Respiratory sound energy and its distribution patterns following clinical improvement of congestive heart failure: a pilot study

Abstract

Background: Although congestive heart failure (CHF) patients typically present with abnormal auscultatory findings on lung examination, respiratory sounds are not normally subjected to additional analysis. The aim of this pilot study was to examine respiratory sound patterns of CHF patients using acoustic-based imaging technology. Lung vibration energy was examined during acute exacerbation and after clinical improvement.

Methods: Respiratory sounds throughout the respiratory cycle were captured using an acoustic-based imaging technique. Twenty-three consecutive CHF patients were imaged at the time of presentation to the emergency department and after clinical improvement. Digital images were created (a larger image represents more homogeneously distributed vibration energy of respiratory sound). Geographical area of the images and respiratory sound patterns were quantitatively analyzed. Data from the CHF patients were also compared to healthy volunteers.

Results: The median (interquartile range) geographical areas of the vibration energy image of acute CHF patients without and with radiographically evident pulmonary edema were 66.9 (9.0) and 64.1(9.0) kilo-pixels, respectively (p < 0.05). After clinical improvement, the geographical area of the vibration energy image of CHF patients without and with radiographically evident pulmonary edema were increased by 18 +/- 15% (p < 0.05) and 25 +/- 16% (p < 0.05), respectively.

Conclusions: With clinical improvement of acute CHF exacerbations, there was more homogenous distribution of lung vibration energy, as demonstrated by the increased geographical area of the vibration energy image.

Figure 1

Vibration energy image. 36 vibration response imaging (VRI) sensors are spaced over the patient's back and detect vibrations during respiration. The size of the dots is a cartoon representation of the amount of vibration energy detected by that sensor. When the detected vibrations are uniform, the resulting VRI image will be large (A). When the detected vibration is less homogeneous, i.e. if the lower sensors have decreased vibrations (B) or if the middle sensors detect increased vibration (C), a smaller VRI image results. The visual geographical area is therefore determined not by intensity of vibration but by the distribution of intensity. VRI: vibration response imaging.

Figure 2

Representative vibration response imaging images and chest radiographs. A, Healthy volunteer. B, congestive heart failure (CHF) patients without radiographically evident pulmonary edema (REPE). C, CHF patients with REPE. D, Mechanically ventilated CHF patients with REPE. VRI, vibration response imaging. CHF, congestive heart failure. REPE, radiographically evident pulmonary edema.

Figure 3

Geographical area of vibration images during maximal inspiration in healthy volunteers, acute CHF exacerbation patients without and with REPE and CHF patients with REPE mechanically ventilated. CHF, congestive heart failure. REPE, radiographically evident pulmonary edema. Boxes show median and interquartile ranges and I bars represent highest and lowest values.* = lower area values compared to healthy volunteers (P < 0.05).

Figure 4

Geographical area of vibration images during maximal inspiration in acute CHF exacerbation patients without and with REPE on admission (Before) increased after clinical improvement (After) (*, P < 0.05). Each color/line represents a patient. CHF, congestive heart failure. REPE, radiographically evident pulmonary edema.

Figure 5

Vibration energy during maximal inspiration in healthy volunteers, acute CHF exacerbation patients without and with REPE and CHF patients with REPE mechanically ventilated. CHF, congestive heart failure. REPE, radiographically evident pulmonary edema.* = higher vibrational energy when compared to normal controls (P < 0.05).

Figure 6

Vibration energy during maximal inspiration in acute CHF exacerbation patients without and with REPE on admission (Before) decreased after clinical improvement (After) (* = P < 0.05). Each color/line represents a patient. CHF, congestive heart failure. REPE, radiographically evident pulmonary edema.

Figure 7

In mechanically ventilated CHF patients with radiographically evident pulmonary edema, geographical area (A) of vibration energy images increases and vibration energy (B) during maximal inspiration decreases after clinical improvement (* = P < 0.05). Each color/line represents a patient. CHF, congestive heart failure. REPE, radiographically evident pulmonary edema.