title: Noninvasive capnometry for end-tidal carbon dioxide monitoring via nasal cannula in nonintubated neonates.
abstract: BACKGROUND
  Arterial blood gas analysis is the gold standard for assessing the adequacy of ventilation. However, arterial blood sampling may be associated with serious complications in neonates. The aim of the study was to utilize the side-stream capnometry measurement of end-tidal carbon dioxide (PetCO₂) via nasal cannula circuits and to verify the reliability of PetCO₂ in reflecting the arterial blood carbon dioxide(PaCO₂) level in nonintubated neonates.
  
  
  METHODS
  A retrospective medical record review analysis was performed in nonintubated neonates admitted to the neonatal ward in a medical center. Simultaneous arterial PaCO₂ and PetCO₂ levels were evaluated. PaCO₂ and PetCO₂ levels were compared by paired t test and were correlated using Pearson's correlation. The PetCO₂ bias was defined as the difference between PaCO₂ and PetCO₂, and was assessed by Bland-Altman plot analysis.
  
  
  RESULTS
  A total of 34 neonates were recruited, and data of 54 pairs of PaCO₂ and PetCO₂ levels were available for comparison. The average (mean ± SD) gestational age was 32.5 ± 4.2 weeks, and the average birth weight was 1881 ± 1077 g. There was a good correlation between PetCO₂ and PaCO₂ levels among all paired samples (r = 0.809, p < 0.001). When the data were divided into those with respiratory disease (n = 34) and those without (n = 20), significant correlation between PetCO₂ and PaCO₂ levels were both noted in the former group (r = 0.823, p < 0.001) and the latter group (r = 0.770, p < 0.001). The overall average mean value of PetCO₂ was lower than that of PaCO₂ (39.4 ± 8.8 mmHg vs. 41.3 ± 9.2 mmHg, p = 0.014). The difference between PetCO₂ and PaCO₂ levels was significant only among those with respiratory disease (38.8 ± 9.8 mmHg vs. 41.2 ± 10.3 mmHg, p = 0.027), but not among those without (40.5 ± 7.0 mmHg vs. 41.6 ± 7.2 mmHg, p = 0.289).
  
  
  CONCLUSIONS
  End-tidal CO₂ measurement by side-stream capnometry through nasal cannula could provide an accurate and noninvasive estimate of PaCO₂ levels in nonintubated neonates.
authors.affiliation: Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, No. 7 Chung-Shan South Road, Taipei, Taiwan.
authors.forename: Chih-Che
authors.initials: CC
authors.lastname: Tai
authors.forename: Frank Leigh
authors.initials: FL
authors.lastname: Lu
authors.forename: Pau-Chung
authors.initials: PC
authors.lastname: Chen
authors.forename: Suh-Fang
authors.initials: SF
authors.lastname: Jeng
authors.forename: Hung-Chieh
authors.initials: HC
authors.lastname: Chou
authors.forename: Chien-Yi
authors.initials: CY
authors.lastname: Chen
authors.forename: Po-Nien
authors.initials: PN
authors.lastname: Tsao
authors.forename: Wu-Shiun
authors.initials: WS
authors.lastname: Hsieh
mesh_terms: D001784:Blood Gas Analysis; D019296:Capnography / Q000295:instrumentation*; D057785:Catheters; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007235:Infant, Premature, Diseases / Q000175:diagnosis / Q000378:metabolism* / Q000628:therapy; D007442:Intubation, Intratracheal; D008297:Male; D015203:Reproducibility of Results; D012120:Respiration Disorders / Q000175:diagnosis / Q000378:metabolism* / Q000628:therapy; D012189:Retrospective Studies; D013990:Tidal Volume / Q000502:physiology