ATS: New Device May Aid Pneumonia Diagnosis

By Mike Fillon
Special to DG News

ATLANTA, GA -- May 24, 2002 -- A new device that employs lung sound analysis may provide improved and objective evidence supporting the diagnosis of pneumonia.

Results of a clinical study using the Multi-channel STG System were presented at ATS 2002, the American Thoracic Society's 98th International Conference. The device, worn like a vest and employing a 16-channel lung sound analyzer, was recently approved by the Food and Drug Administration (FDA) in the United States.

A convenience sample of 51 patients at Faulkner Hospital, in Boston, Massachusetts - a community teaching hospital - who had a clinical diagnosis of pneumonia and 51 normal subjects were examined with the sound analyzer. An Acoustic Pneumonia Score (APC) was generated based on individual acoustic findings detected by the system including rates of wheezing and rhonchi, automatic counts of fine and coarse crackles as well as amplitude measurements of inspiration and expiration.

The researchers found inspiratory crackles were present in 88 percent of these patients as compared to only 22 percent in the normals. Expiratory crackles were also more common - 59 percent as compared to 6 percent.

Also, wheezes and rhonchi were more common in the patients with pneumonia; 37 percent had wheezing or rhonchi in inspiration and 47 percent in expiration as compared to 2 percent and 0 percent respectfully in the normals.

According to Ray Murphy, MD, who developed the device, the STG System provides lung sound information in three ways. First, the recorded lung sounds are displayed in a time-expanded waveform, which allows visual examination and audio playback of the data. The display of the traces, similar to an EKG, allows direct visual detection of the abnormalities. "Each channel can be examined for crackles, wheezes, and irregular patterns of inspiration and expiration," said Dr. Murphy.

Second, the computer automatically analyses acoustic energy versus time and detects crackles, wheezes and rhonchi. Derived measures of the sound characteristics are displayed on an anatomical diagram to allow visualization of the spatial distribution of lung function and abnormalities. Further information on the overall amplitude of breath sounds, timing of the abnormalities, and crackle and wheeze counts is included in this display. "Differences in abnormal patterns among different diseases become apparent in this context," said Dr. Murphy. He notes that the method is noninvasive and easy to perform even in severely ill patients.

The study was funded by Stethographics, Inc., a company founded by Dr. Murphy.

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