Compression Lows

This may be a new opening of an old wound. I have seen and heard of COMPRESSION LOWS rearing its ugly head this fall. I am trying to wrap my head around the term and what is happening in the body. Does this seem like a good description?

BACKGROUND: Compression lows are caused by the person’s body pressing against the mattress, pinning the CGM sensor/transmitter (CGM) between the person’s body and the mattress during sleep. First, the interstitial fluid (IF) is the fluid around body cells. Most of the time IF is exchanged with fluids in the blood vessels. During this exchange, IF glucose is enriched and cellular waste products are removed from the IF all over the body.

THE PROBLEM: When a person is in sound sleep and is mashing the CGM into the mattress, the IF is also mashed. It is this mashing or compressing of the IF that causes the IF not to exchange as it normally does. Since the cells around the CGM sensor wire continue to consume (eat) the glucose available in the compressed area around the sensor wire the glucose in the area drops.

OBSERVATION: It is this low reading in the CGM data is usually seen as a nearly level data graph and then a sudden drop of the glucose level. Because it is a low brought about by the pressure on the CGM, the term COMPRESSION LOW has been offered in pumping circles. Because the Compression Low is a low glucose only in the area of the CGM, a finger stick performed in response to a LOW alarm will show NORMAL. The variation between the finger stick and the CGM data leads to frustration and bewilderment, believing technology is the source of the error.

The next observation is the blood sugar measured by the CGM will return to a value near where the CGM line was before the drop in CGM value. The near level line, the drop & alarm, the finger stick of different reading, and the return to the near pre-alarm value is the full picture of the COMPRESSION LOW.

I would really like to get feedback. Thanks all.

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Ihi @987jaj yes, I think this sums it up. my only comment is this: if the CGM is supposed to indicate blood sugar, then the device, or the technology, IS the source of the error in a compression low. If you fully understand that IF is an analog, that the sensor in IF is accurately reading IF then the source of the error is the difference of the IF and your actual blood glucose. That would mean the device (the technology) is accurate but the IF analog is no longer proportional to blood sugar. Semantics? I think so but I’ve had a long week, doing battle with both my quality department and my technology department (not in the CGM industry, but in pharma) and this is about all the strength I have left. Cheers!


My comments J @987jaj tend to run a path similar to @Joe’s; not a device malfunction but rather the body “not delivering” substance that the CGM sensor needs to accurately perform. Put another way, insufficient IF [interstitial fluid] around the sensor wire, or IF that has for some reason been exhausted of glucose - must probably, that body muscles needed glucose feeding.

This CGM occurs [at least with Dexcom G6] for reasons other than compressing the sensor while with pressure while sleeping; at least in skinny guys like me during of following activities. I’ve had some really interesting conversations about this with technical people at Dexcom and at Tandem. Dehydration may be a cause for the sudden drop in IF glucose level.

An example: today as I completed my usual five mile morning walk, my CGM was reading a wonderful 108 mg/dl; this despite “Exercise Mode” which targets 140mg/dl being set on my t-Slim for two hours. Yes, I drank my usual 20 ozs. of Gatorade [not the 0 sugar stuff] while walking. I made my usual notations in my notebook, and began lunch preparations; did a 20 minute pre-eating bolus, set up my outside lunch station and saw my CGM reading at 84. Washed my hands, made lunch and before my sandwich finished toasting, my device was sounding “emergency” and CGM reading 54 mg/dl. The “glucose drop” from 108 to 54 took about 20 minutes - actually my glucose didn’t drop.

The G6 realizing something was wrong, ceased operation - “sensor error”, with no readings for 20 minutes; upon resumption of G6 readings, my BGL was displayed as 101 mg/dl. The glucose reading device did not malfunction, my body was the culprit.

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On very rare occasions I’ve gotten a “sensor error” alert. I called Dexcom the first time after switching out my sensor, and had them send a replacement. They told me to wait next time before calling (I don’t recall how long of the top of my head) to see if it resolved, and the couple of times sense then I have, and it came back. I didn’t know why it didn’t but I’ll keep this in mind. Thanks!

Dorie @wadawabbit, there are other reasons for "sensor error " readings, and the display will read " — ". These are almost normal; when these readings are presebt, the Dexcom display, on phone or receiver, will tell you to wait three hours before calling Dexcom.

What iwas describing is a sudden dropping of readings, one distinguished from compression. I have documented for Dexcom research precipitous reading changes of more than 75 mg/dl in less than a 20 minute period. Thankfully, this only happens a couple of times a week.

Thank you. I’ve gotten those annoying "Wait 3 hour dashes a few times - usually less than 3 hours before I’m planning to go to bed unfortunately :tired_face:, so thankfully they’re rare. The possibility of dehydration is one I should keep an eye on as I don’t drink as much water as I should so that’s helpful to keep in mind as a possibility - one of many.

@joe, @Dennis, @wadawabbit.

Did I just hit a hornet’s nest with a stick on this one about COMPRESSION LOWS???

Not sure, but I did learn a bit myself.

Not at all @987jaj. It looks like “figuring it out” to me. Aiming for understanding is never bad.

Actually J @987jaj you posted a Topic, with your good observation, that could be of interest and learning fir many members/readers of this site. I found your presentation to be accurate and well-stated; what I added is another instance where the G6 [I don’t recall this happening with G5], with its 30 minute “anticipation/prediction” could cause apprehension for users.

I’m hoping to hear from others on this topic. Over the years, listening to others, I’ve heard instances if “one-size-fits-all” doesn’t apply to TypeOne.