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Monitoring in Diabetes 329

come available. and iPhones. This more accessible data, allows the
opportunity to set alarms for high and low blood
These capillary blood glucose level electronic meters, glucose levels, and for the sharing of results. The
with the use of lancet devices to pierce the skin have Dexcom 5 system for example has a facility to do
therefore become the typical self-monitoring modal- this and to also upload to a ‘cloud’ and so make the
ity used in most patients, who need to do this. The data available to other users, such as medical staff,
frequency and timing of these measurements, again to allow further manipulation and adjustment of ther-
being tailored to the individual, and their needs.
apy and other parameters to help improve glycaemic
Continuous glucose monitoring systems (CGMS) control further, or to look at changes to help reduce
have more recently become available, with the first detrimental aspects such as hypoglycaemia.
devices available from 2006. These devices rely on Sensors such as the Medtronic Enlite glucose sen-
insertion of a sensor through the skin to measure sor, can also link into insulin pumps, and allow for
subcutaneous or interstitial fluid, which is used as a potential closed loop system, so also looking to
a measure of the equivalent blood on capillary glu- improve glycemic control.
cose levels, allowing for more frequent if not contin-
uous testing, to filling gaps between the single point It should however be remembered that subcutaneous
measurements taken using capillary blood glucose or interstitial fluid measurements are not the same as
monitoring systems. These systems typically mea- capillary or venous measurements, with a delay of
sure glucose levels every 5 minutes, so giving almost 5 to 20 minutes often quoted between the capillary
290 single measurements each day, to allow better and interstitial result. If a patient therefore feels they
understanding of any trends or patterns in blood glu- are experiencing a hypoglycaemic episode, capillary
cose level over time. The initial devices, stored data blood glucose testing is a better way of knowing
over the lifetime of the probe, typically a few days, whether they are, than CGMS, although the latter
which could then be downloaded and analysed, and could give them an idea of the rate and timing of
if reviewed in conjunction with the patient completed any change in their blood glucose levels. This may be
diary, used to suggest any changes needed in thera- particularly useful the nocturnal and daytime hypo-
py. These are sometimes called ‘blinded’ CGM where glycaemic episodes, when hypoglycaemic awareness
data is saved for subsequent clinic review and not is not present. Several systems also require capillary
visible to the user, compared to ‘real time’ for open blood glucose measurements the calibration, al-
CGM where readings are provided on demand the though the latest generation sensors are reach the
patient who can use them to adjust their treatment. point where calibration measurements are not rou-
tinely required.
More recent systems, include Flash Glucose Mon-
itoring Systems, such as the Freestyle Libre, from A further advance in CGMS is the use of implant-
Abbott, which was launched in the UK in 2014, al- able sensors, that concurrently last up to 90 days,
though is not currently an NHS available product. such as the Ever sense CGM system, which has an
This has a topical disposable sensor, which is in the implantable sensor inserted under the skin, as a mi-
form of a patch which is stuck onto the skin, in which nor procedure with local anaesthetic, and an external
is found a sensor, which collects data of glucose lev- removable, rechargeable and water resistant smart
els in interstitial fluid, with 8 hours of data kept on transmitter, which can then be placed over the sen-
the sensor. This patch also contains a transmitter to sor. This transmitter can be set to vibrate for alerts.
allow this data to be collected onto a separate hand- The sensor receives its power / charge from the
held receiver, which is similar in size to many of the smart transmitter, and will not measure blood glu-
currently used capillary blood glucose meters on the cose levels when the transmitter is not being worn.
market. Data can be examined either on this hand- The transmitter uses Bluetooth technology to trans-
held device, or downloaded onto the PC if needed.
mit data collected to a smart phone for a more de-
Improvements in HbA1c, have been reported with this tailed evaluation of glucose levels. A 150 day version
type of monitoring, when compared to capillary blood of the sensor is potentially due for release in the near
glucose testing, but its current limited availability due future. The smart phone display allows the user to
to the need for self-funding may limits its usefulness look at rate and direction of change in glucose levels,
in our centre. and provides alerts when glucose approaches low or
high levels. Projective alert algorithms can also be
Newer devices on the market, also now include Blue- used to give advance warning of high-powered hy-
tooth technology which allows these devices to be poglycaemic events as well.
linked into compatible smart devices, such as iPads

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