What is a SCRAM Bracelet?

During a Los Angeles court hearing this morning, actress Lindsay Lohan was ordered to wear an alcohol-monitoring bracelet, called a SCRAM device. In legal cases involving driving under the influence, or DUI, the use of a SCRAM bracelet is not unusual to ensure abstinence from alcohol either while the case is pending or as a term of probation.

Alcohol Monitoring Systems, Inc patented the SCRAM device, which stands for secure continuous remote alcohol monitor. It is worn on the ankle and measures the subject’s blood alcohol level through perspiration on the skin. The measurement of transdermal alcohol content is converted into a blood alcohol level.

Several studies have shown that there is a good correlation between the amount of alcohol in the bloodstream and that which is contained in the perspiration. Alcohol, specifically ethanol, has an affinity for water, so it is rapidly distributed throughout the body. The body fluids, including perspiration, will therefore contain a level of alcohol as a proportion of that in the blood.

However, the downside is that the amount of alcohol present in perspiration can vary based on a number of factors, such as the thickness of the skin, the amount of sweating, and cutaneous blood flow. Therefore the device cannot be used to accurately measure the amount of alcohol in the bloodstream, only its presence. This makes the bracelet a good screening tool for abstinence, but not a device to judge level of intoxication.

The SCRAM bracelet takes readings every 30 minutes and communicates with a home-placed modem via radio signal. Should the bracelet be tampered with, a monitoring agency will alert authorities.

One problem with the bracelet, however, is that it is non-specific for beverage alcohol. Other types of alcohol, including that from products such as hairsprays or perfumes, may inadvertently be measured by the device.