Cable-testing device fails to indicate that hypertension is artifactual.

A patient undergoing neurosurgical anesthesia was noted to have a mean systolic/intraarterial pressure of 190/135 mm Hg, whereas the mean systolic/noninvasive blood pressure was 110/77 mm Hg. The problem was traced to a short circuit between the contacts in two adjacent sockets at the transducer-end of the interface cable. The short circuit prevented sufficient attenuation of the excitation voltage from the bedside monitor to the pressure-sensitive bridge circuit of the transducer. A test device (Cable Checker, Viggo-Spectramed, Oxnard, CA) containing a resistance network that could be attached to the interface cable in place of the transducer incorrectly indicated that the cable was functioning properly. The malfunction was confirmed by exposing the transducer to known static pressures. The manufacturer modified the transducer end of its interface cable to reduce the likelihood of a similar problem recurring. Subtleties of the function of the disposable transducer, reasons for a disparity between systolic intraarterial pressures and noninvasive blood pressures, and methods for bedside testing of intraarterial pressure equipment are discussed.