Modeling sound transmission and reflection in the pulmonary system and chest with application to diagnosis of a collapsed lung

Abstract

Experimental studies have shown that a pneumothorax (collapsed lung) substantially alters the propagation of sound introduced at the mouth of an intubated subject and measured at the chest surface. Thus, it is hypothesized that an inexpensive diagnostic procedure could be developed for detection of a pneumothorax based on a simple acoustic test. In the present study, theoretical models of sound transmission through the pulmonary system and chest region are reviewed in the context of their ability to predict acoustic changes caused by a pneumothorax, as well as other pathologic conditions. Such models could aid in parametric design studies to develop acoustic means of diagnosing pneumothorax and other lung pathologies. Extensions of previously developed simple models of the authors are presented that are in more quantitative agreement with experimental results and that simulate both transmission from the bronchial airways to the chest wall, as well as reflection in the bronchial airways. [Research supported by NIH NCRR Grant No. 14250 and NIH NHLBI Grant No. 61108.]

Early detection of deteriorating ventilation by monitoring bilateral chest wall dynamics in the rabbit

“…Numerous studies have explored the use of auscultation for ventilation monitoring, based on the characterization of breath sound patterns in various diseases [12][13][14]. However, the analysis of breath sounds and comparison with sounds in databanks have inherent limitations because human breath sounds vary among different individuals [14][15][16][17].…”

“…However, the analysis of breath sounds and comparison with sounds in databanks have inherent limitations because human breath sounds vary among different individuals [14][15][16][17]. The method described here detects changes in ventilation dynamics relative to the individual's baseline measurements.…”

Design of a sound source phantom with uniform surface signal

“…A light weight (3 gm, 5 cm diameter, and 0.3 cm high) piezo-electric speaker (VSB50EWH0301B, muRata, Rockmart, GA) was chosen as the sound source to minimize the weight and volume of the phantom. Coupling materials from earlier studies included gelatin [13,7], different elastomers [6,10], water bladders [9], and air columns [11]. While gelatin mechanical properties are documented in many studies [14], investigations of relevant properties of candidate elastomers were not pursued until recently [15].…”

“…The advantage of using a phantom is the ability to generate reproducible acoustic inputs to the sensor being tested [5]. Basic phantom designs included sound sources buried in viscoelastic materials [6,7], water-filled polymer or latex bladders [8,9], electromagnetic speakers covered with viscoelastic layers [10], and a sound source coupled to the sensor with an air chamber [11]. While many earlier studies were successful in providing estimates of relative response of some sensors [3,5,6,10], the acoustic characteristics of most phantoms remain essentially undocumented.…”

Acoustic source separation for the detection of coronary artery sounds

“…Many of these studies have considered idealized geometries. 28,29 Others have considered more general models but have focused their attention on respiratory rather than cardiovascular sounds. 30,31 Our finite element model builds on much of this previous work, particularly for material properties.…”