An evaluation of the N-CAT, a new arterial tonometer.

The N-CAT is a newly developed arterial tonometer (TBP) monitor able to determine systolic, diastolic and mean blood pressures continuously and noninvasively. The aim of this study was to evaluate the accuracy and reliability of the TBP compared with directly measured invasive blood pressure (IBP) in 14 patients before and after elective coronary artery bypass surgery. Although the TBP was able to track changes in systemic pressure, before and after CPB, bias and precision for TBP monitoring did not meet the standard criteria for equivalency for noninvasive blood pressure to invasive blood pressure. We were unable to monitor TBP in two patients. Approximately 40% of all before and after CPB mean TBP pressure values differed from mean IBP by more than 10 mmHg. Moreover, there were discrepancies of sufficient magnitude and duration that limits the clinical usefulness of the N-CAT. Potential users should not rely exclusively on TBP values when making clinical decisions. Technological improvement is needed before its clinical use is recommended.