Objective.The performance of a point-of-care, noninvasive end tidalbreath carbon monoxide analyzer (CO-Stat End Tidal BreathAnalyzer, Natus Medical Inc.) that also reports end tidal carbon dioxide(ETCO₂) and respiratory rate (RR), was compared to established,marketed (predicate) devices in children (n = 39) and adults(n = 48) who are normal or at-risk of elevated CO excretion.Methods.Concentrations of end tidal breath CO (ETCO), room air CO,ETCO corrected for inhaled CO (ETCOc), ETCO₂, and RR were measuredwith the CO-Stat analyzer and the data compared to thoseobtained from the same subjects using the Vitalograph BreathCO monitor(Vitalograph, Inc.) for ETCOc and the Pryon CO₂ monitor (SC210 andSC300, Pryon Corp) for ETCO₂ and RR. Adults and children werestudied at three medical centers. The data were analyzed by paired t-tests andlinear regression. Bias and imprecision between the CO-Stat analyzer and thepredicate devices was calculated by the method of Bland and Altman.Results.Paired t-tests, performed on the three parametersmeasured with the CO-Stat analyzer and predicate devices showed that only theETCOc values in the adults and the ETCO₂ values in the childrenwere significantly different (lower, p 0.0001, and higher, p 0.0001, respectively). The mean bias and imprecision of the CO-Statanalyzer for adult ETCOc and children ETCO₂measurements were–0.9 ± 1.2 ppm and 0.4 ± 0.6%, respectively. Linearregression analysis for the ETCOc results in children and adults had a highdegree of correlation (r= 0.91 and 0.98, respectively).Conclusions.We conclude that in a clinical environment the NatusCO-Stat End Tidal Breath Analyzer performs at least as wellas predicate devices for the measurements of ETCOc, ETCO₂, and RR.