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Asthma lung sounds8/3/2023 At the very severe end of airway obstruction, if there is very little to no airflow, then no wheeze will be heard despite severe airway obstruction. And so, the amplitude of auscultated wheeze has no bearing on the severity of airway obstruction. It was determined that the pitch of a wheeze is a reflection of the stiffness, thickness, and longitudinal tension of the airway's wall. Subsequent clinical studies have shown that the pitch and, more so, duration of wheeze are the only two characteristics that correlate well with the severity of airway obstruction. The degree of bronchial obstruction is also proportional to the number of airways that are producing wheeze. A physiologic trial done in the 1980s identified the determinants of the pitch of a sound generated within collapsible tubes. The characteristics of their sound include how loud they are (i.e., the amplitude), how long they last and how intense (i.e., high pitched) they sound. Wheezes are thought to be the product of fluttering vibrations of narrowed airway walls, induced by a diminished airflow velocity. The presence of wheezing does not always mean that the patient has asthma, and a proper history and physical exam are required to make the diagnosis. Modern-day computerized waveform analysis has allowed us to characterize wheeze with more precision and given us its definition as a sinusoidal waveform, typically between 100 Hz and 5000 Hz with a dominant frequency of at least 400 Hz, lasting at least 80 milliseconds. Wheeze may be audible without the aid of a stereoscope when the sound is loud, but in most cases, wheezes are auscultated with a stethoscope. Wheeze is a musical, high-pitched, adventitious sound generated anywhere from the larynx to the distal bronchioles during either expiration or inspiration. Rene Laennec's development of the stethoscope in 1816 has enabled a better appreciation of wheeze at the bedside, in comparison to the previously established practice of ear-to-chest auscultation. Wheezing is the symptomatic manifestation of any disease process that causes airway obstruction.
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