Sensor Warns Patients in Advance of Asthma Attack

By analysing patients' breath, a new Siemens sensor can tell hours in advance if someone will get an asthma attack. The gas sensor registers if an asthma sufferer's air passages are about to become inflamed, enabling the patient to take anti-inflammatory medication in time to prevent an attack. The sensor measures amounts as small as 1 ppb, making it as sensitive as larger devices that are far more expensive and not portable. 1 ppb corresponds approximately to the dilution of a cube of sugar in a 50- meter-long swimming pool. The new sensor is contained in a prototype device that will be portable and only a little larger than a cell phone.

In patients suffering from asthma, the latent inflammation of the bronchial tubes generally spreads long before the patients actually feel anything. If the inflammation is intense, the air passages constrict and the patient has an asthma attack. The attacks can be so serious that the patient has to be treated in hospital, which is why many asthma sufferers regularly take anti-inflammatory medication. Previously, the only way to detect impending asthma attacks in advance was to conduct expensive pulmonary examinations to determine if the patient's breath contained heightened levels of nitrogen monoxide (NO), which signal such an attack. By contrast, the new sensor from Siemens will enable patients to analyse the NO in their breath themselves. As a result, they will be able to take the minimum amount of preventive medication and increase the dose only if really necessary.

The new sensor can detect increases in NO one day before an acute asthma attack occurs. Over the past few years, medical researchers and health insurance companies have recognised that NO levels are an effective indication of an impending asthma attack. In the analysis of a patient's breath, the system first converts NO into nitrogen dioxide, after which the air flows across the actual sensor. Only the particles signaling the attack adhere to the sensor's surface. This generates a voltage that is measured by a field-effect transistor. The intensity of the voltage is directly dependent on the amount of NO in the patient's breath. On the basis of this value, the patient can decide what dose of anti-inflammatory medication he or she should take.