The Complexities of the Human-Medical Device Interface

Human factors, as a highly interdisciplinary and systems science, has already established the tremendously important role associated with the human-machine interface in ensuring safe, usable, and human-friendly products. For users of medical devices, however, this interface is significantly more complex because the patient is often, quite literally, an extension of the device. Through their direct electrical (e.g., electrocardiogram), fluidic (e.g., arterial blood pressure line), and/or pneumatic (e.g., ventilator) connections to various medical devices, patients become one with the technology. Not only are the machines capable of altering patient physiology, but the patient is also capable of altering the machine, e.g., through the triggering of alarms. Such an alliance between patient and machine is not only dynamic, it may also be highly fragile and unstable depending on the changing pathology of the patient. This complexity places a significantly increased cognitive burden on the clinical users of medical devices. Correspondingly, designers of medical devices need to be acutely aware of this burden when designing and testing the effectiveness and quality of their product interface. Hospital-based biomedical equipment technicians (BMETs) and clinical engineers will also do well to stay mindful of these complexities during device troubleshooting and, especially, when introducing new technology into the hospital environment. The focus of this paper is on the subtle, almost subliminal nature associated with many aspects of the human-medical device interface, some of which include the simple use or misuse of color, obscure panel labeling, or switch behavior. Collectively, however, they all may affect how the machine and clinician user will eventually “get along” with each other—and how effectively and safely the device will be used. The profoundly-instrumented, acutely-ill patient represented in Figure 1 continues to be more the norm rather than the exception in many hospital critical care units. Such patients may have multiple indwelling catheters, be connected to multiple infusion pumps, have direct electrical connections to physiological monitors and/or electrosurgical ground electrodes, and be intubated and connected to a ventilator as well. Obtaining or delivering clinically useful, real-time information or therapeutics is, in fact, precisely why these patients are instrumented in the first place. These obvious physical connections to and from the patient, however, do not represent the only interface. As further illustrated in Figure 2, there are additional “connections” between the clinician and the device and between the clinician and patient. These create, in effect, a closed-loop system. The overall safety and effectiveness of this patient-device-clinician system may also be profoundly affected by the environment in which they all reside. It is in this total systems context that the full impact, importance, and complexities of these multiple interfaces become apparent. Most of the medical errors related to such systems ocLarry Fennigkoh, PhD, PE, CCE is a professor within the biomedical engineering program at the Milwaukee School of Engineering. Email: fennigko@msoe.edu Figure 1. Through their direct connection to many medical devices, critical care patients become extensions of these devices.