A new algorithm being used in automatic external defibrillators could help cut deaths from cardiorespiratory arrests, such as that of professional footballer Christian Benitez

Algorithm to cut deaths from cardiorespiratory arrest

Deaths from cardiorespiratory arrests, such as that of professional footballer Christian Benitez, could be reduced by a new algorithm.

Benitez, who played 58 times for Ecuador and was one of his country's all-time leading goalscorers, died yesterday of cardiorespiratory failure after being admitted to hospital for stomach pains, according to his Qatari club El Jaish, who signed him only three weeks ago.

But a new algorithm capable of diagnosing heart rhythm with just 3 seconds’ worth of signal developed by researchers at the University of the Basque Country could help to cut the number of deaths from such incidents.

The team from the Signal and Communications Group of the Faculty of Engineering has demonstrated that the algorithm makes it possible to come up with a diagnosis as to whether an electric shock needs to be applied without stopping vital cardiac massage.

“We don’t save lives, we just do research,” Jesús Ruiz, leader of the team makes clear. “But what has been confirmed is that it is cardiac massage that saves lives.”

During a cardiorespiratory arrest it is essential to apply immediate and continuous thoracic compressions that ensure enough blood gets to the brain and the heart itself.

This is where the automated external defibrillator (AED) plays an important role. They are simple pieces of equipment that can be used by people with the minimum of training, and are common in airports, shopping centres and sports centres.

The devices analyse the patient’s cardiac rhythm and indicate to the person assisting whether they have to move away for an electric shock to be applied or whether they have to continue with the cardiac massage.

The problem is that the thoracic compressions lead to interference with the signal that the AED is picking up. As a result, the compressions have to be stopped so that the equipment can reliably diagnose the rhythm.

But, interrupting the compressions lowers the patient's chances of survival, prompting researchers to carry out work over the last 15 years to cut out this interference.

Current guidelines recommend stopping the compressions every two minutes to analyse the rhythm reliably. If the interference is cut out, it would be possible to make a diagnosis without stopping the massage.

“But if the device inappropriately tells you to stop, because it has picked up a defibrillatable rhythm, and it turns out not to be the case, you may stop the compressions for longer than what is advised in the guidelines,” explains Ruiz.

But in another article published in February in the journal Resuscitation, Ruiz’ group proposed an alternative to cutting out the interference – by taking advantage in the ventilation pauses to diagnose heart rhythm.

“The guidelines propose 2-minute cycles with intervals of 30 compressions, which are about 20 seconds, and 2 ventilations, which are 5 seconds. And the article shows, for the first time, that it is possible to take advantage of the ventilation intervals, in which there is no interference, to make a reliable diagnosis.

“That way we would have a reliable diagnosis every 20 seconds; much more efficient than what the rules state, which is every two minutes,” said Ruiz.

To be able to make a diagnosis in these 5 seconds, they have applied a rapid algorithm, developed by the group.

“While a normal algorithm takes 9 seconds' worth of signal to make a diagnosis, we have developed one that is very reliable and works with short signals. With the 3 seconds we can make a pretty reliable diagnosis,” said Ruiz.

This algorithm has now been introduced and is being sold in the R800 defibrillator produced by the company Osatu S. Coop. (Ermua, Bizkaia, Basque Country) with which the group has been collaborating for over 12 years.

Osatu is a small co-operative that designs, manufactures and markets AEDs and manual monitor-defibrillators under the brand name Bexencardio. In September they will be launching another two models equipped with the same algorithm.

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