Crackles in Patients with Fibrosing Alveolitis, Bronchiectasis, COPD, and Heart Failure

doi:10.1378/chest.99.5.1076

Chest

Volume 99, Issue 5, May 1991, Pages 1076-1083

https://doi.org/10.1378/chest.99.5.1076 Get rights and content

We have studied the crackling lung sounds of ten patients with cryptogenic fibrosing alveolitis, ten with bronchiectasis, ten with chronic obstructive pulmonary disease, and ten with heart failure by analyzing frequency, waveform, and timing of crackles. The upper frequency limit of inspiratory sounds was higher in CFA than in COPD or in HF. The period of crackling was shorter in COPD than in CFA or BE. Inspiratory crackling terminated significantly earlier in COPD than in CFA, BE, or HF. The initial deflection width and the two-cycle duration of the expanded waveforms of crackles were smaller in CFA than in BE, COPD, or HF. The largest deflection width was smaller in CFA than in BE, HF, or COPD and smaller in BE than in HF. The results indicate that crackling lung sounds in different diseases have distinctive features and that their analysis can be of diagnostic value. (Chest 1991; 99:1076-83)

Section snippets

PATIENTS

We have studied 40 patients, of which 29 were men, with 4 different diseases with crackling lung sounds detected by ordinary lung auscultation: CFA (n = 10), BE (n = 10), COPD (n = 10), and HF (n = 10), in each. Their mean age (mean ± SD) was 56 ± 8 years. The lung function studies and anthropometric data on the patients, grouped according to the diagnoses, are presented in Table 1. The Spirometric values were examined on the day of the sound recordings.

The diagnosis of the patients with CFA

METHODS

The lung sound recordings were performed in an acoustically isolated chamber with the patient in the sitting position. The patients were asked to breathe deep, slow inspirations and expirations with a peak flow of about 1 L/s. Air flow from the mouth was recorded with a pneumotachograph with the nose closed. The sounds were recorded with two microphones (with a response range from 4 Hz to 20 kHz), one for each lung. The microphones were encased in plastic supports forming a standard air space

RESULTS

The results of sound spectral analysis and phonopneumographic measurements from inspiratory breathing cycles are presented in Table 2. The frequency of maximum intensity in inspiration was the highest in patients with CFA (210 ± 90 Hz), but there were no significant differences among the patient groups. The upper frequency limit at the intensity level of −20 dB was significantly higher in patients with CFA (550 ± 110 Hz) than in patients with COPD (p<0.005) or HF (p<0.001). The peak flow of

DISCUSSION

The aim of this study was to investigate the waveform and timing of crackling sounds in four common diseases with different pulmonary pathophysiologic findings. Therefore, patients with clearly audible crackles by ordinary auscultation were selected. We did not intend to study the prevalence of crackles among the patients with the four diagnoses studied. In the patient selection, other simultaneous pulmonary diseases were excluded, and internationally accepted diagnostic criteria were followed.

ACKNOWLEDGMENTS

The authors are grateful to Kari Kallio, B.Sc.(Eng.), Pekka Karp, Dr.Sc.(Eng.), Mika Raivio, B.Sc.(Eng.), Tony Rosqvist, M.Sc.(Eng.) and Hannu Seitsonen M.Sc.(Eng.), for their collaboration and useful discussions. The help of Ossi Korhola, M.D., in evaluating the x-ray findings and of Professor Seppo Sama and Ritva Luukkonen, Dr. Sc., for guidance in statistical problems is appreciated.

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Crackle is a lung sound widely employed by health staff to identify respiratory diseases. The two-cycle duration (2CD) is a quantitative index pointed out by the American Thoracic Society and the European Respiratory Society to classify respiratory crackles as fine or coarse. However, this index, measured in the time domain, is highly affected by noise and filters of recording systems. Such factors hamper the analysis of data reported by different research groups. This work proposes a new index based on the instantaneous frequency of crackles estimated by means of discrete-time pseudo Wigner-Ville distribution.
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La durée d’un craquement pulmonaire (< 20 ms) ne permet pas sa reconnaissance psychoacoustique par le clinicien en termes de durée et de contenu fréquentiel. Les auteurs posent l’hypothèse que l’information psychoacoustique est contenue dans le bruit respiratoire environnant en distinguant le phénomène excitateur du rôle du résonateur.
Huit patients atteints de BPCO, de pneumonie virale, de bronchiectasies, de décompensation cardiaque, d’hypoprotéinémie et de fibrose pulmonaire ont été recrutés pour cette étude. Trente-six craquements inspiratoires, leurs composants et les bruits respiratoires ont été analysés dans les domaines temporel et fréquentiel, soit 12 craquements de basse fréquence (BPCO, n = 4), moyenne fréquence (bronchiectasies, n = 1) et haute fréquence (pneumonie, n = 1, décompensation cardiaque n = 1, hypoproténémie n = 1, fibrose pulmonaire n = 1).
Les résultats temporels et fréquentiels ne montraient pas de différences significatives au sein de chaque catégorie mais des différences significatives entre les fréquences de pic des trois catégories de craquements et du bruit respiratoire.
Le bruit respiratoire associé à la densité du tissu pulmonaire est le résonateur qui détermine le contenu fréquentiel du craquement perçu par le clinicien.
The overall duration of a pulmonary crackle is usually less than 20–30 ms but psychoacoustics demonstrates that an acoustical event with a duration of less than 20–40 ms cannot be estimated in terms of pitch and duration. We pose the hypothesis that the main resonant information is contained into the breath sounds following the crackle.
Eight patients with COPD, viral pneumonia, bronchiectasis, congestive heart failure, hypoproteinemia and fibrosing alveolitis were recruited for this study. Thirty-six crackles were analyzed in time and frequency domains; 12 in each category of low, medium and high frequencies. The acoustic features of the crackles, their segments (initial deflection width, first cycle duration, two cycles duration, decay segment) and the breath sounds following the crackles were compared.
The study confirms the differences between the three crackles categories in time and frequency domains. No statistical differences were found between the decay segments and breath sounds in each category.
Breath sounds modified by lung tissue density could be the main resonators determining the fundamental transmission frequencies of crackle signals. Combined acoustic analysis of crackles and breath sounds could replace single analysis of isolated crackles.
History and Physical Examination
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Identification of Velcro rales based on Hilbert-Huang transform
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Velcro rales, as a kind of crackles, are relatively specific for lung fibrosis and usually the first clinical clue of interstitial lung disease (ILD). We proposed an automatic analytic tool based on Hilbert–Huang transform (HHT) for the computerized identification of Velcro rales. In particular, HHT was utilized to extract the energy weight in various frequency bands ( ${EW}_{FB}$ ) of crackles and to calculate the portion of crackles during late inspiration. Support vector machine (SVM) based on the HHT-derived measures was used to differentiate Velcro rales from other crackles. We found that there were significant differences in the extracted parameters between Velcro rales and other crackles, including ${EW}_{75 - 200}$ , ${EW}_{500 - 1000}$ and the proportion of crackles that appeared during the late inspiration. The discrimination results obtained from SVM achieved a concordance rate up to $92.20 % \pm 1.80 %$ as confirmed by the diagnosis from experienced physicians. For practical purpose, the proposed approach may have potential applications to improve the sensitivity and accuracy of auscultation and conduct automatic ILD diagnose system.
Characterization of crackles from patients with fibrosis, heart failure and pneumonia
2013, Medical Engineering and Physics
Citation Excerpt :
Processing the crackles with a 150 Hz HPFCF and analyzing them with DPWD and MGM (Table 4), it was found that the maximum frequency of fibrosis crackles was superior to the ones found in heart failure and pneumonia. However, the maximum frequency estimated in this work was almost twice that obtained by Piirilä et al. [12,13]. The heart failure crackles were also found to have the lowest maximum frequency.
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This study was supported by grants from the Finnish Association

Against Tuberculosis and the Paulo Foundation.

Manuscript received August 2; revision accepted November 12.

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