An actual ISFET registration during spontaneous breathing is shown in figure 5. The
ISFET was calibrated using a blood sample, after an initial conditioning period of half
an hour, with the catheter tip in the iliac artery. The two dots are blood sample pH
values for comparison with the ISFET recording.
The registration shows that the ISFET measures with an accuracy within the values
that can be obtained with the usual intermittent sampling technique using an off-line
blood gas analyser.