[Significance of tcPO2 limit values in classification of cardiotocograms]

The continuous transcutaneous measurement of oxygen pressure has got an important method for the improvement of CTG-changes. A quantitative evaluation of the tcPO2-curve allows a better prediction of hypoxemia and acidosis with help of the CTG. Precondition is the examination of bound-values from the tcPO2-parameters: Baseline of oxygen pressure (PB), decrease of oxygen pressure (PD) and its delay time (DL). For this purpose we used 1 027 contraction patterns from 48 tcPO2-CTGs with 12 000 single parameter-values. It seems, that 11-12 mmHg (1,47-1,6 kPa) is a significant bound. CTG-pattern with PB greater than or equal to 15 mmHg (2 kPa) are not connected with hypoxemia and PB-values less than or equal to 10 mmHg (1,33 kPa) show the hypoxemic image of the CTG. The contraction-related decrease of oxygen pressure (PD) and its delay time (DL) are useful for estimation of the importance of variable decelerations. PD less than 2 or 3 mmHg (0,27-0,4 kPa) and DL higher than 46 seconds allow a classification of variable decelerations to the not hypoxemic type. PD equal to or greater than 5 mmHg (0,67 kPa) and DL between 40 and 20 seconds are suspicious for the hypoxemic type. These investigations are the supposition for a computer-aided classification of CTG-pattern with bound-values of the tcPO2-curve.