The authors measured the partial pressure of carbon dioxide transcutaneously (PtcCO2) in 15 sick newborns and compared the PtcCO2to simultaneously measured partial pressure of arterial carbon dioxide (PaCO2). The PtcCO2values reflected changes in the PaCO2values. A linear regression on 106 paired PtcCO2and PaCO2values produced a correlation coefficient ofr= 0.91 with a slope of 1.89 and a y-intercept of –9.4. The authors found the measurement of PtcCO2to be a clinically useful method of continuously following the trend of PaCO2.