Enabling 24-hour wear |
monitor selection
waterproof
monitor heat sealed (P200-C heat sealer [Packer, Essex, UK] ) within Layflat plastic tubing (75mm wide x 150m long x 250 gauge [Packer, Essex, UK]) to eliminate reasons why the monitor may be removed (e.g. bathing, swimming)
Opsite flexifix [Smith&Nephew, London, UK] waterproof dressing placed over the sealed monitor
reduce chances of skin irritationappropriate materials used: hypoallergenic adhesive pad (PALstickie [PAL technologies, Glasgow, UK]), medical grade waterproof dressing (Opsite flexifix); food-safe plastic tubing (Packer layflat tubing)
enhance comfort
hypoallergenic adhesive pad (PALstickie) provided padding between the skin and the monitor/waterproof tube, and reduced the likelihood of skin irritation
edges of the waterproof pouch trimmed with some to spare, to avoid hard corners which might dig in the skin
schedule appointments to avoid removal
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Minimising Data Loss |
test all monitors before starting data collection
all monitors tested (we had 4 researchers wearing 13 monitors per leg) for multiple days before using them for data collection
monitors that were not functioning correctly identified and sought assistance from manufacturer
set minimum battery level for programming
use wide programming times
programmed to start recoding immediately, to allow confirmation that the monitor was collecting data (flashing green light)
programmed to record for 14 days (minimum required for full data collection was 9 days) to allow for delays in starting to wear the monitor
trained staff applied the monitor
ensured the monitors were applied appropriately
ensured waterproof dressing was applied properly, minimising potential for water ingress (and consequent data loss through removal or monitor stopping)
used a checklist on application, including re-checking monitor was recording data (flashing green light)
common misunderstandings/procedural shortcuts were pre-identified and addressed in training (e.g. highlighting tips and errors).
communication between participants and research staff
communication between central experts and fieldworkers
key diagnostic data logged by staff applying/removing the monitor, for example battery level at programming and downloading, whether green light flashing at application.
key diagnostic data recorded centrally (on a secure cloud server) allowing easy review by all staff
data recorded to increase compliance and allow identification of systematic errors/deviation from protocol and monitor malfunction
member of staff with experience of data collection using the monitor assigned to triage technical issues with using the monitor
early and continuous quality assurance checks allowed identification of individual and systematic deviations from protocol, immediate feedback to staff, and engagement in process
reducing opportunities to lose monitormonitor removed by researcher, which reduced reliance on participants for data retrieval, for example remembering to bring monitor to appointment, losing the monitor while not worn, accidentally washing monitor placed in pocket.
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Quality Assurance |
increasing confidence monitor was worn
monitor removed by researcher, allowing confirmation monitor still worn after end of analysis period
a message was provided to participants that monitor should not require re-attachment during data collection. Additional material to allow reattachment was not provided. Participants were not asked to prospectively record if monitor was not worn
assurance that monitor had not been reattached by participant was provided by using attachment materials that are not commonly available to participants
In the case that the monitor was removed by participant prior to research appointment, we then asked retrospectively for date and time of removal. This was close to date of removal to allow for reasonable recall, and was then checked with data record. Data processing was from midnight-midnight and not from specific time of removal, so day/date of removal was sufficient information
data inspection
routinely performed by a single researcher close to time collected; difficult cases resolved by discussion with a second researcher
hierarchical review process was used (weekly graphical display, daily graphical display, raw acceleration data), to speed up routine cases but maintain in-depth review when required.
conducted with confidence that monitor was on the leg during data collection (i.e. looking for issues in battery/monitor failure, or thresholds not appropriate, e.g. known not to collect shuffling gait at slow speeds)
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