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1 Division of Internal Medicine, Nishida Hospital, Oita, Japan
2 Division of Respiratory Disease, Oita University Hospital, Oita, Japan Conflicts of interest: none reported
CORRESPONDING AUTHOR: Hajime Kataoka, MD, 3-3-24 Ohte-machi, Saiki-city, Oita 876-0831, Japan, hkata{at}cream.plala.or.jp
| ABSTRACT |
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METHODS After exclusion of comorbid pulmonary and other critical diseases, 274 participants, in whom the heart was structurally (based on Doppler echocardiography) and functionally (B-type natriuretic peptide <80 pg/mL) normal and the lung (X-ray evaluation) was normal, were eligible for the analysis.
RESULTS There was a significant difference in the prevalence of crackles among patients in the low (45–64 years; n = 97; 11%; 95% CI, 5%–18%), medium (65–79 years; n = 121; 34%; 95% CI, 27%–40%), and high (80–95 years; n = 56; 70%; 95% CI, 58%–82%) age-groups (P <.001). The risk for audible crackles increased approximately threefold every 10 years after 45 years of age. During a mean follow-up of 11 ± 2.3 months (n = 255), the short-term (
3 months) reproducibility of crackles was 87%. The occurrence of cardiopulmonary disease during follow-up included cardiovascular disease in 5 patients and pulmonary disease in 6.
CONCLUSIONS Recognition of age-related pulmonary crackles (rales) is important because such clinically unimportant crackles are so common among elderly patients that, without knowledge of this phenomenon, their existence might interfere with the physicians management of cardiopulmonary patients.
Key Words: Physical examination auscultation crackles respiratory sounds rales aging heart failure
| INTRODUCTION |
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| METHODS |
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All screened patients had a physical examination, blood chemistry tests, a 12-lead electrocardiogram (ECG), and a simple chest radiograph. At this second step, patients were excluded if they had high serum creatinine levels (
1.2 mg/dL), abnormal ECG rhythm (atrial fibrillation or left bundle branch block), or radiographic abnormalities. Finally, all the patients screened at the second step underwent a cardiac Doppler echocardiogram and blood sampling for analysis of serum B-type natriuretic peptide (BNP) levels. At this final step, patients were excluded if they had abnormal findings on a Doppler echocardiogram7,8 or high BNP levels (
80 pg/mL).9,10
Because the sensitivity of a simple chest radiograph alone might be insufficient for assessing the structural normalcy of lung tissue, some study patients underwent thoracic high-resolution computed tomography (CT).11–13
We observed a substantial number of participants from 6 to 12 months. During this follow-up period, the short-term (3 or fewer months) reproducibility of the presence or absence of pulmonary crackles and the occurrence of critical cardiovascular or pulmonary disease were evaluated. The protocol was approved by the ethics committee of Nishida Hospital, and all patients provided informed consent.
Evaluation by Auscultation
A single senior cardiologist (H.K.) auscultated carefully the anterior to posterior basilar sites in each hemithorax in seated patients who were asked to perform periodic slow deep respiration. The cardiologist who performed the auscultation was blinded to chest radiograph, Doppler echocardiogram, and high-resolution CT findings. Pulmonary crackles were defined as discontinuous, interrupted explosive sounds during inspiration.14 Audible crackles were classified as fine or coarse crackles according to their dominant acoustic nature.14 Some previous studies reported that basilar crackles are often heard during the first few deep breaths, even in apparently normal persons.4,15 In our study, only inspiratory crackles that appeared recurrently during consecutive respiratory cycles were accepted as the presence of crackles. We graded such basal crackles from 0 to 4 based on the longitudinal extension from the lung base upward to the apex16: a score of 1 indicates crackles over one-quarter of the lung height and a score of 4 indicate crackles over the entire lung height. Additionally, we defined bilateral transverse extension of crackles over two-thirds of the hemithorax as diffuse crackles.
Other Main Measurements
We obtained high-resolution thoracic CT scans12,13 with 1-mm collimation, 130 kVp and 200 mA, by using a high-frequency reconstruction algorithm (X-Vision/GX, Toshiba Co, Ltd, Tokyo, Japan). A single senior pneumologist (O.M.) who was blinded to other clinical tests evaluated the CT image. Serum BNP was measured using the Shionoria assay method.17 The Doppler echocardiogram was performed using a commercially available real-time, wide-angle phased-array system (Aloka SSD-2000, Aloka Co, Ltd, Tokyo, Japan).
Statistical Analysis
Continuous variables are expressed as mean values plus or minus standard deviations, and categorical data are expressed as frequencies and percentages. We assessed differences among the 3 study groups stratified arbitrarily by age by using 1-way analysis of variance for continuous variables with Bonferronis correction for multiple comparisons; they were analyzed using the Kruskal Wallis H test for categorical data and the Mann-Whitney U test with Bonferronis correction for multiple comparisons as the post hoc test. We used a 2-tailed unpaired Students t test and a
2 test for comparisons between patients with and without pulmonary crackles. Using logistic regression analysis, we determined the presence or absence of pulmonary crackles by taking univariate predictors of the appearance of crackles and using iterative modeling procedures to arrive at the most efficient model. The threshold for entry of variables into the model was P <.10. We calculated odds ratios (OR) and 95% confidence intervals (CI), and a 2-tailed P value of <.05 was considered significant. Statistical analyses were performed using SAS Statistical Software, version 8.2 (SAS Institute, Inc, Cary, North Carolina).
| RESULTS |
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12 mm) in 10, left ventricular dilatation (
140 mL) in 14, abnormal peak early-to-atrial velocity (EA) ratio of Doppler-derived left ventricular diastolic dysfunction in 13, and major valvular regurgitation in 27 (2 or more abnormalities in 18 patients). After this final exclusion process, 274 asymptomatic adult patients with sinus rhythm in whom the heart was assumed to be structurally normal (determined by Doppler echocardiography) and functionally normal (determined by serum BNP), and with structurally normal lungs as evaluated by a simple radiograph, remained eligible for analysis.
Clinical Characteristics
Table 1
displays the baseline clinical characteristics of the study participants and the 3 categories stratified by age-groups (low = 45–64 years; n = 97, medium = 65–79 years; n = 121; and high = 80–95 years; n = 56). Men made up 28% of the participants. There were significant differences in demographic features across the 3 age-groups. The higher the age-group, the more likely patients were to have venous insufficiency or edema in the lower leg and higher mean values of serum BNP and creatinine. The prevalence of a smoking habit was not different across the 3 age-groups.
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Among 19 patients without crackles, focal sub-pleural interstitial changes on a CT scan were found in 3 patients (16%), focal septal thickening in 1 (5%), and small nodules in 1 (5%). Of the 74 study patients examined by CT, none showed heart failure-related CT findings,11 such as pulmonary edema, pleural effusion, and venous engorgement.
Predictors of Pulmonary Crackles
Table 3
displays the comparison of the clinical variables between study patients with (n = 92) and without (n = 182) pulmonary crackles. A logistic regression analysis was performed for presence or absence of pulmonary crackles, with age, leg venous insufficiency, leg edema, serum creatinine, and serum BNP as independent variables. Age was the only independent predictor of the presence or absence of pulmonary crackles (Table 4
). For the appearance of crackles, the adjusted OR of age per 10 years was 3.23 (95% CI, 2.22–4.70; P <.001). Other variables were not significant predictors of the presence or absence of pulmonary crackles. Leg edema was strongly associated with the presence of peripheral venous insufficiency in the study population (
2 = 27.2, P <.001).
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| DISCUSSION |
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The prevalence and pathologic significance of crackles in apparently normal persons is subject to controversy.3–5 Although some investigators report that crackles do not occur in normal persons, others disagree. The observations in this study are somewhat consistent with the findings of Cabot et al,3 who reported frequent detection of "crepitant rales" in middle-aged or elderly patients with "normal chests" examined during the first few breaths after shallow tidal breathing. Our findings show that the risk ratio of pulmonary crackles increases approximately threefold every 10 years after 45 years of age in patients with cardiovascular disease and apparently normal heart function. Minimal interstitial changes in some patients with crackles were found with high-resolution CT examination.12,13 Many of our older patients had likely been exposed to various environmental agents over the years, including probable infectious lung disease, which might contribute to the interstitial changes seen on CT or subsequent production of crackles. Such CT findings in the lung with age could be due to environmental pollutants rather than simply aging alone.
In patients with cardiovascular disease, physical examination is the primary step in evaluating the presence and severity of fluid retention in those with possible heart failure.2,6 The appearance of pulmonary crackles is among the most important signs of congestive heart failure. The accuracy of detecting crackles for diagnosing the deterioration of heart failure, however, varies greatly across studies: sensitivity 13% to 70%, specificity 35% to 100%, positive predictive value 19% to 100%, negative predictive value 17% to 85%.18 This variable accuracy among studies might be explained by at least 2 factors, ie, the population studied and the definition of crackles.19
First, the utility of a test is always determined by the nature of the population studied and can only be generalized if it is representative of other populations likely to be of interest. Thus, although pulmonary crackles ought to be a very specific sign, sometimes they are not, perhaps because crackles related to heart failure are so easily confused with those of interstitial fibrosis, pneumonia, and bronchitis.4,14 Recognition of age-related crackles is important because such crackles are so common among apparently normal elderly patients with cardiovascular disease that their existence in the population of interest would additionally aggravate the specificity for diagnosing heart failure status.
Second, the criteria required for determining the crackles related to heart failure also affect the accuracy of the test results for heart failure diagnosis. Many previous studies, except several,16,20,21 lacked definite criteria for diagnosing the presence of crackles related to heart failure, and the mere presence or absence of the crackles was often expressed as the definition. The nature of the age-related crackles in our study, ie, restriction to the lower quadrant of the lung field, would partly support the notion of Stevenson et al16 that physical evidence of pulmonary congestion might be specific for grade 2 or 4 crackles, not for grade 1, but such strict criteria resulted in low sensitivity for diagnosing congestive heart failure.
The physical signs of heart failure in the elderly are often difficult to interpret.22–24 Superimposition of changes caused by aging or other diseases, such as frequent leg edema in association with peripheral venous insufficiency in the elderly, might obscure the typical signs observed in younger patients. Age-related crackles in elderly patients with cardiovascular disease might be mistakenly diagnosed as a sign of heart failure deterioration, and a danger exists when diuretic therapy is inappropriately instituted.4,14 Elderly patients with chronic heart failure and previous decompensation often have persistent pulmonary crackles, even during stable periods,22 associated in some cases with the age-related phenomena, not heart failure status. Whether crackles are related to cardiac dysfunction should be interpreted in light of other clinical tests including, for example, Doppler echocardiography,7,8 serum BNP measurement,17,22,25 or thoracic CT scans.12,13
This study had several limitations. First, more commonly accepted theories26,27 for the production of crackles are associated with airway and air-space opening. The pathogenesis of crackles remains unexplained because the CT examination, undertaken in this study to exclude pathologic lung diseases, might not be suitable for exploring the genesis of crackles. Second, our study defined patients with cardiovascular disease as "functionally normal" based on their plasma BNP levels, but this diagnostic test might not be perfect. Because age, sex, and renal function affect serum BNP levels,25,28 BNP level cannot be used to strictly define functional cardiac status. In this study, we adopted a cutoff level of BNP at less than 80 pg/mL for functionally normal hearts because a BNP level of 80 to 100 pg/mL is widely accepted as a cutoff level for ruling out heart failure status regardless of age.9,10 Importantly, logistic regression analysis did not identify BNP levels as the independent predictor of the appearance of crackles in the this study population. Third, left ventricular diastolic function was not examined precisely, and only one index of Doppler-derived E/A ratio6 was adopted for identifying diastolic dysfunction in the this study. Thus, some of the participants might belong in the category of stage B cardiovascular status, corresponding to a criterion of diastolic dysfunction with preserved systolic function.6 Fourth, this study recruited the study population from highly selected group of patients, which might somewhat limit its generalizability. Finally, despite the importance of crackles for diagnosing acute heart failure decompensation,2,6 there is often considerable disagreement among physicians about the actual presence of crackles in individual patients.20 In our population (n = 65), there was 83% agreement on interpretation of the presence or absence of crackles.
Implications for Clinicians
The recognition of age-related crackles is important because such clinically unimportant crackles are so common among elderly patients that, without knowledge of this phenomenon, their existence might interfere with the physicians management of patients with suspected heart failure or presumable pulmonary disease.
| FOOTNOTES |
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Received for publication September 27, 2007. Revision received December 21, 2007. Accepted for publication December 24, 2007.
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