Mainstream end-tidal carbon dioxide monitoring in the neonatal intensive care unit.
BACKGROUND
Continuous noninvasive monitoring of arterial carbon dioxide (CO2) in neonatal intensive care unit (NICU) patients would help clinicians avoid complications of hypocarbia and hypercarbia. End-tidal CO2 monitoring has not been used in this population to date, but recent technical advances and the introduction of surfactant therapy, which improves ventilation-perfusion matching, might improve the clinical utility of end-tidal monitoring.


OBJECTIVE
To determine the accuracy and precision of end-tidal CO2 monitoring in NICU patients.


METHODS
Nonrandomized recording of simultaneous end-tidal and arterial CO2 pairs.


METHODS
Two university NICUs.


METHODS
Forty-five newborn infants receiving mechanical ventilation who had indwelling arterial access, and a predefined subsample of infants who were <1000 g birth weight, <8 days of age, and who received surfactant therapy (extremely low birth weight -ELBW- <8).


METHODS
The correlation coefficient, degree of bias, and 95% confidence interval were determined for both the overall population and the ELBW <8 subgroup. Those factors which significantly influenced the bias were identified. The ability of the end-tidal monitor to alert the clinician to instances of hypocarbia or hypercarbia was determined.


RESULTS
There were 411 end-tidal/arterial pairs analyzed from 45 patients. The correlation coefficient was 0.833 and the bias was -6. 9 mm Hg (95% confidence interval, +/-11.5 mm Hg). The results did not differ markedly in the ELBW <8 infants. Measures of the degree of lung disease, the ventilation index and the oxygenation index, had small influences on the degree of bias. This type of capnometry identified 91% of the instances when the arterial CO2 pressure was between 34 and 54 mm Hg using an end-tidal range of 29 to 45 mm Hg. End-tidal values outside this range had a 63% accuracy in predicting hypocarbia or hypercarbia.


CONCLUSIONS
End-tidal CO2 monitoring in NICU patients is as accurate as capillary or transcutaneous monitoring but less precise than the latter. It may be useful for trending or for screening patients for abnormal arterial CO2 values.
Rozycki
H J
HJ
Department of Pediatrics, Virginia Commonwealth University, Richmond, Virginia, USA.
Sysyn
G D
GD
Marshall
M K
MK
Malloy
R
R
Wiswell
T E
TE
D019296:Capnography; D002245:Carbon Dioxide / Q000032:analysis* / Q000097:blood*; D006801:Humans; D007231:Infant, Newborn / Q000097:blood*; D019102:Infant, Very Low Birth Weight / Q000097:blood; D007363:Intensive Care Units, Neonatal; D016015:Logistic Models; D008991:Monitoring, Physiologic / Q000379:methods*; D011663:Pulmonary Surfactants / Q000627:therapeutic use; D012121:Respiration, Artificial
D011663:Pulmonary Surfactants; D002245:Carbon Dioxide