[Online recording of monitor data. The artifact problem]

Increasing numbers of monitors at the anaesthesiologist's workplace, providing more than 20 different parameters of the patient's condition, have already made it impossible to record all the values in a handwritten form. Consequently, this most common method of record-keeping must be incomplete and inaccurate. In recent years computerised data-acquisition systems have been introduced into clinical practice in order to produce more reliable records. But after a 7-year experience in the use of such a system in cardiac anaesthesia, we have recognised certain problems that remain to be solved before automated record-keeping will achieve wider acceptance. The first is the handling problem, which was discussed in a previous paper. The second major problem is the appearance of artifacts, caused mainly by mechanical manipulations during the operation. In this paper, 300 courses of anaesthesia that were recorded online during different cardiac surgery procedures were examined and the incidence as well as the kind of artifacts occurring were evaluated. Algorithms were developed for each haemodynamic parameter to suppress these artifacts automatically by a subsequent analysing process; the efficiency of that "artifact filter" was validated in 35 of the 300 cases. Based on more than 30,000 values for each parameter, the incidence of artifacts was 3%-7%. However, only 0.1%-0.5% of the artifacts could not be eliminated by the filter. The method described here provided acceptable graphic printouts of the most important haemodynamic parameters (Figs. 1b and 2b) and would also be suitable to serve as an input filter for automatically running anaesthesia data-examination processes, which are currently being developed in our clinic.