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.