肺気腫患者の肺胞呼吸音についての検討

Abstract

The author studied the intensity and frequency content of breath sounds in sixteen patients with pulmonary emphysema as compared with those in normal controls. The patients were clinically diagnosed with pulmonary emphysema with moderate to severe obstructive ventilatory impairment (FEV 1/FVC 50.7±10.5%) on pulmonary function test and with low attenuation area suggestive of emphysema on CT. Control subjects were eight non-smoking healthy men with normal pulmonary function test. Recording of breath sounds was done with the subjects in a sitting position for thirty seconds with various flow rates. Flow rate was measured by pneumotachometer via mouth. ECG was recorded simultaneously to eliminate contamination by heart sounds. The signals of breath sounds at six sites on the chest wall were through an amplifier and a band-pass filter (0.1 to 2000 Hz), and digitized to be recorded on a personal computer with signal of flow rate and ECG. Power spectra of the breath sounds for inspiratory blocks of 102. 4 msec when the flow rate was 350ml/sec (low flow rate) or 700ml/sec (high flow rate) were obtained using fast Fourier transform. The segments which were contaminated by heart sounds and various noise were excluded by inspection of sound-spectrogram. Total power was calculated by the sum of power spectra within bandwidth of 100-2000 Hz. Parameters of F25, F50, F75, F95, and H/M power ratio (H : 400～800 Hz, M: 200～400 Hz) were calculated to quantify distribution of frequency spectra of breath sounds. Total power of breath sounds was increased･on upper lung fields at both flow rates and on lower lung fields at low flow rate as compared with those in normal controls. H/M ratio was increased on upper lung fields at both flow rates and on lower lung fields at high flow rate. F95 was increased on both lung fields at high flow rate. In conclusion, at a given flow rate the breath sounds in a patient with emphysema do not decrease in intensity but may increase in frequency. This fact suggests that decreased breath sounds in patients with pulmonary emphysema is due to decreased flow rate.