Medical Monitoring Devices for the Home
Authors: Matt Schaning, B.B.E., Mark Mundschau, B.B.E., Anne Yatco, Elizabeth Omiatek, B.B.E., Peggy Keane
Coordinating Editor: Jack Winters, Ph.D.
Location: Medical Device Accessibility & Usability Laboratory
Current Version & Key Contributors: 1.1 (July 2006, Keane)
Past Versions & Key Contributors: 1.0 (August 2005, Yatco, Omiatek), 0.2 (August 2004, Schaning), 0.1 (July 2003, Mundschau)
Table of Contents
- Executive Summary
- Background
- Product Table
- Product Survey
- Product Evaluation
- Recommendations
- Acknowledgement
Executive Summary
This report examines features of medical monitoring devices, with a primary focus on devices that are portable and potentially used within the home. Users of such devices include patients, home caregivers, and practitioners. Some of these users may have disabilities. Factors taken into consideration include type of display, annunciation of patient alarms, and control schemes.
Medical monitors are divided into three major categories:
- bedside monitors (BSM),
- vital signs monitors (VSM) and
- central monitoring stations.
The latter can receive information over a hardwired or wireless network from multiple bedside and vital signs monitors, and are not covered in the scope of this report.
It was found that no company makes a product that is completely accessible to any potential user, although some companies have exemplary features (e.g., large visible alarm lights). Areas for potential future development include adding remote control capability to monitors, larger alarm lights, speech annunciation of critical alarms, controls with improved labeling, and wireless interfaces.
Background
The purpose of this report is to survey available medical monitors and to intuitively consider their accessibility to users with visual, auditory, and/or motor disabilities. This includes home users, both patient-consumers and caregivers. It also includes healthcare professionals, such as nurses and nursing aids. As a severe shortage of health professionals such as nurses looms on the horizon, hospitals look for new ways to retain clinical staff they already have and to bring new workers in - this can include professionals who may be older in age, and it can be expected that they will have suffered some hearing and vision loss. More accessible products would open up the doors within the healthcare profession with sensory and/or physical disability, who may help to allay the shortage in certain healthcare fields such as nursing. In addition, it would be useful to address the degree to which patients and caregivers could safely and effectively operate their own monitors within their homes.
Modern hospitals typically monitor a patient’s vital signs using a bedside monitor that can send data to a remote central monitoring station. The bedside monitor is likely portable and may be able to follow the patient anywhere in the hospital, eliminating the need to change connections whenever the patient is moved. As a variety of nurses, doctors, and clinicians are likely to come into contact with the patient, it is important that the monitoring devices are easily usable and accessible by all.
In considering accessibility, there are three main factors: the visual display of information; alarm announcement (audio, visual); and the form and layout of operator controls.
The first factor affecting video display is the type of display used. TFT-LCD monitors, such as those used in laptops, are the most common among bedside monitor displays. Older TFT displays typically have a narrow viewing angle of 45º each way, but more recent TFT monitor technology allows for a much wider viewing angle, approaching 85º. Another option is the Electro-Luminescent (EL) display, which uses a passive color matrix, as opposed to the active matrix of the TFT display. EL displays are not as bright as TFTs, but are known for higher picture quality, and respond to rapid changes in the display better. EL displays are typically monochrome, but some with color are beginning to appear. In addition to the higher picture quality, EL displays usually have viewing angles in excess of 160º.
Many vital signs monitors simply use 7-segment LEDs to display vital statistics (e.g. the CAS Medical Systems 740 Vital Signs Monitor). These are bright and viewable from a distance or at an angle. Some monitors may also use a backlit monochrome LCD screen to display information (e.g. the QRS Diagnostics Biolog 3000i). These generally cannot be viewed well from a distance as the text size is small and the resolution is low.
Also of interest in displays are the text sizes used. While data is typically displayed with large numerics, labels such as the name and units of the signal are often displayed with smaller font sizes. For healthcare professionals or home-based operators with vision limitations, information may be very difficult to read, and in a life-threatening situation while an alarm is going off, that can be a problem. However, often the most vitial information is provided in larger font.
Display of alarms is also of interest. While all monitors have an audio tone to signify an alarm condition, many only display the alarm by an LED on the front of the monitor or with on-screen messages. A few monitors have a large alarm light visible from any direction, which can be important in busy or noisy situations, particularly if the healthcare professional has some hearing loss. The audio output of the system is another feature to be considered, particularly in regards to the announcement of alarms.
Lastly, with regards to controls, the main concern is the amount of physical coordination required to work the controls based upon the control type and the layout. This does not take into account the physical control and coordination necessary to set up the sensors and modules on a patient. Secondarily, the availability of shortcuts, alternate control schemes (including multi-modal), and the ease of finding the correct control, due to labeling, etc. was considered.
Product Table
For an overiew and instructions on how to navigate within the product table click here.
Product Survey
The Product Table consists mostly bedside monitors, though there are a few vital signs monitors. Not every product has yet been included, with the items currently in the table having the most readily available information. In total, 37 of the 120 possible columns used by the RERC-AMI are included for this category.
Bedside monitors (BSM) share the capability to display multiple waveforms and parameters and can typically be connected to a local area network (LAN) so that information can be sent to other remote monitoring stations. Some monitors may also have a modem for long distance monitoring. Most of these monitors are portable, and some have the capability for wireless LAN connection and several hours of battery powered operation. Portability is important because it allows the unit to move with the patient.
Vital signs monitors (VSM) typically display only information such as non-invasive blood pressure (NIBP), pulse oximetry (SpO2), pulse (or heart rate) e and temperature. Some VSM collect ECG data, and may display an ECG waveform and possibly a SpO2 waveform. They may be network capable but often are not as most are used for one-time or short-term readings. Some telemetry units with display capabilities have been included into this category. The distinction between BSM and VSM is becoming less defined.
Newer vital signs monitors available on the market are more specialized in that they monitor only one or two parameters (eg. the Miasmo Radical, which only monitors pulse oximetery and pulse rate). This allows for a more affordable, more compact, and more portable product for the consumer.
Portability is a characteristic of vital signs monitors that is becoming increasingly more important. Portability allows the sophisticated technology of vital signs monitors to come into the home. Newer products are marketed with a focus on portability; newer products are often lightweight and self-contained. For example, the Welch Allyn Vital Signs Monitor 300 Series weighs approximately 5.4 lbs. and comes complete with its own temperature probe, pulse oximeter finger clip, and blood pressure cuff. This is appealing to consumers who, as caregivers, want a monitoring device that can go with them anywhere, or as homebound patients, want the convenience that portability provides.
For the columns describing the size of text, control text size may include text on screen for touch screens, or text printed onto the device’s shell or onto a button. We define small text as less than or equal to about 12 point font, medium text as approximately between 12 and 36 point font, and large is anything greater than 36 point text. The column entry targets the "typical" signal text size; there is often smaller text for labeling, and in some cases multiple sizes for signals.
The visual display of alarms is assigned a column, as this can be critical if the nurse cannot hear the alarm for whatever reason. The audio display is also considered, and at this point all monitors use a tonal annunciation. While the exact volume specs of the monitors are not available, almost all monitors have variable volume settings to accommodate their use in different areas of the hospital and an alarm silence button.
The reason for the speech and tonal columns is that it may be desirable to create a monitoring device that uses vocal annunciation of at least the most critical alarms. The main obstacle to doing this is the memory costs of fitting the sound files into the device, especially since many devices are designed to handle multiple languages, such that the same software contains all the languages, and it is set to the correct language upon installation on site. If speech were included, it would ideally be included for alternative languages on the monitor. While no monitors with speech have been found yet, there may be some in the future. Another helpful audio alarm cue is the tone. Having multiple tones allows for a person to distinguish the cause for the alarm without even looking at the monitor. For example, a high pitched alarm may indicate a life-threatening condition such as cessation of respiration or an irregular heart rate. A low pitched alarm may sound for a condition that is not as serious, such as body temperature increasing above a set limit. It would be ideal if a blind person could recognize the specific problem based on the sound of the alarm alone. This could be accomplished without fear of error using the speech annunciation.
The column on “number of waveforms” assesses how much information can be displayed at maximum and minimum on screen. The reason for this is that while the amount of information increases, the text size and waveform size decreases, which may make it more difficult for some to read the information.
The control type column lists the available controls for operating the machine. The choices are touch screen, buttons, keypad buttons, knob and wheel. A control knob can come in a variety of shapes, and usually pressing it in acts as a confirming for selecting action. Some knobs may be easier to grip than others based on their size. A control wheel, like the one found on the C3 from Phillips (see Figure to left), is reminiscent of a rotary phone dialing mechanism, without the auto-return of course. A keypad is a flat surface with inlaid buttons, much like a microwave oven has, whereas the control type of ‘buttons’ refers to raised buttons.
The “training required” column is subjective, and is based upon a 0 to 2 scale in which 0 means that anyone working with the device should be able to use the device effectively with little or no training and it has a very simple control system, with a limited number of buttons, etc. A device which scores a 1, as most do, may require some training to use, but is intuitive in its use. A user of similar devices, particularly a user of other products by the same company should be able to operate this machine effectively within a short period of time. The device may have some extra features that require more training. A device which scores a 2 requires extensive training and may be designed for use by a specialist, such as an advanced cardiac analysis monitor designed to be used by cardiologists. Currently there are no devices with a score of 2. These ratings have been assigned mostly by looking at the monitors, the control layouts and the companies’ own assessments.
Only three accessibility columns are provided, since it is difficult to provide such an assessment from review of web sites. The visual-blind and hearing-deaf scoring, on the scale 0-2, are based primarily on an assessment of available features. Notice that there is little variation between devices, as most products lack adequate multi-modal capabilities. For accessibility for difficulties with hand coordination, the amount of motor coordination required to operate each device was rated as a 2 to indicate fine control required, a 1 for some fine control required or a 0 for fine control not required. These assessments may be up to some debate as we are not able to actually work with each device and it is based mostly on the layout and clutter of controls, the size of buttons and the availability of alternate control schemes. Of note is that the MED-AUDIT project of the RERC-AMI includes a variety of such device features in its assessment methodology.
In inspecting devices from different companies, it can be seen that different theories of control layout were used in their design. For example, let’s compare the Dash 3000 from GE to the Spectrum from Datascope (Shown below). Both systems utilize a control knob for navigation of menus. Datascope says that every feature of the monitor is accessible using only the control knob. All of the buttons across the bottom of the machine are shortcuts to frequently accessed features. The Dash 3000 on the other hand has a touch screen for access to most menus, with some features accessed by button. The control knob can be used to access menus just as well as the touch screen. While the selection of shortcut buttons on the Datascope monitor does give immediate access to some features, it can also seem imposing to see that many buttons on a device such as this. Another item of note is the large alarm light built into the handle of the Dash 3000. This light is easily viewable from anywhere around the monitor, whereas the Spectrum only displays alarms onscreen.
Of note is that while the cost of monitors was found, it was generally from some type of discount distributor or other possibly unreliable source. The manufacturers should therefore also be contacted for the retail price, and we do not intend to update the column on as regular a basis.
Product Evaluation
While no formal evaluation has been performed, here are some preliminary comments.
In reviewing all of these systems, it becomes apparent that there currently is no product on the market that is completely accessible to all potential users. GE’s Dash series and Nihon Kohden’s Life Scope systems appear to have effective display of alarms, with large top mounted lights.
Most companies appear to be providing more and more portable products. However, Nonin’s Avant 400, which utilizes Bluetooth technology to allow the patient to be as far as 30 feet away from the display module during monitoring, and the Onyx 9550, a fingertip pulse oximeter that weighs less than 2 oz. are among the most portable products available today. For patients who require more comprehensive monitoring, the Welch Allyn Propaq LT provides the convenience of portability, weighing in at only 32 oz., while still offering complete vital signs monitoring.
WelchAllyn’s systems provide the most networking solutions, with the inclusion of nurse call functions and wireless LAN, but the displays may not be as effective for certain individuals with disabilities as some other systems. Siemens, with the Infinity 8000, gives the most versatility in display choices for a bedside monitor and includes Medical Interface Buses in its systems.
Most systems have similar control schemes, particularly in the use of a control knob. If there is one problem with the control knob it may be its shape. The knob used by every company has a small center piece which is gripped by the user. Users that have problems gripping small object may have a problem using the knob, and perhaps a wider knob would be a benefit. Also, Datascope’s design with the many shortcut buttons seems to be rather imposing when compared to the systems of other companies, although without actually using it, it is hard to assess it. The Phillips C3 appears to be very user-friendly because it a large control wheel and a few buttons, which are spaced apart well. If only the basic ECG data is needed, the hand-held Biolog 3000i from QRS Diagnostics would be useful for many persons.
No particular companies’ systems seem to stand out as a clear leader. The final choice will surely depend on the patient’s condition and what data is most important to assess that individual’s health.
Recommendations
While no product evaluation or detailed analysis has been done, here are several preliminary recommendations for future development in monitoring systems.
For mounted or portable devices, the redesign of existing controls, in particular widening the grip of control knobs, should be considered. Large alarm lights will most likely benefit any monitor, regardless of its primary function. It is also worth looking into adding speech to at least some monitoring systems, perhaps as an attachable module. This would allow, for instance, nurses or caregivers to identify alarms before they can see the display. It would be very helpful to put some of these devices through the R3 Accessibility Metric (MED-AUDIT) tool to help identify and refine other design improvements.
While most companies allow at least limited remote control from a central station, the addition of wearable and hand held remotes would be useful. Mobile versions of devices with, for instance, hand-held or wristwatch interfaces, would be welcome. There are clear tradeoffs in making devices mobile in that displays and controls are smaller, but for many applications and users, “access” would be improved if the device was wearable.
The development of universal remote control interfaces for these systems is needed. An interface standard, such as the new universal remote console (INCITS-V2) ANSI standard, would be a good path to start upon. The RERC-AMI has interests in this area, as reflected by the D3.2 V2 project that demonstrates an approach that would enable human-technology interfaces that adapt to the abilities and preferences of the user.
Acknowledgement
This work is supported by the Rehabilitation Engineering Research Center on Accessible Medical Instrumentation, funded by the National Institute on Disability and Rehabilitation Research, U.S. Department of Education Grant #H133E020729. All opinions are those of the authors.