Current methodological and technical limitations of time and volumetric capnography in newborns

Abstract

Although capnography is a standard tool in mechanically ventilated adult and pediatric patients, it has physiological and technical limitations in neonates. Gas exchange differs between small and adult lungs due to the greater impact of small airways on gas exchange, the higher impact of the apparatus dead space on measurements due to lower tidal volume and the occurrence of air leaks in intubated patients. The high respiratory rate and low tidal volume in newborns, especially those with stiff lungs, require main-stream sensors with fast response times and minimal dead-space or low suction flow when using side-stream measurements. If these technical requirements are not fulfilled, the measured end-tidal CO2 (PetCO2), which should reflect the alveolar CO2 and the calculated airway dead spaces, can be misleading. The aim of this survey is to highlight the current limitations of capnography in very young patients to avoid pitfalls associated with the interpretation of capnographic parameters, and to describe further developments.

Effect of Transcutaneous Electrode Temperature on Accuracy and Precision of Carbon Dioxide and Oxygen Measurements in the Preterm Infants

“…In addition, end-tidal monitoring can underestimate CO 2 levels. [17][18][19] Monitoring end-tidal CO 2 at the distal end of a double-lumen endotracheal tube may be useful, but these tubes are not always used for neonates. 20 Given these issues, transcutaneous monitoring is the best option at this time for continuous CO 2 monitoring.…”

Determinants of pulmonary dead space in ventilated newborn infants

“…The strengths of our study include the use of the Capnostat-5 which is a low-dead space, mainstream CO2 detector which introduced less than one millilitre of apparatus dead space. We measured pulmonary dead space in a cohort of 61 subjects that included extremely prematurely born infants and used the Bohr/Enghoff equation, which is the most reliable method to calculate dead space in extremely low birth weight infants [16]. We also measured TPTEF/TE in ventilated infants during spontaneous breathing thus avoiding the error relating to mechanical ventilation in our assessment of expiratory airway function.…”

Ventilation Efficiency and Respiratory Muscle Function at Different Levels of CPAP in Intubated Prematurely Born Infants

“…Previous studies question the validity of tidal capnographic measurements in premature infants due to technical limitations that arise from the high proportion of instrumental dead space to V T and the breathing pattern of premature infants, which involves high rates and, commonly, the absence of an alveolar plateau phase. 31 In our study, however, we used a capnograph with the lowest available dead space, so this error has been minimized. Also, because the same methodology was used to measure P ETCO 2 , the relative change in P ETCO 2 at different levels of CPAP would also be valid.…”