Assessment of sidestream end‐tidal capnography in ventilated infants on the neonatal unit
Emma Williams, Theodore Dassios, Anne Greenough
Abstract
Abstract Objectives Continuous monitoring of carbon dioxide (CO 2 ) 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 CO 2 levels in infants with different respiratory disease severities. Working Hypotheses End‐tidal carbon dioxide (EtCO 2 ) results by sidestream and mainstream capnography would correlate, but the divergence of EtCO 2 and CO 2 results would occur in more severe lung disease. Study Design Prospective cohort study. Patient‐subject Selection Fifty 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. Methodology Concurrent measurements of EtCO 2 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 CO 2 levels. The ratio of dead space to tidal volume (Vd/Vt) was calculated to assess respiratory disease severity. Results The mean difference between the concurrent measurements of EtCO 2 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 CO 2 (PCO 2 ) levels in infants with less (Vd/Vt < 0.35; r 2 = .66, P < .001) rather than more severe (Vd/Vt > 0.35; r 2 = .33, P = .01) lung disease. Conclusions The sidestream capnography performed similarly to the mainstream capnography. The poorer correlation of EtCO 2 to PCO 2 levels in infants with severe respiratory disease should highlight to clinicians increased ventilation‐perfusion mismatch.