Sensors and Insensibility: Monitoring Anaesthetic Activity with RFID Bryan Houliston, Dave Parry AURA Laboratory, School of Computing & Mathematical Sciences, Auckland University of Technology Level 1, 2-14 Wakefield Street, Auckland 1010, New Zealand
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Alan Merry Department of Anaesthesiology, University of Auckland Private Bag 92019, Auckland 1010, New Zealand
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Abstract This paper documents work-in-progress to use Radio Frequency Identification (RFID) technology as part of the clinical assessment of a system to improve patient safety during anaesthesia. RFID equipment has been selected and set up to record anaesthetists’ movements. The next stage will analyse the collected data to accurately identify anaesthetic activity.
1. Introduction The Integrated Drug Administration and Automated Anaesthesia Record System (IDAS: Safer Sleep LLC, Nashville, Tennessee) [1] is a collection of tools and processes designed to improve patient safety during anaesthesia. IDAS is currently undergoing a multi-modal clinical assessment, comparing the system with anaesthetists’ existing, generally ad-hoc, processes. The primary data collection method is direct observation and classification of anaesthetist activity. To triangulate with the observation, we are using RFID technology to monitor some activities that are of particular interest: preparing drugs, performing injections, updating the manual anaesthetic record, and sitting down. This paper documents the work done so far. Section 2 provides a brief introduction to RFID technology, and previous attempts to use it for activity detection. Section 3 describes the RFID equipment chosen for the current project. Section 4 outlines how the RFID data will be analysed, alongside other data sources. Finally, section 5 provides a conclusion.
2. RFID and Activity Detection At their most basic level, RFID tags and readers provide very similar functionality to barcode labels and scanners. But RFID offers a number of advantages, most notably the ability to read multiple tags simultaneously without requiring a line-of-sight between tag and reader [2]. Recent research exploring the use of RFID for activity monitoring suggests two broad approaches. The first is locationbased, with readers placed at key locations, and tags on people and objects of interest. This approach has been applied to workers in an office [3], and patients going through pre-op and post-op procedures [4]. The second approach is userbased, with a person wearing or carrying a reader, and tags on objects and locations of interest. This approach has been used to support assisted living [5], and the assessment of trainee anaesthetists [6].
3. Gathering Data with RFID Given the positive results reported in [6], we first considered a user-based approach, with anaesthetists wearing a matchbox-sized reader. However, we found it unsuitable for use in actual anaesthetic procedures for two major reasons. Firstly, the reader’s battery required recharging after less than two hours. And secondly, its very short read range necessitated tagging many syringes and injection ports, greatly increasing the required preparation time. Instead we have opted for a location-based approach. Four to six RFID readers are placed around the theatre, as indicated in table 1. Where possible they are concealed to minimise distractions to the anaesthetist. We selected Tracient Ultra-High Frequency (UHF) readers. They are the size of a typical TV remote control, can reliably read tags up to a range of around 30 cm, and run for seven hours on a full battery charge.
Each anaesthetist wears five RFID tags. One is on the back of their scrubs, to be sensed when they sit down. The other four are embedded in a wristband worn on their dominant hand. The tags are spaced around the wristband such that one is on the top of the wrist, one on the bottom, one on the inside, and one on the outside. Table 1 - RFID Equipment Setup To Monitor...
A reader will be placed...
Reading every...
Drug preparation
On the drug trolley work surface
3 seconds
Update of manual anaesthetic record
Inside a hollow clipboard
3 seconds
Injections to wrist (if required)
On the arm support of the operating table
2 seconds
Injections to neck (if required)
At the head of the operating table
2 seconds
Injections into IV line (if required)
Suspended from the IV stand
2 seconds
Sitting down
On the back of the chair
20 seconds
4. Analysing RFID Data The RFID readers collectively provide a file containing the location, time and tag ID of each tag read. This data is both noisy and incomplete. Noise will be reduced by removing redundant reads and applying time filters [7]. We will initially address incompleteness by ‘estimating’ the presence of tags, using probabilistic approaches [3, 7]. If we can relate sequences of tag reads to activities or ‘motifs’, we may also be able to reduce incompleteness through ‘inference’ approaches [8]. We will produce a list of activities performed by anaesthetist by time. This will be used, alongside data from the manual anaesthetic record, and IDAS’s automated anaesthetic record, to triangulate with the activities recorded by the observers. Any differences will inform further refinement of our algorithms for reducing noise and incompleteness.
5. Conclusion Observing anaesthetic activity is challenging. There are long periods where little happens, punctuated with bursts of intense action. These bursts often involve a convergence of people and equipment, potentially obstructing the observer’s view. Thus there is some value in automated monitoring tools, always recording, placed at key locations, but posing minimal obstacle or distraction to the anaesthetic workflow. Our work so far has identified RFID equipment that seems suitable for such automated monitoring. But there is still a good deal of work ahead in learning how best to translate the RFID data into an accurate record of anaesthetic activity.
6. References [1] [2] [3] [4] [5] [6]
[7] [8]
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