Basic principles of respiratory function monitoring in ventilated newborns: A review

Physiological and anatomical dead space in mechanically ventilated newborn infants

“…Our study has a number of strengths and some limitations. The CO 2 sensor had a low apparatus dead space and its mainstream position in the respiratory circuit allowed for a faster response time even at high respiratory rates . Another strength is that we studied a cohort that consisted of both term and extremely prematurely born infants.…”

“…The CO 2 sensor had a low apparatus dead space and its mainstream position in the respiratory circuit allowed for a faster response time even at high respiratory rates. 22 Another strength is that we studied a cohort that consisted of both term and extremely prematurely born infants. In addition, we routinely use shouldered endotracheal tubes that minimize leak, 23 high leak would introduce significant error to the measurements via shortening of the plateau phase of the expired CO 2 .…”

Determinants of pulmonary dead space in ventilated newborn infants

“…VD has been successfully used to predict survival in adults with acute respiratory distress syndrome [5], however, few studies have reported values of VD in ventilated infants: Schmalisch et al measured VD in 22 ventilated infants with a median gestation of 34.5 weeks and reported a median VD/kg of 2.3 ml/kg [2]. They used a combined flow/CO2 detector with a dead space of 2.6 ml which, given the small tidal volume of the premature infants, might have impacted on the results via rebreathing from the apparatus dead space [6]. In another study, the molar mass signal of an ultrasonic flow meter was used in 43 ventilated neonates with a mean gestational age of 28 weeks and a mean VD of 2.51 ml/kg was reported [7].…”

Is waveform capnography reliable in neonates?

“…According to a recent survey by Charles et al , use of exhaled CO 2 monitoring has increased in neonatal practice from 10% in 2008, 19% in 2012 to 84% in 2017 5 6. However, technologies involving waveform capnography seem at a stage of development not yet ready to be integrated into neonatal care 7 8. Currently, many neonatal units use a colorimeter attached to the ETT to detect exhaled CO 2 at the point of initial intubation, then TCCO 2 for ongoing monitoring.…”

“…Three review articles examined ETCO 2 monitoring: Molloy and Deakins12 concluded that ETCO 2 is as accurate as TCCO 2 but not as precise in estimating PaCO 2 and recommended the use of TCCO 2 . Schmalisch7 highlighted difficulties of using ETCO 2 in neonates; increased ventilator dead space, potential rebreathing of exhaled CO 2 , fast respiratory rates and low tidal volumes (which means that the expected plateau portion of the waveform, from which the ETCO 2 measurement is read, may not be long enough to give an accurate approximation of alveolar PCO 2 ) and potential for leaks from uncuffed ETTs. Van Vonderen et al 13 cited similar problems as reasons to use ETCO 2 only in conjunction with other forms of respiratory function monitoring.…”