Bedrock's shiverometer and active counterwarming technology allows Therapeutic Temperature Management (TTM) to prevent fevers and improve outcomes by dealing with the central problem of shivering.


Fevers cause secondary brain injury and worsen outcomes in patients with neurological critical illnesses such as ischemic stroke, intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), and traumatic brain injury (TBI). When a primary insult to the brain (like stroke or bleeding) has occurred, fevers can occur in the days following (either because of infection or often because of paradoxical reaction in the brain called central fevers). Because the injured brain tissue is sensitive to the rise in temperature, these fevers cause secondary brain injury  and worsen outcomes. 

Fevers worsen outcomes and increase the risk of death after neurological diagnoses like ischemic stroke, ICH, SAH, and TBI. 

Among patients with fever in the PAIS trial, administration of paracetamol (acetaminophen) [aka Tylenol] reduced fever burden on average by less than a third of one degree celsius but still improved outcomes after stroke. There was no effect of the drug in patients without fever. 

Preventing FEVERS improves outcomes 

By reducing the burden of fever by only a third of a degree celsius in the PAIS trial, the over-the-counter antipyretic drug paracetamol (acetaminophen) [well known by the trade name Tylenol in the U.S.] significantly improved outcomes among febrile patients with stroke.

Just giving an antipyretic drug isn't enough. Devices do a much better job of preventing fevers: 

Examples of several different TTM devices available on the U.S. market. 

Example of the temperature curve over time with fevers despite administration of acetaminophen (Tylenol), followed by complete fever suppression with a TTM device.

Therapeutic Temperature Management (TTM)

The modern practice of TTM is centered on fever prevention to try to improve outcomes after primary insults to the brain. Prevention of fevers after cardiac arrest using a TTM device improves outcomes:

Using TTM to induce hypothermia was first shown to be better than doing nothing and allowing fevers [Bernard and HACA trials, New England Journal 2002]. A subsequent large trial called TTM showed that there was no difference between normothermia (using the device to prevent fevers) and hypothermia (cooling below normal) [TTM, New England Journal, 2013], showing that the difference in outcomes is from fever prevention.

Compared to the very small number of patients surviving cardiac arrest each year in the U.S., the need for TTM in other neurological diagnoses is enormous.

Size of the Market for TTM in the U.S.

With fevers known to worsen outcomes in so many common acute neurological conditions like stroke, brain hemorrhage (ICH), ruptured aneurysms (SAH), trauma (TBI), and post-arrest, there is large need for wider use of TTM technology:


With such a large clinical need and so many devices on the market, why isn't TTM applied more often than it is? The major issue limiting the wider use of TTM is the problem of shivering

Shivering happens in TTM because the patient's hypothalamus (the center in the brain that controls temperature) is trying to cause a fever, but the TTM cooling device is doing its job and preventing this. The gap between where the hypothalamus wants the temperature to be and the actual (normal) temperature causes the hypothalamus to generate shivering in an attempt to heat the body.

Shivering causes several problems:

  • Shivering is very noxious to the patient: it is a source of major discomfort and distress.
  • Shivering fights the cooling process, making it harder to prevent fevers.
  • Shivering is very energy-intensive: when a patient shivers, this diverts critical energy resources away from the heart, brain, and the process of healing.
  • Nursing monitoring and treatment of shivering by requires intensive, hands-on nursing resources and attention.


Bedrock's shiverometer technology allows clinicians to directly and noninvasively monitor shivering by extracting electromyographic signal of shivering muscles from the surface ECG:

Schematic of lead placement for the electrical shiverometer, with an example of ECG measured from a shivering subject, showing the characteristic waveform of the ECG and the superimposed shivering EMG, which looks like 'noise' contaminating the ECG signal. 

Why USE a SHIVERometer?

Without automatic measurement of shivering, nurses and doctors have to monitor shivering during TTM manually, by observing the patient from time to time. The current standard of care for doing this is a simple three point scale (mild, moderate, or severe shivering) called the Bedside Shivering Assessment Scale (BSAS) that is typically administered once per hour, at most. 

Automatic measurement of shivering frees up critical nursing resources and allows for much more frequent assessments and detecting shivering earlier, before it becomes more severe and thus more difficult to treat with anti-shivering medications. Automatic shivering detection also enables Bedrock's active counterwarming technology, which uses feedback mechanisms to apply counterwarming measures selectively to suppress shivering when it becomes a problem:


The Bedrock shiverometer applies a patent-protected method to automatically extract and accurately quantify shivering EMG non-invasively from a patient's ECG (heartbeat) signal:

Steps involved in extracting EMG from the combined ECG+EMG signal measured using noninvasive ECG electrodes on the patient's chest. 

Read the Patent

For much more detailed information on how the shiverometer works, and about how active counterwarming works, click here to read the granted U.S. patent (Flint 2014, #8,706,207).