title: Sidestream microstream end tidal carbon dioxide measurements and blood gas correlations in neonatal intensive care unit.
abstract: OBJECTIVE
  The study was designed to assess the use of newer sidestream microstream end tidal carbon dioxide (ETCO(2) ) device in predicting blood carbon dioxide (PCO(2) ) measurements in very low birth weight (VLBW = birth weight <1,500 g) and non-VLBW NICU neonates.
  
  
  METHODS
  Sidestream microstream ETCO(2) detectors were allowed time to calibrate and reach steady state prior to blood gas measurements. Blood CO(2) (PCO(2) ) and simultaneous ETCO(2) were recorded. Ratio of dead space to tidal volume (VD/VT) was calculated using modified Bohr's equation. Correlation coefficient, estimates of difference, standard deviation, and 95% limits of agreement between ETCO(2) and PCO(2) concentrations were calculated.
  
  
  RESULTS
  Two hundred eighty-six paired samples were collected from 48 ventilated NICU patients. Average PCO(2) and ETCO(2) were 58.4 and 50.6 with a correlation of 0.76. Subgroup analysis showed a correlation of 0.73 in 204 paired blood from 34 VLBW infants and 0.82 in 82 paired samples from non-VLBW infants. Estimates of difference ± standard deviation between PCO(2) and ETCO(2) concentrations in these three groups, respectively (ALL, VLBW, and non-VLBW) were 7.84 ± 9.96, 8.2 ± 10.16, and 6.95 ± 9.45. The correlation coefficient significantly improved in the VLBW group to 0.86 with dead space to tidal volume ratio (VD/VT) <30% (0.86 vs. 0.42; P < 0.001).
  
  
  CONCLUSIONS
  ETCO(2) measurements using sidestream microstream technology in VLBW demonstrated that the correlation of ETCO(2) and PCO(2) was moderate, but the agreement was less than adequate (bias > 5 mmHg in all groups). The results improved with lower VD/VT, suggesting that sidestream capnography is more reliable in conditions of less severe lung disease.
authors.affiliation: Division of Neonatology, Department of Pediatrics, Santa Clara Valley Medical Center, San Jose, CA, USA. bindya.singh@hhs.sccgov.org
authors.forename: Bindya S
authors.initials: BS
authors.lastname: Singh
authors.forename: Urquidez
authors.initials: U
authors.lastname: Gilbert
authors.forename: Sharad
authors.initials: S
authors.lastname: Singh
authors.forename: Balaji
authors.initials: B
authors.lastname: Govindaswami
mesh_terms: D015415:Biomarkers / Q000097:blood; D001784:Blood Gas Analysis; D019296:Capnography / Q000295:instrumentation*; D002245:Carbon Dioxide / Q000097:blood*; D006801:Humans; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight / Q000097:blood / Q000502:physiology*; D015931:Intensive Care, Neonatal; D016014:Linear Models; D012121:Respiration, Artificial; D013990:Tidal Volume
chemical_list: D015415:Biomarkers; D002245:Carbon Dioxide