Transcutaneous carbon dioxide and oxygen tension in newborn infants: Reliability of a combined monitor of oxygen tension and carbon dioxide tension

We evaluated a new combined sensor for monitoring transcutaneous carbon dioxide tension (PtcCO₂) and oxygen tension (PtcO₂) in 20 critically ill newborn infants. Arterial oxygen tension (PaO₂) ranged from 16 to 126 torr and arterial carbon dioxide tension (PaCO₂) from 14 to 72 torr. Linear correlation analysis (100 paired values) of PtcO₂ versus PaO₂ showed anr value of 0.75 with a regression equation of PtcO₂=8.59+0.905 (PaO₂), while PtcCO₂ versus PaCO₂ revealed a correlation coefficient ofr=0.89 with an equation of PtcCO₂=2.53+1.06 (PaCO₂). The bias between PaO₂ and PtcO₂ was –2.8 with a precision of ±16.0 torr (range, –87 to +48 torr). The bias between PaCO₂ and PtcCO₂ was –5.1 with a precision of ±7.3 torr (range, –34 to +8 torr). The transcutaneous sensor detected 83% of hypoxia (PaO₂ <45 torr), 75% of hyperoxia (PaO₂ >90 torr), 45% of hypocapnia (PaCO₂ <35 torr), and 96% of hypercapnia (PaCO₂ >45 torr). We conclude that the reliability of the combined transcutaneousPo₂ andPCo₂ monitor in sick neonates is good for detecting hypercapnia, fair for hypoxia and hyperoxia, but poor for hypocapnia. It is an improvement in that it spares available skin surface and requires less handling, but it appears to be slightly less accurate than the single electrodes.