@RMcM, @Dennis, @joe
I was asked to put something together about COMPRESSION LOWs recently. Here is what I pulled together along with an article from the US National Library of Medicine.
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.
Here is a link to Susceptibility of Interstitial Continuous Glucose Monitor Performance to Sleeping Position
Hope this helps.