Crackle Pitch and Rate Do Not Vary Significantly During a Single Automated-Auscultation Session in Patients With Pneumonia, Congestive Heart Failure, or Interstitial Pulmonary Fibrosis
OBJECTIVE: To determine the variability of crackle pitch and crackle rate during a single automated-auscultation session with a computerized 16-channel lung-sound analyzer. METHODS: Forty-nine patients with pneumonia, 52 with congestive heart failure (CHF), and 18 with interstitial
pulmonary fibrosis (IPF) performed breathing maneuvers in the following sequence: normal breathing, deep breathing, cough several times; deep breathing, vital-capacity maneuver, and deep breathing. From the auscultation recordings we measured the crackle pitch and crackle rate. RESULTS: Crackle
pitch variability, expressed as a percentage of the average crackle pitch, was small in all patients and in all maneuvers: pneumonia 11%, CHF 11%, pulmonary fibrosis 7%. Crackle rate variability was also small: pneumonia 31%, CHF 32%, IPF 24%. Compared to the first deep-breathing maneuver
(100%), the average crackle pitch did not significantly change following coughing (pneumonia 100%, CHF 103%, IPF 100%), the vital-capacity maneuver (pneumonia 100%, CHF 92%, IPF 104%), or during quiet breathing (pneumonia 97%, CHF 100%, IPF 104%). Similarly, the average crackle rate did not
change significantly following coughing (pneumonia 105%, CHF 110%, IPF 90%) or the vital-capacity maneuver (pneumonia 102%, CHF 101%, IPF 99%). However, during normal breathing the crackle rate was significantly lower in the patients with pneumonia (74%, P < .001) and significantly
higher in the patients with IPF (147%, P < .05) than it was during deep breathing. In patients with CHF the average crackle rate during normal breathing was not significantly different from that during the first deep-breathing maneuver (108%). CONCLUSIONS: Crackle pitch and rate
were surprisingly stable in all 3 conditions. Neither crackle pitch nor crackle rate changed significantly from breath to breath or from one deep-breathing maneuver to another, even when the maneuvers were separated by cough or the vital-capacity maneuver. The observation that crackle rate
is a reproducible measurement during one automated-auscultation session suggests that crackle rate can be used to follow the course of cardiopulmonary illnesses such as pneumonia, IPF, and CHF.
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