This previously unrecognized behavior of lung sounds over short distances might reflect spatial variations of airways and diaphragms during breathing. During inspiration, increasing delay and amplitude of sound at the caudal relative to the cranial sensor were also observed during passive transmission in several subjects. Lung sound intensity has been studied in patients with asthma 20, 21, 31, 39, 40 and COPD 20, 28, 41, 42 in stable states and after allergen inhalation (i.e., Dermatophagoides pteronyssinus SQ502, methacholine, and histamine). Volume-dependent variations in phase (< or =1.5 ms) and amplitude (< or =11 dB) were observed at the lower lobes in the 150- to 300-Hz band. 1.2.2.2 In the Presence of a Respiratory Condition. Automated mapping of lung sound distribution is a novel area of interest currently investigated in mechanically ventilated, critically ill patients. The data showed that lung sound amplitude (mean or peak) was linearly related to V in all subjects (r for mean AMP vs Vmax:0.77, 0.85, 0.69, 0.89 r for peak. Cross correlation established the phase relation of sound between sensors. The same sounds were also submitted to an automated V-correction procedure to evaluate its adequacy in automatically adjusting for the effect of variations in Vmax on lung sound amplitude. The varying amplitude of adventitious sounds. Average sound amplitudes were obtained after band-pass filtering to 75-150, 150-300, and 300-600 Hz. The intensity of respiratory sounds can mask the adventitious sounds, resulting in only normal sounds being heard. Lung sounds were recorded at the posterior right upper, right lower, and left lower lobes during targeted breathing (1.2 +/- 0.2 l/s volume = 20-50 and 50-80% of vital capacity) and passive sound transmission (< or =0.2 l/s volumes as above). Single-sided amplitude spectrum is plotted to observe the presence of noise portions being suppressed. We investigated volume-dependent variations of lung sound phase and amplitude between two closely spaced sensors in five adults. 3 (a) & (b) reflects the single-sided amplitude spectrum of the original noisy COPD lung sound signal obtained before denoising and the single-sided amplitude spectrum of the COPD lung sound signal obtained after denoising, respectively. Acoustic imaging of the respiratory system demonstrates regional changes of lung sounds that correspond to pulmonary ventilation.
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