Thursday, May 15, 2008

When is a crackle a rale? (or vice versa)

One of our medical students came to the History of Medicine Room today, having been challenged by her preceptor to find out when "rales" started being called "crackles." Of course, tracing any shift in terminology requires old dictionaries, and luckily we have a few here close to hand. A quick glance at Gould's 1896 Illustrated dictionary of medicine, biology, and allied sciences shows that, rather than being a synonym for rale, crackle is actually a more precise term, being the sound "heard over a lung in which softening of the tuberculosis deposits has begun to take place."

Gould actually devotes slightly more than one full page to a chart of the various types of rales, from amphoric to sub-crepitant, 23 in all. Four of those are types of crackles, including small, medium, large, and dry crackling, all found in tubercular patients (the dry crackling also manifesting itself in patients with pulmonary gangrene).

What does this tell us about the state of the physical examination today? The 29th edition of Dorland's (the most modern dictionary in the office here) and the NLM list of Medical Subject Headings both equate crackles with rales, and apparently some clinicians think the former term has simply replaced the latter in common usage.

This semantic blurring of the varieties of respiratory sounds is a symptom of the degradation of the physical examination in modern medical practice, where chest x-rays and blood tests have become substitutes for auscultation and percussion, elevating the "science" of technology over the "art" of human experience--and costing us all a lot more in lab fees as a consequence.

But I'm pretty sure we're better off, in general. There were, undoubtedly, some legendary diagnosticians here at OHSU--and at other institutions, I imagine--who could not only distinguish a moist rale from an amphoric rale, but could tell you the precise functional residual capacity of the patient's lungs while they were at it. But what about the average doc, who was maybe a little hard of hearing, or suffering from a head cold? As much as we all might appreciate the art of the physical exam, there really is something to be said for calibrated measurement devices.

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