Source: Annual Congress 2002 - Airway obstruction measurement (FOT - NEP) sleep and lung sound analysis
Disease area: Airway diseases

Abstract

Breath sounds at the chest wall are thought to originate from turbulent airflow in larger airways. If this is the case there will be a time-delay between the sound reaching the tracheal and chest wall microphones. As tracheal sound only occurs when airflow is over 0.3L/s sound may theoretically occur at the chest wall before the trachea (e.g.if generated in smaller airways at lower flow rates). We have timed the onset of inspiratory sounds (between 80 and 400Hz) at the trachea and at 14 sites over the chest wall using a Stethograph multi-channel recorder in 6 normals (mean age 40.8 range 21-53 yrs, 4 males) and 6 patients with COPD (mean age 58.7, range 49-65, 5 Males, FEV1% mean 0.99L range 0.6-1.48L). Sounds were recorded during deep breathing over 20s (Normals mean 5.17 breaths, range 4 to 8 and COPD mean 3.83 breaths, range 2 to 6) and the onset of inspiration calculated automatically when the signal rose 20% above baseline. In Normals the mean inspiratory onset at chest wall was -0.01s and in COPD -0.14s earlier than trachea (P<0.01 ) and the mean % of inspiration that occurred before the tracheal sound was -0.24% in normals and -10.94% in COPD (P<0.004). In 4 normals the readings were later than trachea in the lateral microphones (ie furthest away from the trachea). In the COPD patients there was a trend in the relationship between earlier onset of breath sounds and lower FEV1 (p NS). These results suggest the breath sound origin at the chest wall is not the trachea but more distal sites where turbulent flow is induced at lower flow rates. The difference between Normal and COPD is likely to be associated with the increased inspiratory flow resistance in COPD. This observation may also help characterise COPD acoustically.

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Citations should be made in the following way:
D. Barr, S. Jack, N. Duffy, J. E. Earis (Liverpool, United Kingdom). Acoustic mapping of the timing of inspiratory breath sounds in Normal subjects and patients with COPD. Eur Respir J 2002; 20: Suppl. 38, 328

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