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Is waveform capnography reliable in neonates?
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  • Published on:
    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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    Conflict of Interest:
    None declared.
  • Published on:
    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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    Conflict of Interest:
    None declared.
  • Published on:
    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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    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.