Published in the journal Nature, the study involved brain injured patients showing very minimal or no signs of awareness of the external world. It found that 100% of patients who reacted to the sniff test went on to regain consciousness, and over 91% of these patients were still alive three and a half years after injury.
“The accuracy of the sniff test is remarkable - I hope it will help in the treatment of severely brain injured patients around the world,” said Anat Arzi, a researcher in the University of Cambridge’s Department of Psychology and the Weizmann Institute of Science Israel, who led the research, together with Professor Noam Sobel from the Weizmann Institute of Science Israel and Dr Yaron Sacher from the Loewenstein Rehabilitation Hospital Israel.
It is often difficult for doctors to determine a patient’s state of consciousness after a severe brain injury. Errors in diagnosis are made in up to 40% of cases. A patient that is minimally conscious differs from one in a vegetative state, and their future outcomes differ. An accurate diagnosis is critical because it informs treatment strategies such as pain management, and can underlie end-of-life decisions.
Our sense of smell is a very basic mechanism and relies on structures deep within the brain. The brain automatically changes the way we sniff in response to different smells - for example, when presented with an unpleasant smell we automatically take shorter, shallower breaths. In healthy humans the sniff-response happens in both waking and sleeping states of consciousness.
Reproduced courtesy of the University of Cambridge