Friday, June 29, 2012

Help For Cardiac Arrest Patients – Fast And Without Electricity

Textile cooling pads are to be used in future to prevent neurological damage after successful resuscitation. The system developed by scientists from the Hohenstein Institute in Bönnigheim requires no electric power, making it ideal especially for first aid in case of cardiac arrest.

Example of person on textile cooling pad
Credit:  Hohenstein Institute 

For what can be done when for example a traveller collapses on a bus, train or aeroplane? Every year, 375,000 people suffer a cardiac arrest in Europe alone. The heart suddenly starts beating uncontrollably, the pulse becomes irregular. Within a few seconds the patient becomes unconscious and breathing and heartbeat stop. For those affected, every second counts from this point on, because the patient's chances of survival decrease by ten percent with every second that passes until reanimation. 

Defibrillators have now become mandatory in public buildings and public transport. They use electric shock to restart the heartbeat. For most cardiac arrest patients, however, even successful reanimation is merely a partial success – only a few patients survive this life-saving measure without consequential neurological damage. This is due to parts of the brain possibly sustaining lasting damage caused by the lack of blood flow and oxygen supply during the period until the ambulance arrives. This often results in the affected becoming invalid.

Functional principle of zeolite/water
Credit:  Hohenstein Institute 

To avoid this type of brain damage in future, scientists from the faculty of Hygiene, Environment & Medicine at the Hohenstein Institute have developed a new therapy method for first aiders. In the framework of a research project supported by the state of Baden-Württemberg for the competition 'Biotechnology and medical technology', the scientists lead by Prof. Dr. Dirk Höfer developed the prototype of a textile cooling vest. The new type of medical product promises improved acute treatment for cardiac arrest by very quickly cooling down the patient's body.

It has been known for a long time that cooling can protect the brain against the dreaded oxygen deficit during a lack of blood flow. Targeted lowering of the temperature inside the body to 32 °C to 34 °C has been proven to protect the brain against irreparable neurological damage. This simple but extremely effective therapy principle was used by the Hohenstein scientists. They started by developing water-proof and absolutely airtight textile hollow fabric – so-called cooling pads. These were equipped with appropriate connection options and integrated into a vest. 

The new cooling pads consist of a water-proof and vacuum-tight textile hollow fabric and are connected to a metal container under vacuum pressure. The container is filled with a special mineral (zeolite). When an interposed valve is opened, the water in the pads instantly cools down to almost freezing.
Credit:  Hohenstein Institute 

The cooling pads are connected to a metal container under vacuum pressure containing a special mineral (zeolite). When an interposed valve is opened, the water in the pads is instantly cooled down to nearly freezing (see info box), very effectively draining body heat from the patient's body at the same time. The cooling system based on zeolite/water adsorption technology has a simple design and allows drastic lowering of the core body temperature after occurrence of a cardiac arrest at any time and in any place – without electric power! In future the self-sufficient cooling pads are intended to complement mobile defibrillators (with automated ECG analysis) for use by first aiders without medical knowledge e.g. in public buildings and public transport. For patients with cardiac arrest this means a much better chance of sustaining only minor consequential damage.

With this product the Hohenstein researchers have managed to develop a new non-invasive method for surface cooling of the body. That means no surgical procedure is required and in contrast to conventional cooling systems it can be used directly at the place of emergency without any power source. “The cooling pads harbour enormous potential in the neurological rehabilitation after cardiac arrests”, explains Prof. Dr. Dirk Höfer. “In addition to the benefits for the affected individual, every prevented case of invalidity is also a great financial advantage for the general public.” Even though the researchers are looking for an industrial partner for production and sales of the cooling pads for the time being, they are already contemplating other innovative applications for textile cooling and heating processes in medicine.

Zeolite/water adsorption technology
Zeolites are natural silicate minerals. Under vacuum they have the property of adsorbing polar molecules such as steam. Evaporation enthalpy significantly cools down the remaining water within a few minutes. The process of cooling generation can be activated at any time by opening a valve and continues until the zeolite is saturated with steam.

Brain damage from lack of blood flow
A number of harmful reactions are triggered when the brain does not receive enough oxygen as a result of a circulatory problem (ischaemia). This includes e.g. the formation of free radicals and toxic metabolism products. Targeted lowering of the core body temperature to 32 °C to 34 °C has been proven to protect the brain against irreparable neurological damage. In medical terms this form of therapy is referred to as 'therapeutic hypothermia' and it is used as a standard treatment in hospitals in the form of cooling blankets and cold drip solutions. 

Outside of intensive care units, however, especially at emergency sites, therapeutic hypothermia has not been applied until now. That means that precious time passes between receipt of the emergency message until arrival of adequate help at the site of emergency (rescue time in Baden-Württemberg: 10-15 minutes). The early time window directly after occurrence of the circulatory disturbance is therefore crucial because studies show that tissue damage is directly proportional to the duration of the lack of oxygen. The earlier heart attack patients are cooled down, the better therefore their chances of survival and the greater the possibility of full recovery.
Contacts and sources:
Hohenstein Institute

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