Dose end-tidal carbon dioxide measurement correlate with arterial carbon dioxide in extremely low birth weight infants in the first week of life?

OBJECTIVE: To study the correlation and agreement between end-tidal carbon dioxide (EtCO2) and arterial carbon dioxide (PaCO(2)) in ventilated extremely low birth weight (ELBW) infants in the first week of life. METHODS: Retrospective chart review of all ELBW (<1,000 g) infants admitted to a level III NICU from January 2003 to December 2003. Data collected included demographic details and simultaneous EtCO(2) (mainstream capnography) and arterial blood gas values (pH, PaCO(2), PaO(2)). Outcome: The correlation coefficient, degree of bias with 95% confidence interval between the EtCO(2) and PaCO(2). RESULTS: There were 754 end-tidal and arterial CO(2) pairs from 31 ELBW infants (21 male and 10 female). The overall EtCO(2) values were significantly lower than PaCO(2) value. In only 89/754(11.8%) pairs, the EtCO(2) was higher than the PaCO(2). The overall bias was 5.6 +/- 6.9 mmHg (95% C.I. 5.11-6.09). The intraclass correlation coefficient was 0.81. Using EtCO2 ranges of 30 to 50 mmHg, the capnographic method was able to identify 84% of instances where PaCO(2) was between 35 (<35 = hypocarbia) and 55 mmHg (>55= hypercapnia). Conclusions: There is good correlation and agreement between end-tidal CO(2) and arterial CO(2) in ELBW infants in the EtCO(2) range 30-50 mmHg. End-tidal CO(2) monitoring can be helpful in trending or for screening abnormal PaCO(2) values in ELBW infants in first week of life.