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    « Continuous Monitoring: In a Sentence | Main | I Missed It... Because I Was Missing the Point »

    Guardian RT vs Paradigm REAL-Time System

    The Paradigm REAL-Time system really is the Guardian RT all grown up. My experience on switch day notwithstanding, I'd be lying through my teeth if I said it didn't have big advantages. A whole lot of advantages.

    But there is one major drawback:

    I can't hear it!

    The alarms on the Guardian RT are sirens, without understatement. Low or high alarms going off at night have woken people sleeping in the next room to me! Added to the fact that you can have 'beep' and 'vibrate' alerts simultaneously (and this is a hearty up-'n-at-'em shake-itself-onto-the-floor kind of vibrate) and you'd be hard pushed to ever miss an alarm or alert.

    In fact, I didn't.

    By contrast, the 722 alarms are very quiet. Even the vibrate is pretty mild, and there is no option to have both alert types simultaneously. Whereas the Guardian RT awoke me as soon as an alarm went off, the 722 has taken between 10 and 18 minutes to wake me up at night. Yes EIGHTEEN minutes. A fast moving low could do a lot of damage in that time.

    I'm still working on solutions to this, but it is early days yet, since I'm (fortunately) not getting many overnight alarms right now.

    It has led me to think about the names of the devices and I couldn't help but wonder whether the Paradigm REAL-Time System is simply more of a Real-Time monitor providing data, whereas the Guardian is just that: A Guardian. Something extra to watch over you and wake you from your sleep should the need arise. It is daft that there should be any difference in the use of the systems. But then, it strikes me as pretty daft that one should be so LOUD and the other so quiet.

    So, what are the other major differences?

    To begin with the obvious:

    Carrying one device vs carrying two

    Hpim1057 If you are using a pump and a continuous monitor it makes sense to try and combine them. Even leaving aside the bulk an unattractiveness of the Guardian RT monitor, to me it is a great advantage to only have one unit to clip to my clothing and carry around, one unit to worry about damaging or losing, one unit to explain to airport security personnel. And one unit that is the exact size of the pump I would wear anyway, no less.

    Trend Graphs and Trend Arrows

    722status_3 The graphs showing three hour and twenty-four hour trends are great. I'd got used to drawing a mental graph with the last dozen or so numbers from the Guardian RT, but to have it there on the screen without having to think about it is great. A word of warning though: the screen size is very small - the same as any other Paradigm pump. I think the samll size of the graph can give some false impressions about exactly how stable the glucose level is since a reading of 6 mmol is not that far removed from one of 9 mmol giving the impression of a much flatter line than may be there in reality.

    This in itself could be a reason for the inclusion of the trend arrows, but to be honest, I don't actually find them much use. Perhaps this is because I got used to mentally calculating the trend whilst using the Guardian RT, or perhaps it is because my levels have been pretty stable anyway over the last week (I have yet to see a double arrow, indicating a change of more than 2mmol in 20 minutes, in either direction). However, it strikes me that the trend arrows seem in themselves to be very much a response to single values, which is obviously ridiculous. They are basically a comparison of a pair of values taken twenty minutes apart. I've so far seen a down trend arrow when the current reading is actually higher that the previous one, and vice versa. Take the following as an example:

    15:40  7.1
    15:45  7.5
    15:50  7.2
    15:55  6.8
    16:00  6.2  *No arrow*
    16:05  6.4  *One down trend arrow appears*

    The arrow appears at 16:05 since this value is >1mmol less than the value recorded at 15:45, despite the fact that the reading has gone up since 16:00. No arrow appears for the lower reading at 16:00 since this is not greater than 1mmol different to the reading at 16:40. The biggest drop in this data series, between 15:45 and 16:00 is not considered as these two reading do not make a twenty minute pair!

    I'm not knocking trend arrows per se, I just think this feature could use a little more work to maximise its value!

    Calibration Warning

    Both the Guardain RT and the Paradigm REAL-Time System need to be calibrated by entering a fingerstick result a minimum of every 12 hours. On the Guardian RT, the time the next calibration is due can be accessed by pressing the up arrow once from the home screen, and the time and value of the last calibration by pressing 'SEL' twice from the home screen to get to the 'Meter BG' screen. The pump would also emit a small beep and/or vibrate at six hours since the last calibration/until the next one amd the word CAL would appear on the home screen. To be honest though, I got a lot of 'Enter BG' alarms where I had reached the 12 hour mark without remembering, and these were accompnied by a 15 minute skip in data.

    The 722 allows you to set a 'CAL Reminder Alarm' to alert you anywhere between 5 minutes and 4 hours before the calibration is due. It also records the date, time and value of at least the 28 most recent calibrations (my 722 currently has 28 values, but it may store more.) Remembering to calibrate is also easier since each time a blood glucose value is entered into the Bolus Wizard, to calculate a bolus dose, (so at least every time I eat) it asks you whether you want to use that value to update the sensor. Before anyone asks, yes, this is better than the pump automatically using it to update since calibrations performed when the blood glucose is changing rapidly tend to throw things out of whack.

    Sensor Restart

    If you haven't heard that extending the three day life of the sensors is possible, then this must be the first thing you've ever read about about CGM technology, bar the official company info!

    With the Guardian RT re-using an existing sensor requires treating the old sensor exactly like a new one. So you have to disconnect the sensor and transmitter, then search for the transmitter and then reconnect the two. Bingo! The monitor thinks your old sensor is a brand new one. Drawback? You have to wait for a complete two hour initialisation. Not only does this mean a gap of two hours in the data, but it also has to be timed so that you won't get woken up to input a meter calibration at the end of the initialisation, and ideally so you don't end up needing to calibrate soon after a meal when glucose levels might be unstable.

    Timing it would be easier if there was better warning of the sensor end time. If you don't make a mental or written note of the day and time of your last "new sensor" the Guardian RT will only warn you after you have entered a meter calibration less than 12 hours before the end of the sensor life. The screen which shows when the next calibration is due (see above) changes to 'Replace' with a time, when the 72 hour life will be reached before the next calibration is due. But if a Calibration isn't required or entered until 71 hours of sensor life has already passed, you could find yourself with only a one hour warning. And even then, it is a warning you have to seek out and check for yourself!

    With Paradigm REAL-Time System, you can restart the old sensor as a new sensor, and provided you don't disconnect the transmitter from the sensor first, it will be ready to begin giving data again in just 15 minutes. The fact that there is only a 15 minute gap in data makes it more acceptable to delay the restart if necessary, to wait until glucose levels are stable enough for a calibration. In addition, the exact life of the sensor is recorded in days and hours on the status screen, so you know exactly when it will need to be replaced.


    Synchronisation and Missed Data

    The Guardian RT accepts missing a single data value. This value is then retrieved along with the next value. If two successive points are missed, the Guardian RT will begin to search for the sensor. Provided it is found within five minutes, when the next data point is due, all three values are retrieved and recorded. Three data points seems to be the maximum the transmitter can store without passing them to the monitor, so a loss of synchronisation between transmitter and monitor of greater than 15 minutes causes a break in the data data. If the transmitter still is not found after 8 minutes, the unit will alarm with  'No Sync' alarm. It is then necessary to start another search manually, ensuring the transmitter and monitor are well within range.

    The Paradigm System, on the other hand, can accommodate much more missing data. You can select how long you want the unit to wait before alerting you to the loss of Sync, referred to now as 'Weak Signal' to between 5 and 40 minutes. I'm told, although I've yet to confirm this personally, that the unit can retrieve the full 40 minutes of data. This would obviously be a big plus in situations such as going swimming, as it would be possible to leave the unit well away from the water, but still look back at a full set of data later to see the impact of the swimming session.

    My experience over the lat week suggests however that the 722 tends to lose the signal more readily than the Guardian RT did. This is difficult to gauge exactly, since the 722 is for the vast majority of time attached to me by my infusion set and I'm unlikely to leave it very far away from me. The Guardian RT would quite happily continue to pick up data when I was actually in the next room, whereas the 722 will sometimes show 'Weak Signal' when I happen to have it on the opposite side of my body to the transmitter. It really isn't a great problem though. As I say, I'm unlikely ever to get that far away from the 722, and the fact that it picks up so much missed data is a definite plus. So far the only days on which I have not had a full set of 288 data points recorded at the end of the day are those when the sensor has been restarted. The Guardian RT, on the other hand, would often have gaps - including, of course, those where I forgot to calibrate on time!

    Snooze Features

    As I explained to Bernard here it is possible to turn both the high and low alerts on the Guardian RT off, as well as select the interval at which the alerts repeat to allow for the fact that both high and low levels take time to correct, and you don't want to be bugged by alarms every five minutes until you are back in range. That would be enough to test the patience of a saint! The Guardian RT also has the rather curious 'Snooze' feature for high alerts. This can be set independently of the repeat interval to prevent you being alerted to another high value for between one and twelve hours and applies only to high levels, not lows. I did use this feature a couple of times overnight, where I really wanted to get sleep and chose to chance staying on the high side for a little longer without being woken up if my first correction didn't fix things. Setting it was easier than going and changing the interval in the setup screen.

    On the Paradigm System this feature is gone. You can still choose to turn either or both the low and high alerts off and each one has what is referred to as a 'snooze', which is the same as the repeat interval on the Guardian RT. The 'High snooze' can be between 5 minutes (??! - Anyone discovers an insulin that works that fast to correct highs, send some my way will 'ya?!) and three hours. The 'Low snooze' can be set to between 5 minutes and 1 hour. If you want longer than that, you'd have to turn the alert off. I guess the advantage of the 'snooze' on the Guardian RT is that the alerts will resume themselves after the set time, rather like the resumption of basal delivery after a temp basal of 0.0 u/h vs remembering to restart the pump after a suspend.

    Transmitter Size

    Transmitters_1 Tiffany has written here about the problems of concealing the transmitter under fitted clothing and this isn't helped by the fact that the 522/722 transmitter is actually bigger than the Guardian RT transmitter. It is slightly bigger all round and, significantly, around 30% thicker. This may be extra waterproofing. It may reflect that extra data storage the Paradigm transmitter seems to be able to handle. It may also be explained by the fact that the transmitter now emits beeps when connected to or disconnected from a sensor, and so must contain some sort of speaker. Overall I think that if you're prepared to accept the size of the Guardian RT transmitter, the difference is not that big. I sometimes find the thicker profile more uncomfortable if I end up lying on it, but to be fair, the clothes issue is not a biggie for me as it doesn't seem to show, unless you're really looking, under any of my favourite outfits!


    The Guardian RT comes with 'Guardian Solutions' software, which enables you to download all the data from the Guardian RT onto your computer. There is nothing flashy about the software. It gives you a graph for each day, as well as a 21 day overlay (but no options for different numbers of days, or to restrict it to weekend or weekdays only, for example). Beyond the daily high, low and average reading, there are no other stats either. However, the graphs are extremely useful for spotting trends (See here for an example) even without any other statistical analysis.

    And I really miss those graphs right now.

    I don't currently have any way to download data from my 722 pump. This is partly because I still have it on loan, and was not given a download cable. However, even if I had the cable, I'm not convinced I could use it. The Medtronic Carelink web-based Therapy Management System is not available to users outside the US or Canada. But aside from Carelink, there doesn't seem to b any other software to use with the 722 - or at least Medtronic haven't been able to tell me that there is.

    I think this is a serious drawback. The on-screen graphs are great, but their small size limits their value, as does the fact that you can only see back to the last 24 hours, so you can't easily compare consecutive days, or any days for that matter, to spot patterns. Without the ability to manage all the information that continuous monitoring gives you, it loses so much of its value.

    So there you have it. I recognise that much of this information is probably somewhat redundant to people making a choice of monitoring system, as I understand that the new improved version of the Guardian RT - the Guardian REAL-Time System is about to become available. Since I still have decisions to make about my long term choice of system, I've been looking into this one with interest. So for the next instalment: Upcoming features of the Guardian REAL-Time System!

    And after that, an end to the obsession with CGM technology??!

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    Hey Caro,
    This is a great comparison! I also really appreciate the picture that you posted of the Paradigm RT sensor in comparison to the Guardian. It's interesting to see both the size difference as well as the cosmetic differences.

    FYI the x22 pumps will download data into Medtronic's Solutions software (for pumps), as long as it's the most recent software version. If you want, I can copy my CD and mail it to you; email me and let me know!


    GREAT POST! Between you and Tiffany writing about these details, I feel armed with enough information to approach my doctor at Joslin about trying one of these gizmos out. The benefit of being able to mark glucose trends is tremendous.

    I hope everything is going well. :)

    - kerri.

    Yes, very nice comparison - this information is very helpful. Even though all of the systems out are beyond my reach financially, I still like to keep up with the pros/cons, etc.


    Hi Caro, great post. I've using the MM 522 real-time since June, and have experienced the same issues with the alarm not being loud enough (especially when sleeping) as you have. A few things I've done (besides complain to MM!) to improve the situation: (1) attached the pump to the open end of my pillow using one of the clips MM provides with the 522/722, (2) used the vibrate mode alarm (under Utilities) whenever the pump is FIRMLY against my body, like when using the leather wrap-around belt case. And (3) when set for audible alarm (only) be sure to set it to long beeps. Hope this helps! Steve

    Could you please email me if you have experience with the continuous monitor and know if there is a limit as to how fast glucose can drop in an hour. For example can it drop more than 100mg/dl, more than 200?
    thanks, Margo

    How long can the sensor actually last?

    Adil, please see my answer to this question in a new post I put up today:


    Thanks for asking it!

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