Considering a real-time location system (RTLS)? Technology matters. As recently reported in the DOTMed article “Ultrasound Versus IR: Making decisions about real-time location systems,” one size of RTLS technology does not fit all. Here’s a more in-depth primer of infrared technology vs. ultrasound – two prominent technologies utilized in the healthcare RTLS and indoor positioning space today.
While there are multiple applications for radio frequency (RF) and Bluetooth Low Energy (BLE) in a traditional RTLS application like asset management - and frequently an infrared-based system or an ultrasound-based system will augment coverage by using complementary technologies - the purpose here is to demonstrate the indisputable facts, rooted in physics, about light (infrared) vs. sound (ultrasound) in the healthcare environment. Here are the points to consider.
- Since IR is dependent on light, it can be affected by materials that interact with light. For example, IR passes through glass, therefore, light-masking materials, like blinds, need to be applied to glass partitions, windows, doors, etc. which can be onerous in modern hospital design.
- Fluorescent light can affect the accuracy of IR.
- Light reflection from floors and in-room monitors can be problematic.
- Many transmission and blocking devices are required to achieve bay-level accuracy due to the need to control the light signals.
- Lithium batteries in the infrastructure, while long-lasting, are significantly more expensive than alkaline and require expensive disposal procedures due to their environmental impact. Lithium batteries can also be a safety hazard due to the volatile and flammable chemical compounds that are pressurized inside battery cells.
- Location resolution of IR can be measured to within a few feet.
- Installation, testing, certification and maintenance of an IR-based RTLS can be labor-intensive due to the number of transmission devices required. Consider the example below:
- An ambulatory recovery room with four bays separated by curtains would require as many as fourteen location devices to deliver bay-level accuracy due to the need to create “zones,” to control the light and ensure line-of-sight which directly affects accuracy (see figure 1).
- Once installed, transmitters need to be constantly monitored and tuned or adjusted in order to optimize performance and deliver the specified accuracy primarily due to the challenges of containing and managing the properties of light. This can require a significant amount of resources to manage. One IR-based system installed at large, multi-facility healthcare system in North Carolina (500+ beds) requires more than ten full-time personnel to manage optimization of the RTLS system as well as routine tag and transmitter maintenance (tag assignments and battery replacements).
- Sound can be easily contained – even in glass enclosures. Think of sound-proof recording studios mostly constructed of glass. Light passes through. Sound does not.
- No physical masking or blocking of ultrasound signals are required to make the system work.
- Fewer devices are required to deliver bay level accuracy. Each ultrasound transmission device can create up to four distinct zones vs. only one zone per IR-based location transmitter.
- Standard 1.5V D-cell alkaline batteries are more economical and easier to recycle reducing the environmental impact. The lower power consumption due to the physics of ultrasound allow for extended battery life.
- Sound has near perfect reflection so there are no propagation issues in buildings.
- Resolution of ultrasound can be measured to within a few inches.
- Installation, testing, certification and maintenance of an ultrasound-based RTLS can be described as “set it and forget it.” Monitoring for accuracy is minimal and the need to make adjustments is rare. Consider the example below:
- An ambulatory recovery room with four bays separated by curtains would require three location transmitters. Each transmitter can facilitate the creation of four distinct bays (see figure 2).
- Once installed, tested and certified, transmitters are set and require little-to-no monitoring or adjustments. No re-tuning or optimization is needed. One ultrasound-based RTLS installed in a large, mid-western, multi-facility healthcare system (500+ beds) requires less than two full time employees to manage. The majority of the employees’ time is spent on routine tag and transmitter maintenance (assigning tags/badges and replacing batteries).
RTLS programs require thoughtful investment to implement. The value of having RTLS, however, cannot be overstated in terms of meaningful improvements in quality, patient satisfaction, compliance, workflow, infection control and more. The amount of time it takes to recoup an investment in technology is always top-of-mind. When considering an RTLS, technology platform decisions matter - especially with regard to accuracy, infrastructure, and ongoing maintenance which all contribute to cost-of-ownership and speed of return on investment.