Assessment of sidestream end‐tidal capnography in ventilated infants on the neonatal unit

Abstract

ObjectivesContinuous monitoring of carbon dioxide (CO2) levels can be achieved by capnography. Our aims were to compare the performance of a sidestream capnograph with a low dead space and sampling rate to a mainstream device and evaluate whether its results correlated with arterial/capillary CO2 levels in infants with different respiratory disease severities.Working HypothesesEnd‐tidal carbon dioxide (EtCO2) results by sidestream and mainstream capnography would correlate, but the divergence of EtCO2 and CO2 results would occur in more severe lung disease.Study DesignProspective cohort study.Patient‐subject SelectionFifty infants with a median (interquartile range) gestational age of 31.1 (27.1‐37.4) weeks and birth weight of 1.37 (0.76‐2.95) kg.MethodologyConcurrent measurements of EtCO2 in ventilated infants were made using a new Microstream sidestream device and a mainstream capnograph (gold standard). Results from both devices were compared with arterial or capillary CO2 levels. The ratio of dead space to tidal volume (Vd/Vt) was calculated to assess respiratory disease severity.ResultsThe mean difference between the concurrent measurements of EtCO2 was −0.54 ± 0.67 kPa (95% agreement levels − 1.86 to 0.77 kPa), the correlation between the two was r = .85 (P < .001). Sidestream capnography results correlated better with partial pressure of CO2 (PCO2) levels in infants with less (Vd/Vt < 0.35; r2 = .66, P < .001) rather than more severe (Vd/Vt > 0.35; r2 = .33, P = .01) lung disease.ConclusionsThe sidestream capnography performed similarly to the mainstream capnography. The poorer correlation of EtCO2 to PCO2 levels in infants with severe respiratory disease should highlight to clinicians increased ventilation‐perfusion mismatch.

Non-invasive carbon dioxide monitoring in neonates: methods, benefits, and pitfalls

“…However, wide variation in EtCO 2 and poor correlation between EtCO 2 and PaCO 2 has been noted in critically ill preterm neonates. This is probably secondary to the V/Q mismatch in these newborns with more severe lung disease [ 31 ]. EtCO 2 measurements are expected to be lower than the PaCO 2 due to (i) intrapulmonary shunting with some of the arterial CO 2 bypassing the ventilated alveolar units, (ii) CO 2 being diluted in the conducting airways (anatomical dead space) that do not contribute to CO 2 production and (iii) portions of the lung that are ventilated but not perfused (alveolar dead space, that is increased in worsening lung disease).…”

Carbon dioxide monitoring in the newborn infant

“…Utilizing a microstream sidestream capnograph, the gradient of EtCO 2 to PCO 2 has been assessed in ventilated infants with and without pulmonary disease, with a higher gradient seen in the infants with lung disease (7.4 vs. 3.0 mmHg), 51 thereby suggesting this technology could be used as an early warning adjunct to provide clinicians with information regarding severity of pulmonary disease and alert them to changes in respiratory status 49 . Furthermore, this novel device has indeed been shown to better predict PCO 2 in ventilated infants with less severe lung disease than in those with more severe lung disease ( r 2 = .66 vs. r 2 = .38), likely due to higher physiological dead space and ventilation‐perfusion mismatching in the latter cohort 52 …”

“…Results from such a capnograph have been shown to accurately reflect alveolar CO 2 levels in healthy newborn infants 51 . Novel microstream sidestream end‐tidal capnography has further been validated against mainstream capnography in ventilated newborn infants and found to perform similarly (mean bias −4.1 mmHg, r = .9), suggesting the former is suitable for use in neonates 52 . In infants born prematurely, however, there is less correlation between sidestream and blood carbon dioxide values than those more mature infants ( r = .38 vs. r = .50), likely due to the larger relative anatomical dead space and dilution of exhaled CO 2 52 .…”

“…Novel microstream sidestream end‐tidal capnography has further been validated against mainstream capnography in ventilated newborn infants and found to perform similarly (mean bias −4.1 mmHg, r = .9), suggesting the former is suitable for use in neonates 52 . In infants born prematurely, however, there is less correlation between sidestream and blood carbon dioxide values than those more mature infants ( r = .38 vs. r = .50), likely due to the larger relative anatomical dead space and dilution of exhaled CO 2 52 . Furthermore, in those infants with less severe lung disease, as determined by a dead space to tidal volume ratio of less than 0.35, the sidestream end‐tidal CO 2 value better‐predicted blood CO 2 values than those with worse severity of lung disease (coefficient of determination [ r 2 ] = .70 vs. .33) thus suggesting the divergence of results could be utilized as an index of disease severity.…”

On Analyzing Capnogram as a Novel Method for Screening COVID-19: A Review on Assessment Methods for COVID-19

“…This allows for the monitoring of spontaneously breathing nonintubated subjects, as samples can be obtained via nasal cannulas. Furthermore, the administration of oxygen can continue unimpeded through the nasal cannula [70][71][72]. In this regard, the use of sidestream monitoring is increasing in popularity due to the improvements in patient comfort and acceptance associated with it.…”