This paper examines human-equipment interfaces (HMI) in hospital environments, focusing on the critical relationship between medical device design and patient safety. It defines HMI as the point of interaction between a machine and its operator, then illustrates how poor interface design in hospitals has led to serious medical errors involving infusion pumps, oxygen machines, and alarm systems. The paper discusses specific control measures—including design standardization, color coding, alarm redundancy, and ergonomic considerations—that manufacturers and facilities have implemented to reduce error risk. By analyzing real-world case studies of equipment-related injuries and deaths, the paper demonstrates why effective HMI design is essential to safe clinical practice.
Technological transformations have brought widespread use of machines and tools to the work setting. As a result, concepts such as human-machine and human-equipment interfaces have become increasingly prominent. In its simplest form, a human-machine interface (HMI) refers to the point or extent of interaction between a machine and its operator. Taken literally, it is the area of the machine and that of the human that interact during the execution of a task.
As the use of machines at the workplace increases, the HMI concept becomes more relevant. This is particularly important because machines and equipment continue to grow more complicated and advanced. As users make greater use of them, the risk of error increases. In response, manufacturers are under pressure to continually develop tools and machines that align with human anatomy, limitations, and skills to make the user-machine interface safer for users (Flasporer et al., 2002).
In a hospital setting, medical practitioners interact with a wide array of medical devices. For instance, practitioners must feed patients' health and medical records, as well as prescriptions, into a computer, in which case they interact directly with the screen through their eyes and with the keyboard or mouse through their hands. They must also infuse patients using infusion pumps, where they use both their eyes and hands to set the desired flow rate on the display surface. Additionally, practitioners use oxygen machines to treat patients and must set the flow control knob at desired levels. All these represent examples of user-machine interfaces in a hospital environment (Sawyer, 2014).
Though these interfaces are important to a patient's healing environment, they need to be carefully controlled in order to realize the desired outcomes. Manufacturers are required to design their equipment in line with humans' basic sensory and physical capabilities, which include reach, strength, manual dexterity, hearing, and vision (Sawyer, 2014). Effective equipment design is one of the key ways of controlling user interfaces and making them safer for both practitioners and patients.
Failure to control user interfaces in hospital settings could result in serious consequences. There have been numerous cases where user interfaces—both hardware and software—induced serious errors that resulted in injury and, at times, even death of patients (FDA, 2015).
A perfect example is when a nurse, not realizing that a newly acquired oxygen machine is scaled in discrete rather than continuous numbers, sets the control knob between 1 and 2 liters per minute, causing a patient to become hypoxic because there is no oxygen flow (Sawyer, 2014). Another common occurrence is when a nurse misreads 7 as 1 on the infusion pump, resulting in the over-infusion of a patient. In other cases, a nurse fails to enter dosage levels in a radiation treatment device simply because the device software did not prompt them for such data and instead picked up a default value without signaling this action (Sawyer, 2014). Additionally, crucial alarm systems are sometimes disabled without signaling to the user, merely because certain control buttons were pushed (Sawyer, 2014).
All these interface failures can have devastating effects. As such, they need to be controlled through effective equipment design. Designers ought to recognize that practitioners' performance could be influenced by fatigue, stress, electrical interference, dirt, heat, poor lighting, and noise. In order to minimize the risk of error, equipment needs to be designed in a manner that minimizes the amount of strength needed to make connections, allows for accurate distinctiveness and audibility of alarms, and ensures proper legibility of symbols (Sawyer, 2014). Understanding human factors in medical device design is therefore essential to patient safety.
In an attempt to improve the interface between users and hardware, devices have increasingly been designed with large consoles, properly spaced and easy-to-operate keys, unambiguous labels, and functional groupings of displays and controls. This approach ensures that users can easily differentiate between keys, knobs, and labels, and that the risk of inadvertent manipulation is kept considerably low (Sawyer, 2014). Shape and color coding that are in congruence with universal industry conventions are often used to make displays and controls easily identifiable and minimize the risk of misidentification and inadvertent activation.
Design controls have also been put in place to reduce the risk of patients dying as a result of improper installation of equipment. A documented case involved a patient who died from impeded air flow after a nurse installed an oxygen machine upside down (Sawyer, 2014). To prevent such errors, manufacturers now employ numbering of cables and hardware components for easy installation, color codes to help users make proper connections, and graphics to make user manuals easier to understand.
Alarms are another crucial component in hospital settings. However, if not properly designed, they could cause injury or even death. Alarm-associated problems include accidental disabling, inappropriate silencing, ambiguous meanings, delayed alarms, false alarms, and alarms that are not loud enough (Sawyer, 2014). To minimize the risk of such problems, facilities are increasingly ensuring that auditory and visual alerts are incorporated into their alarm systems.
Further, facilities are making greater use of critical alarm systems, which are more effective than conventional models owing to their ability to provide redundant visual and auditory signals (Sawyer, 2014). Modern alarms are also designed to indicate the source of the problem as well as mechanisms for querying this source, and visual indicators for showing the status of the problem. Color and code systems that correspond to universal conventions are increasingly being used to minimize the risk of accidents resulting from misguided actions (Sawyer, 2014).
As the state of technology progresses, the human-machine interface concept becomes more relevant. Positive outcomes can only be realized if humans interact safely with the equipment and machines that they use in executing their tasks. There have been numerous cases of injury or death resulting from wrongful installation of machines, inappropriate labeling of equipment, and other such errors. As a result, designers and organizations alike have put in place controls to make the human-equipment interface safer and less prone to error.
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