Are Crackles an Appropriate Outcome Measure for Airway Clearance Therapy?

Abstract

BACKGROUND: There is an urgent need to develop new outcome measures for respiratory therapy, to evaluate its effectiveness. Adventitious sounds generated from the lungs (crackles and wheezes), can now be quantified and characterized objectively with computer technology. To our knowledge, this is the first reported study designed to assess any change in lung crackles before and after a single session of airway clearance therapy. METHODS: Twenty-three stable bronchiectasis patients were recruited from United Kingdom out-patient clinics and treated with a single session of airway clearance therapy, using the active cycle of breathing technique. Sound recordings were made before and after the session at 7 anatomical chest locations. Computerized lung sound analysis was used to measure crackle parameters: 2-cycle deflection width (2CD), and crackle number per breath cycle (nBC). Perceived breathlessness, lung function, and oxygen saturation data were also recorded. RESULTS: Crackle mean 2CD and mean nBC increased post intervention. Sixteen participants (70%) showed a statistically significant difference in mean crackle 2CD before and after the session at > 1 chest location. Thirteen (57%) participants had a difference between mean crackle 2CD before and after the intervention > 1 Smallest Real Difference (SRD, mean SRD ‫؍‬ 2.23 ms) at > 1 chest location. Differences in mean crackle nBC before and after the intervention did not exceed the SRD (mean SRD ‫؍‬ 32 crackles per breath cycle) in any participant. Perceived breathlessness was significantly reduced post intervention; no significant changes were observed in either lung function or oxygen saturation. CONCLUSIONS: Crackle duration (2CD) was found to change after a single session of airway clearance therapy, and shows promise as a new outcome measure for respiratory therapy interventions.

Computerized Adventitious Respiratory Sounds as Outcome Measures for Respiratory Therapy: A Systematic Review

“…The majority of the included studies were quasi-experimental, 5,[20][21][22][23][24][25] 3 studies were observational, [26][27][28] and 2 studies were randomized controlled trials (Table 2). 29,30 Ten studies recruited patients receiving specialized care, and 2 studies recruited patients during hospital admission.…”

“…20,22,23,30 The interventions in most studies consisted of pharmacotherapy [20][21][22][23][24][25][26][27][28][29][30] ; only 2 studies combined pharmacotherapy with respiratory physical therapy. 5,29 The respiratory physical therapy consisted mainly of an active cycle of breathing techniques, 5,29 but also breathing retraining techniques (incentive spirometry, thoracic mobility, expansion and flexibility exercises, and aerobic training). 29 In almost all studies, the respiratory sounds were recorded in more than one chest location; however, in 3 studies recordings were performed exclusively in the trachea.…”

“…ARSs provide crucial information on respiratory dysfunction, 4 and changes in their characteristics (eg, intensity, duration, timing) might inform the clinical course of respiratory diseases and treatments. 5,6 Through the use of CORSA, ARSs have been found to be a more sensitive indicator, detecting and characterizing the severity of the respiratory disease before any other measure. 7 Thus, this approach, through objective data collection and management, generation of permanent records of the measurements made with easy retrievability, and graphic representations, assists with the diagnosis and monitoring of respiratory diseases.…”

The Relationship Between Crackle Characteristics and Airway Morphology in COPD

“…6 CALSA is an inexpensive, noninvasive process with potential to be an objective diagnostic and monitoring tool for clinical practice. 6,18 The aim of this study was therefore to explore the relationship between crackles (analyzed using CALSA) and airway geometry and lung parenchyma measurements (quantified by HRCT) to test whether crackles can be used as an indicator of COPD.…”

“…All lung sound files from the 6 areas of chest wall were processed using a customized algorithm written in Matlab, used in previous research. 6,18 Crackle characteristics, ie, crackle 2CD and NCpB, were exported into an Excel (Microsoft, Redmond, Washington) file for analysis.…”