To determine the breath-to-breath crackle variability and also the influence of breathing effort on the crackle rate in patients with pneumonia (PN), CHF, and interstitial pulmonary fibrosis (IPF).
A convenience sample of 107 patients with PN, 70 patients with CHF, and 33 patients with IPF in a community teaching hospital were examined with a 16 channel lung sound analyzer (Stethographics, Model 1602). The Stethograph (STG) automatically identifies and quantifies number of acoustic parameters including the crackle rate (CR). All patients were instructed to perform several breathing maneuvers in the following sequence: normal breathing, deeper than normal breathing, cough several times and repeat deeper than normal breathing, vital capacity maneuver, and repeat deeper than normal breathing. Each breathing maneuver was recorded for 20 seconds. CR in each breathing maneuver was expressed in percent of CR during the “deeper than normal” breathing maneuver. Breath-to-breath crackle variability was assessed during the “deeper than normal” breathing maneuver and was expressed as percent of the total number of crackles.
In patients with PN, CR was lower during the normal breathing (73 ± 39%). CR did not change significantly following the cough (93 ± 74%) or vital capacity maneuver (92 ± 49%). In patients with CHF, CR was higher during the normal breathing (146 ± 93%), CR did not change significantly following the cough (120 ± 49%) or vital capacity maneuver (89 ± 32%). In patients with IPF, CR was higher during normal breathing (141 ± 81%). CR did not changed significantly after the cough (86 ± 45%) and after a vital capacity maneuver (93 ± 51%). Breath-to-breath crackle variability was relatively insignificant: PN = 27 ± 18%; CHF=27 ± 12%; IPF=23 ± 12%.
In patients with PN, CR can be effort dependent with few or no crackles heard during shallow breathing. In patients with IPF and CHF similar or higher CR was identified during shallow breathing than during deeper than normal breathing. In all three conditions CR did not change significantly following cough or a vital capacity maneuver.
Automated lung sound analysis may provide some help in distinguishing these common and often diagnostically perplexing conditions.
Raymond Murphy, Shareholder Dr. Raymond Murphy is founder and CEO of Stethographics, Inc.; No Product/Research Disclosure Information