The “sniff” test: A surprising tool for coma prognosis

On Behalf of | Jan 9, 2024 | Motor Vehicle Accidents

After a wreck or another accident leaves someone in a coma with a severe head injury, the most important question their loved ones usually have at first is, “Will they wake up?”

When it comes to assessing the prognosis of coma victims, however, medical professionals have found that even the most careful clinical observations and the best imaging studies still didn’t provide an accurate answer to that question. Yet, a very simple tool, known as the “sniff” test, may provide clarity.

What is the sniff test, and why is it important?

A coma is a profound state of unconsciousness that leaves the victim broadly unresponsive to external stimuli. The sniff test involves exposing patients to pleasant and unpleasant odors and watching the response (or lack of one) in their breathing. 

The olfactory nerve, which is responsible for a patient’s sense of smell, connects directly to the brainstem. The brainstem is what regulates their basic bodily functions, including breathing. It’s also the base of consciousness. When the olfactory nerve is stimulated enough, the brainstem should have a response. 

During the test, the patient is observed to see if their breathing gets shallow when they’re exposed to putrid smells or deepens in response to pleasant ones. A positive response indicates that the patient’s brainstem is still functioning, at least to some degree. That indicates that the patient is most likely to regain at least minimal consciousness.

This is useful because it can give doctors:

  • An early prediction: Since it is quick and easy to perform, it can be done relatively early in the coma, allowing for faster insights into the patient’s potential for recovery. This can help the physicians tailor their treatment plans.
  • A better way to guide families: The response to the sniff test can also help doctors give the families of coma patients some real clarity in the days and weeks following an accident. That can help them adjust to the reality of their situation better and make informed decisions about the future.

If your loved one suffered a traumatic brain injury and is in a coma after a wreck with a semi or in some other accident, it is always wisest to find out more about your legal options.