Capnography has been used by the ambulance service for quite some time now—but it's not always part of assessing the non-cardiac arrest patient. Waveform capnography is embedded into the Resuscitation Council UK (RCUK) (2015) Advanced Life Support (ALS) resuscitation guidelines, but has not been included in many other areas of practice as is advocated by some healthcare providers. For example, author, firefighter and paramedic, Troy Valente mentions this early on in his book Capnography—King of the ABCs: A Systematic Approach for Paramedics. Despite him having written this in 2010, this topic remains an area that paramedics could learn a lot more about. It is only 69 pages long but Valente has managed to include a substantial amount of information, all tailored to paramedics.
‘The Basics’
Chapter 1 entitled ‘The Basics’ provides an overview of the technology behind capnometry/capnography, the various available options of measuring EtCO2 levels and a detailed look at all phases of the respiratory cycle, and how they are presented in a waveform. Furthermore, Valente discusses causes of artefact that may alter the patient's waveform and how to deal with them.
‘A Systematic Approach’
Chapter 2, ‘A Systematic Approach’, and Chapter 3, both evolved from Valente's personal learning diary and notes he made to facilitate his own learning, eventually leading to this book. According to his own experiences, capnography in non-cardiac arrest patients has not been sufficiently addressed by the current literature—an area he feels that the ambulance service, in the USA, uses it for the most.
Before discussing integration of capnography into patient assessment, Valente highlights that paramedics or others unfamiliar or inexperienced with capnography should be using it as much as possible. This allows exposure and experience with the technology, before having to use it when dealing with a critically ill patient. This builds confidence with the equipment and its diagnostic value in practice. Ventilation-Perfusion mismatch (V/Q mismatch), the role of carbon dioxide in the body, hypo- and hypercapnia, as well as hypo- and hyperventilation, are all discussed in this chapter.
‘Non-Intubated Applications’
Chapter 3 follows on from chapter 2, and focuses on the value of capnography in non-intubated patients. Valente starts this section with a case study, before moving on to specific respiratory emergencies (respiratory tract infections, asthma vs. chronic obstructive pulmonary disease (COPD), congestive cardiac failure (CCF)/congestive heart failure (CHF) vs. COPD, pulmonary embolism (PE), anxiety and seizures) and how CO2 levels are affected. This highlights the benefits of obtaining EtCO2 readings in non-intubated patients and makes a strong case for EtCO2 monitoring and its diagnostic value, while not omitting potential challenges and pitfalls. Non-invasive positive pressure ventilation (NIPPV) is also discussed, before touching on other areas that may benefit from capnography, such as use during naloxone hydrochloride administration to more easily achieve the desired effect, particularly if attempting to leave the patient in a ‘groggy’ state.
‘Intubated Applications’
Chapter 4 covers intubated applications, which have not only been a point of discussion in paramedic practice in the UK, but also in the USA. Capnography, while already being used in endotracheal intubation and with supraglottic airways to confirm placement, does not come without potential pitfalls that the user needs to be aware of. Valente highlights the benefits of waveform capnography over colorimetric options and capnometry (numerical output only), and further highlights its superiority over auscultation as the best means of confirming tube placement.
While currently not part of paramedic practice in the UK, the administration of sodium bicarbonate during cardiac arrest and its potential impact on EtCO2 readings is also discussed. This carries no significance within current UK paramedic practice guidelines, but is still worth knowing about, as it may be something that could be encountered when working in interprofessional teams. Return of spontaneous circulation (ROSC) and rising intracranial pressure, as well as the role of capnography, are also discussed, before the book concludes with a set of notes.
‘Capnography Cliff Notes’
An executive summary entitled ‘Capnography Cliff Notes’ across six A5-sized pages summarises all key facts from the book, divided by chapter. This is an ideal quick reference section which, on its own, makes purchasing the book totally worthwhile.
References are included at the end of each chapter, allowing the reader to link Valente's statements and information to research, thereby also allowing for full transparency.
Conclusion
One thing worth pointing out is that on page 3, where Valente describes the functionality of pulse oximetry in relation to capnography, stating that pulse oximetry relies on measuring ‘the color of the hemoglobin’ to calculate SpO2 levels, this does not appear to be correct, as absorption of light of certain wavelengths and the amount of light absorbed are generally used to calculate SpO2 levels. Other than this small error, his insight into the use of capnography and pulse oximetry by paramedics is definitely clear and has been well researched.
There is no other book that provides a more condensed, but still comprehensive, insight into capnography for paramedics. This should be a recommended piece of reading for everyone who has capnography available or is considering whether to invest in this technology.