PURPOSE: To determine if time based parameters of lung sounds differed in patients with chronic obstructive lung disease (COPD) as compared to normal subjects and patients with other disorders.
METHODS: A 16-channel lung sound analyzer (Stethographics Model STG1602) was used to collect 20s samples of sound from patients with COPD (n=103), normals (n=379), pneumonia (PN, n=118), congestive heart failure (CHF, n=92), bronchial asthma (n=62), and interstitial pulmonary fibrosis (IPF, n=39) during deeper than normal breathing. The ratio of sound energy from 20Hz to 80Hz to that from 80Hz to 800Hz was calculated (R4) in each patient.
RESULTS: The mean R4 in the left and right lungs are presented in Table 1. Notice that R4 was significantly greater in COPD (p<0.05).
CONCLUSION: The mechanism of the increased R4 in COPD is unknown. A possible explanation is that it may be due to the relatively increased size of the air spaces in the lung of COPD patients as we have noted a similar increase in low frequency peaks in patients with pneumothorax and pneumonectomy as well in a patient with a giant bulla.
CLINICAL IMPLICATIONS: A long-term goal of studies with multichannel lung sound analyzers is to provide useful diagnostic information at the bedside. The increase in low frequency peaks together with other features of COPD, such as decreased amplitude of sound and relatively prolonged inspiratory phases can help provide evidence that COPD is present. This can be done using a simple test using that requires little patient cooperation.
DISCLOSURE: Raymond Murphy, Grant monies (from sources other than industry) Supported in part by grant from NIH SBIR (1R43HL70480–01); Grant monies (from industry related sources) Supported in part by grant from Stethographics, Inc.; Shareholder Dr. Murphy and Dr. Vyshedskiy have financial interests in Stethographics, Inc.; Employee Dr. Murphy and Dr. Vyshedskiy have financial interests in Stethographics, Inc.; No Product/Research Disclosure Information