Production mechanism of crackles in excised normal canine lungs

Abstract

Lung crackles may be produced by the opening of small airways or by the sudden expansion of alveoli. We studied the generation of crackles in excised canine lobes ventilated in an airtight box. Total airflow, transairway pressure (Pta), transpulmonary pressure (Ptp), and crackles were recorded simultaneously. Crackles were produced only during inflation and had high-peak frequencies (738 +/- 194 Hz, mean +/- SD). During inflation, crackles were produced from 111 +/- 83 ms (mean +/- SD) prior to the negative peak of Pta, presumably when small airways began to open. When end-expiratory Ptp was set constant between 15 and 20 cmH2O and end-expiratory Ptp was gradually reduced from 5 cmH2O to -15 or -20 cmH2O in a breath-by-breath manner, crackles were produced in the cycles in which end-expiratory Ptp fell below -1 to 1 cmH2O. This pressure was consistent with previously known airway closing pressures. When end-expiratory Ptp was set constant at -10 cmH2O and end inspiratory Ptp was gradually increased from -5 to 15 or 20 cmH2O, crackles were produced in inspiratory phase in which end-inspiratory Ptp exceeded 4-6 cmH2O. This pressure was consistent with previously known airway opening pressures. These results indicate that crackles in excised normal dog lungs are produced by opening of peripheral airways and are not generated by the sudden inflation of groups of alveoli.

Adaptive Lagrangian–Eulerian computation of propagation and rupture of a liquid plug in a tube

“…This suggested link between plug rupture and crackles is in agreement with findings of Munakata et al [39] which shows, experimentally in canine lungs, that the most probable cause for fine crackles is opening and closing of airways rather than abnormal airway collapsibility. Naturally, more rigorous investigation is needed to establish a direct link with quantitative relationships.…”

Acoustic evidence of airway opening during recruitment in excised dog lungs

“…The distribution of these ⌬V, which correspond to avalanches reaching the alveoli, should follow a power law (32,33). Additionally, because airway opening is also associated with crackle sound generation (2,6,8,23,25,27), we expect that the density of crackles is highest near the lower knee of the P-V curve. To test these predictions, we measured P-V loops in normal isolated dog lung lobes during inflation from the collapsed state to total lobe capacity.…”

“…To test these predictions, we measured P-V loops in normal isolated dog lung lobes during inflation from the collapsed state to total lobe capacity. Recruitment in the form of discrete lung ⌬V was assessed with a high-sensitivity flowmeter, and airway openings were identified as individual crackles from lung sound measurements (23).…”

Fluctuations, Noise and Scaling in the Cardio-Pulmonary System

“…Forgacs was the first to propose that crackles are associated with sudden opening of closed airways [50]. The discrete emission of crackles from the lung tissue has also been modeled as a stress-relaxation quadrupole [51], and this work has received experimental support [52]. Despite the fact that characteristics of individual crackles have long been used as diagnostic tools [53,54], the statistical properties of crackles have only been recently analyzed [55,56].…”