Transcutaneous measurement of carbon dioxide tension: effect of sleep state in term infants.

Transcutaneous measurement of carbon dioxide tension (tcPO2) was used to assess the effect of sleep state on arterial carbon dioxide tension (PaCO2) in infants. Initially, tcPCO2 was correlated with PaCO2 in 50 sick preterm and term neonates with indwelling arterial lines. At a skin electrode temperature of 42 degrees C, the correlation coefficient between tcPCO2 and PaCO2 was .95. In eight healthy term infants there was a small but significant decrease in tcPCO2 of 2 +/- 1 mm Hg (P less than .001) during active as compared to quiet sleep. This decrease in tcPCO2 was accompanied by a significant decrease in transcutaneous oxygen tension (tcPO2) of 5 +/- 4 mm Hg (P less than .02) as has been previously described. The simultaneous decrease of both tcPCO2 and tcPO2 appears to indicate ventilation/perfusion inequalities in these infants during active sleep. These findings illustrate that tcPCO2 can accurately predict PaCO2 in infants and that this is a useful technique for studying neonatal respiratory control during various stages of sleep.