Patients exposed to brain injury to a range of odor may determine whether they will recover, according to researchers behind a & # 39; sniff test & # 39; study.
Researchers at Cambridge University presented patients with odors, including shampoo and rotten fish, then monitored their reactions through a nasal tube.
In the new study, researchers saw patients with brain damage who were very poor if there were no signs of awareness of & # 39; a world to show them.
All patients who did not respond to a sniff test went on to raise their awareness with more than 91 percent who were still alive three and a half years after their injury.
The inexpensive and simple test allowed doctors to determine precise diagnosis and treatment for patients with limited consciousness, the authors argue.
Researchers at Cambridge University presented patients with odors, including shampoo and rotten fish, then monitored their reactions through a nasal tube. Stock image
Lead author Dr Anat Arzi, of & # 39; Cambridge University, said the accuracy of & # 39; e sniff test was remarkable.
It is often difficult for doctors to determine the state of consciousness of a patient after a severe brain injury and errors in diagnosis are made in 40 percent of cases.
A patient who is minimally conscious is different from someone in a vegetative state and their future outcomes are different.
An accurate diagnosis is critical in order to inform the treatment strategies such as pain management and can influence end-of-life decisions.
Professor Noam Sobel, of the Weizmann Institute of Science in Israel, said that feeling of smoke is a & # 39; very basic mechanism & # 39; is that you don't trust structures deep in your brain.
& # 39; The brain automatically changes the way we sniff in response to various smells, & # 39; said Sobel, who was a lead author on the study.
& # 39; For example, when presented with an unusual scent, we automatically take shorter, shallow breaths.
& # 39; In healthy people, the snoring reaction occurs both in waking and in sleeping states of consciousness. & # 39;
Scientists have conducted their research on 43 patients with severe brain injury.
The experimenter first explained to each patient that various odors would be presented to them and the breathing through their nose would be checked with a small tube called a nasal cannula.
Researchers had no indication if the patients had heard or understood.
Next, a pot with a pleasant smell of shampoo, an unusual smell of rotten fish as well as no odor was presented to every patient for every second.
Scientists use a deep mechanism in the brain to conduct a & # 39; sniff test & # 39; to make
Our sense of smoke is a core and basic mechanism – it depends on structures deep in the brain.
In fact, the brain automatically changes the way we sniff in response to various smells.
For more unpleasant smells, such as rotten fish, we take shorter, shallow breaths.
Researchers used this mechanism to do their sniff test in patients who could not respond in any other way.
They presented patients with a smell in a jar with a nasal tube.
The team then measured how much air the patient sniffed into their nose.
Study author Dr Yaron Sacher of the Loewenstein Rehabilitation Hospital in Israel said that each jar was presented ten times to the patient in a random order.
They then took a measurement of the volume of air sniffed by the patient.
Minimally conscious patients inhaled significantly less in response to smells, but did not distinguish between nice and annoying smells, it appeared.
Patients have also changed their nasal airflow in response to the jar without smoke, suggesting awareness as a learned anticipation of a smoke.
Patients for vegetative state varied. Some did not change their breath in response to any of the odors, while others did.
Scientists later found 91 percent of patients who received a prompt response shortly after an injury, still three and a half years later in a follow-up study.
While 63 percent of those who did not show an answer had died.
The researchers were able to measure how well deep-seated brain structures worked by measuring the cord response in severely brain injured patients.
All patients who did not respond to a sniff test – from both shampoo and rotting fish – continued to regain consciousness with more than 91 percent still three and a half years after injury still alive. Stock image
Against the patient group, they found that sniff responses consistently differ between those in a vegetative state and those in a minimally conscious state, and provide further evidence of a precise diagnosis.
& # 39; We found that if patients in a vegetative state had a sniff reaction, they later transitioned to at least a minimally conscious state, & # 39; said Arzi.
& # 39; In some cases, this was the only sign that would heal their brains and we saw it days, weeks, and even months before other signs.
In a vegetative state, the patient can open their eyes, wake up, and regularly fall asleep and have basic reflexes, but they leave no meaningful answers or signs of consciousness.
A minimum conscious state differs, in order for the patient to have periods in which they can display signs of consciousness or respond to commands.
Dr Tristan Bekinschtein, of & # 39; the Psychology Department of & # 39; The University of Cambridge, said when the cord reaction normally functions, the patient may still show some level of consciousness, even if all other signs are absent.
& # 39; This new and simple method to assess the chance of recovery should be immediately included in & # 39; & # 39; diagnostic tools for patients with conscious disorders, & # 39;
The findings were published in the journal Nature.