)

Conflict of Interest
DKW is currently Chairman of the Patient Safety Committee of the European Board of Anaesthesiology. He has received lecture fees from Aguettant Ltd and Medtronic, all donated to Lifebox and travel expenses for the Global Capnography Project (GCAP) in Malawi from Medtronic.
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Conflict of Interest:
DKW is currently Chairman of the Patient Safety Committee of the European Board of Anaesthesiology. He has received lecture fees from Aguettant Ltd and Medtronic, all donated to Lifebox and travel expenses for the Global Capnography Project (GCAP) in Malawi from Medtronic.
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Published on: 12 November 2019
Prof Tim Cook
- TM Cook, Consultant in Anaesthesia and Intensive Care Medicine Mr
- Other Contributors:
  Katie Foy, Specialist Registrar in Anaesthesia
  
  Fiona E kelly, Consultant in Anaesthesia and Intensive Care Medicine
Dear Editor
We read with interest Dr Scrivens et al’s commentary [1]. The mother’s question - ‘should capnography be used for breathing tube monitoring?’ – captures the subject addressed in our ‘PICNIC survey’ [2]. Conversely, the authors examine a completely different question - ‘is capnography an optimum respiratory monitor in ventilated neonates?’
A respiratory monitor detects whether the end-tidal CO2 value usefully measures pulmonary ventilation or PaCO2. Although not our focus here, we are surprised the review omitted Kugelman’s study which reported waveform capnography monitoring in neonatal ICU (NICU) improved ventilation accuracy and neurological outcomes [3].
An airway monitor assesses ‘whether lung ventilation is taking place via a tracheal tube that is in the airway and is patent’. High rates of neonatal failed intubation, oesophageal intubation, accidental extubation and reports of associated patient harm all suggest the value of a reliable airway monitor in NICU. Waveform capnography rapidly detects correct intubation with few false positives and immediately detects displacement or disconnection, the evidence for which we have previously set out [4-6].
Some neonatologists argue that continuous waveform capnography cannot be used in neonates. It is used routinely in neonatal anaesthesia. Others use it routinely during transfer of small neonates (eg 400g) (personal communication Dr James Tooley, Consultant, Bristol) sometimes only for it...
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Dear Editor
We read with interest Dr Scrivens et al’s commentary [1]. The mother’s question - ‘should capnography be used for breathing tube monitoring?’ – captures the subject addressed in our ‘PICNIC survey’ [2]. Conversely, the authors examine a completely different question - ‘is capnography an optimum respiratory monitor in ventilated neonates?’
A respiratory monitor detects whether the end-tidal CO2 value usefully measures pulmonary ventilation or PaCO2. Although not our focus here, we are surprised the review omitted Kugelman’s study which reported waveform capnography monitoring in neonatal ICU (NICU) improved ventilation accuracy and neurological outcomes [3].
An airway monitor assesses ‘whether lung ventilation is taking place via a tracheal tube that is in the airway and is patent’. High rates of neonatal failed intubation, oesophageal intubation, accidental extubation and reports of associated patient harm all suggest the value of a reliable airway monitor in NICU. Waveform capnography rapidly detects correct intubation with few false positives and immediately detects displacement or disconnection, the evidence for which we have previously set out [4-6].
Some neonatologists argue that continuous waveform capnography cannot be used in neonates. It is used routinely in neonatal anaesthesia. Others use it routinely during transfer of small neonates (eg 400g) (personal communication Dr James Tooley, Consultant, Bristol) sometimes only for it to be removed on arrival at NICU! In veterinary practice it may be used in animals weighing 50g (personal communication, Dr Jonathan Cracknell, Wildlife Anaesthesia Services, Longleat, Wiltshire).
Proving the value of safety measures by randomised controlled trials (RCTs) is often impractical because of the rarity of the adverse outcomes the intervention is intended to prevent (here hypoxaemic brain injury or death). There are no RCTs that show outcome benefit of oximetry in anaesthesia or critical care, but its use is universal. Proving capnography improves outcomes via RCT may be challenging – though studying the impact on prompt recognition of incorrect intubation, disconnections and accidental extubation is feasible.
In 2011 waveform capnography was available in half of adult ICUs and these often used it infrequently [7]. There was significant resistance to the NAP4 recommendation for universal implementation, including senior intensivists stating its use was impossible and unnecessary - because ventilator parameters would readily identify problems. That some adult ICUs were using it widely and others not at all mirrors current NICU practice: this variation in practice merits urgent investigation and explanation. Four years after NAP4, 98% of adult ICUs had waveform capnography, using it routinely at intubation and for monitoring all ventilated patients [8]. Capnography in ICU is practical and it is now accepted in UK adult ICUs as a standard of care.
Neonates, in common with all humans, exhale carbon dioxide with every breath. Detection of this has the potential to be the most rapid and reliable monitor of airway integrity in neonates reliant on an artificial airway. In determining whether waveform capnography is the right tool in their setting it is important that the neonatal community start to ask the right question.
TM Cook
KE Foy
FE Kelly
References
1. Scrivens A, Zivanovic S, Roehr CC. Is waveform capnography reliable in neonates? Arch Dis Child July 2019 Vol 104 No 7 http://dx.doi.org/10.1136/archdischild-2018-316577
2. Foy K, Mew E, Cook T, et al United Kingdom paediatric and neonatal intensive care airway management: the PICNIC survey, Anaesthesia 2018; 73: 1337-44
3. Kugelman A, Golan A, Riskin A et al. Impact of Continuous Capnography in Ventilated Neonates: A Randomized, Multicenter Study. Journal of Pediatrics 2016; 168: 56-61
4. Cook TM, Foy K, Kelly F. Paediatric intensive care and neonatal intensive care airway management in the United Kingdom: the PIC-NIC survey. (Response to Mactier et al.) http://www.respond2articles.com/ANA/forums/thread/2670.aspx
5. Cook TM, Foy K, Kelly F. Paediatric intensive care and neonatal intensive care airway management in the United Kingdom: the PIC-NIC survey. (Response to Wyllie et al.) http://www.respond2articles.com/ANA/forums/thread/2677.aspx
6. Cook TM, Foy K, Kelly F. Paediatric intensive care and neonatal intensive care airway management in the United Kingdom: the PIC-NIC survey. Anaesthesia 2019; 74; 118-120
7. Cook TM, Woodall N, Harper J, Benger J. Major complications of airway management in the UK: results of the 4th National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 2 Intensive Care and Emergency Department. British Journal of Anaesthesia 2011; 106: 632-42
8. Cook TM, Woodall N, Frerk C. A national survey of the impact of NAP4 on airway management practice in United Kingdom hospitals: closing the safety gap in anaesthesia, intensive care and the emergency department. British Journal of Anaesthesia 2016; 117: 182-190
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Conflict of Interest:
None declared.
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