APSF Grant Funds OR Vigilance Studies

Robert G. Loeb, M.D.

Editor’s Note: Dr. Loeb was a recipient of an APSF Research Grant in 1993 for his safety-related study, “Creating a Measure of Intraoperative Vigilance.” A brief summary report of his research follows.

Anesthesia vigilance is the continuous attention of the anesthesia provider to the patient’s physiologic status and other relevant factors that impact the patient’s well-being. Vigilance is important to patient safety, since failure of the anesthesia provider to detect or react to information is a prominent factor in preventable anesthesia mishaps. However, there have been few studies of anesthesia vigilance, in part because there were no accepted measurement techniques.

We previously investigated intraoperative attention to monitored data by measuring how quickly anesthesia residents detect an abnormal value of a simulated variable. However, a critique of this method is that the subject has no clinical impetus to watch the simulated variable. In this study, we tested a method where the subject watches for a signal in a real clinical variable and compares it to independent indicators of monitor surveillance and workload.

Ten anesthesia residents were studied while they administered anesthesia. During each case, they performed one of two vigilance tasks. In one (meaningless display), residents were instructed to monitor a clinically meaningless value and respond to the signal, “10.” In the other (systolic display), subjects monitored the systolic blood pressure and responded to the signal, “444.” Subjects pressed a button on the table of the anesthesia machine when they detected a signal. A new signal was presented at random intervals, every 5 to 15 minutes. An observer recorded every time the resident looked toward the monitor and for how long. Residents rated their own workload.

We found that response-time to detect a signal on the meaningless display correlated with residents’ monitor-watching activity, while response-time to detect a signal on the systolic display correlated with subjective workload. This suggests that tasks which use a clinically relevant signal may be better indicators of vigilance than those which use a clinically meaningless signal.

Surveillance of monitor displays is one element of vigilance. Technology is increasingly used in the provision of anesthesia care. But, the critical link as information passes from the data display to the anesthesia provider is poorly understood. This study was conducted to further develop a method to probe that human-machine interface in the real work environment. Similar methods could be used in the future to investigate the effect of human factors (such as fatigue or training), environmental factors (such as noise or workload), and equipment factors (such as display format) on the transmission of information from the machine to the human.

Dr. Loeb is from the Department of Anesthesiology, University of California, Davis, Medical Center, PSSB, Sacramento, CA.