Lung Auscultation

Chapter 14 Lung Auscultation





Generalities


Lung auscultation has long suffered from a complex and onomatopoeic terminology that goes back to the original stethoscope and its inventor. Recent application of computer technology has rekindled this art by facilitating acoustic analysis. Still, its major difficulty lies not in the identification of sounds (which is much easier than for cardiac sounds and murmurs), but in their interpretation. And despite recent attempts at standardization, terminology remains a vexing issue.



1 Who invented lung auscultation?


Auscultation of the direct or immediate variety (that is, without the use of the stethoscope) has actually been around for a long time. References to breath sounds first appeared in the Ebers papyrus (c. 1500 BC), the Hindu Vedas (c. 1400–1200 BC), and the Hippocratic writings (4th century BC). In fact, Hippocrates himself taught and practiced auscultation, advising physicians to apply their ears to the patient’s thorax in order to detect various diagnostic sounds. Since then, chest auscultation was mentioned by Caelius Aeralianus, Leonardo Da Vinci, Ambroise Paré, William Harvey, Giovanni Battista Morgagni, Gerhard Van Swieten, William Hunter, and many others. The hypochondriacal Robert Hooke, an assistant to Robert Boyle and one of the first scientists to use the word cell (1664), even had a good insight in describing heart sounds. He wrote, “Who knows? It may be possible to discover the motions of internal parts. .. by the sound they make.” Yet, during the 18th and early 19th centuries, direct auscultation fell rapidly out of favor, being replaced by a newer diagnostic modality: chest percussion. It took a lot of serendipity (and plenty of shyness) to rekindle it as indirect auscultation, that is, one “mediated” by a newly invented cylindrical instrument, the stethoscope. The hero of this rediscovery was an introverted, diminutive, very asthmatic, very prudish, and very tuberculotic Breton physician, named René Théophile Hyacinthe Laënnec. In the fall of 1816 (a year after the battle of Waterloo), he was summoned to the bedside of a young woman with a chest illness. Because percussion was technically difficult (given the large size of the woman’s breasts) and since direct auscultation (i.e., placing the physician’s naked ear over the patient’s naked chest) was, in Laënnec’s own words, “inadmissible” (given the young lady’s age and gender), Laënnec came up with a totally different approach. He remembered that a few days before, while walking in the Tuileries garden in Paris, he had seen children scraping a stick of wood and listening to the other end. Imagining that something similar could be tried with patients’ chests, he fetched a cardboard, rolled it into a cylinder, applied it to the lady’s thorax, and to his amazement, was able to hear very distinct lung sounds. And all of this without even touching her! Being handy (he used to make flutes), Laënnec quickly manufactured a wooden contraption, shaped like a flute, which he started taking regularly on rounds. He dubbed it the cylinder (and this, in turn, gave his students a chance to dub him “the cylindromaniac”). Yet, in academic circles the tool came to be known as the stethoscope, from the Greek term for “inspector of the chest.” Whatever its name, the gadget allowed Laënnec to gather over 3 years an astounding wealth of clinical–pathological correlations, which he then published on August 15, 1819—in a two-volume book titled De l’Auscultation Mediate. There he reported masterly descriptions of several chest diseases, many previously unheard (no pun intended), like bronchitis, bronchiectasis, pleurisy, lobar pneumonia, hydrothorax, emphysema, pneumothorax, pulmonary edema, pulmonary gangrene and infarction, mitral stenosis, esophagitis, peritonitis, cirrhosis (hence the eponym Laënnec’s cirrhosis), and, of course, tuberculosis. And since autopsy was the ultimate benchmark for all these conditions, several ended up acquiring a pathological name. The book also presented an entirely new terminology, rooted in daily life examples and enriched by Laënnec’s fascination with Greek and Latin language. Among such neologisms were stethoscope, but also auscultation, rales, rhonchus, fremitus, crackled-pot sound, metallic tinkling, egophony, bronchophony, cavernous breathing, puerile breathing, veiled puff, and bruit. The first edition of De l’Auscultation sold for 13 francs (16 if purchased with a wooden stethoscope) and sold quite badly. But when the considerably rewritten second edition hit the press, stethoscopy had already become the standard of chest examination. By the time of Laënnec’s premature death from tuberculosis (in 1826, at age 45), many physicians were carrying stethoscopes, all personally made by Laënnec. In fact, the posthumous third and fourth editions of 1831 and 1837 sold very well, establishing the tool not only as a symbol of the art of medicine, but also as the centerpiece of bedside assessment. To reach a diagnosis, physicians could now rely on “objective” findings (instead of subjective symptoms reported by patients). They could finally tell their patients what they had wanted to say for a long time, “Shut up and let me listen to your lungs!” A new era had begun: one in which the patient was going to become first a sound, then a laboratory number, and, finally, a flickering computer image.









A. Breath Sounds (Basic Lung Sounds)




































41 What is the best bedside predictor for the presence of chronic obstructive lung disease?


A reduction in breath sound intensity (BSI). A total of 32 findings has been said to indicate COPD, with many arguing strongly for its presence (Table 14-3), yet BSI is the single best index of emphysema. Early inspiratory crackles also argue for obstruction (LR, 14.6), but mostly chronic bronchitis. If progressive over time, BSI reduction can help monitor methacholine challenge, even when wheezing is absent. Finally, any two of the following virtually rule in airflow limitation: >70-pack-years of smoking, decreased breath sounds, or history of COPD. Years of cigarette smoking, subjective wheezing, and either objective wheezing or peak expiratory flow rate also predict the likelihood of airflow limitation in males. Although other signs have been linked to obstruction (objective wheezing, barrel chest, positive match test, rhonchi, hyperresonance, and subxiphoid apical impulse), on multivariate analysis only three remain significantly associated with its diagnosis: self-reported history of COPD (LR, 4.4), wheezing (LR, 2.9), and FET >9 seconds (LR, 4.6). Patients with all three have an LR of 33 (ruling in COPD); those with none have an LR of 0.18 (ruling out COPD).


Table 14-3 Accuracy of Bedside Findings for the Evaluation of Obstructive Lung Disease: Likelihood Ratios, Point Estimates, and 95% Confidence Intervals







































































Findings Positive LR(95% CI) Negative LR(95% CI)
Subxiphoid cardiac impulse 7.4 (2.0, 27.1) 0.9 (0.7, 1.1)
Absent cardiac dullness 11.8 (1.2, 121.4) 0.9 (0.7, 1.1)
Hyperresonance 5.1 (1.7, 15.6) 0.7 (0.5, 1.0)
Diaphragm excursion <2   cm 5.3 (0.8, 35.0) 0.9 (0.7, 1.1)
Breath sound intensity <9 10.2 (4.6, 22.7)
Breath sound intensity 10–12 3.6 (1.4, 9.5)
Breath sound intensity 13–15 0.7 (0.3, 1.5)
Breath sound intensity >15 0.1 (0, 0.3)
Forced expiratory time <3   sec 0.2 (0.1, 0.3)
Forced expiratory time 3–9   sec 1.3 (0.5, 2.9)
Forced expiratory time >9   sec 4.8 (1.3, 17.6)
Early crackles, detecting obstructive disease 14.6 (3.0, 70) 0.4 (0.1, 1.4)
Early crackles, detecting severe obstruction 20.8 (3.0, 142.2) 0.1 (0, 0.4)
Unforced wheezes, detecting obstructivedisease 6.0 (2.4, 15.1) 0.7 (0.6, 1.0)
Methacholine wheezes, detecting asthma 6.0 (1.5, 24.3) 0.6 (0.4, 0.9)
Diminished breath sounds, detecting asthma 4.2 (1.9, 9.5) 0.3 (0.1, 0.6)

(Adapted from McGee S: Evidence-Based Physical Diagnosis. Philadelphia, WB Saunders, 2001.)













Apr 2, 2017 | Posted by in GENERAL SURGERY | Comments Off on Lung Auscultation
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