Bito Yasuyuki, Soeta Yoshiharu, Nakagawa Seiji, Shibata Toshihiko, Suehiro Shigefumi
Department of Cardiovascular Surgery, Osaka City University, Graduate School of Medicine, 1-4-3, Asahimachi, Abeno-ku, Osaka 545-8585, Japan.
Osaka City Med J. 2005 Dec;51(2):73-81.
Valve sounds are thought to be useful in evaluating the functioning of prosthetic heart valves. In previous reports, two recording instruments have mainly been used, a condenser microphone (instrument A) and an accelerometer (instrument B), respectively. This study aimed to investigate the applicability of these conventional devices in recording mechanical heart valve sounds in daily clinical situations. In addition, two other instruments, namely, a stethoscope including a small microphone in its tube (instrument C) and an electrostethoscope (instrument D), were proposed and examined.
Mechanical valve sounds were recorded from postoperative patients using each-device and the signal to noise ratio (SNR) of each was calculated. Frequency characteristics of the two newly proposed instruments were also investigated by recording a sweep signal in an anechoic chamber.
The SNR values of the new instruments were significantly superior to those of conventional ones (A, sound signals were not defined from noises; B, 0.97 +/- 0.59 dB; C, 11.5 +/- 4.7 dB; and D, 9.4 +/- 3.5 dB, respectively p<0.05). The frequency characteristics of the two newly proposed instruments were also shown to be acceptable (under 10 kHz), though resonance frequency peaks were observed.
Two newly proposed instruments can record mechanical heart valve sounds more noiselessly and with more ease than previous ones, and their frequency characteristics are acceptable.
瓣膜声音被认为有助于评估人工心脏瓣膜的功能。在以往的报告中，主要使用了两种记录仪器，分别是电容式麦克风（仪器A）和加速度计（仪器B）。本研究旨在探讨这些传统设备在日常临床情况下记录机械心脏瓣膜声音的适用性。此外，还提出并测试了另外两种仪器，即管内带有小型麦克风的听诊器（仪器C）和电子听诊器（仪器D）。
使用每种设备记录术后患者的机械瓣膜声音，并计算每种设备的信噪比（SNR）。还通过在消声室中记录扫频信号来研究两种新提出仪器的频率特性。
新仪器的SNR值明显优于传统仪器（A，无法从噪声中分辨出声音信号；B，0.97±0.59 dB；C，11.5±4.7 dB；D，9.4±3.5 dB，p均<0.05）。虽然观察到共振频率峰值，但两种新提出仪器的频率特性也显示是可接受的（低于10 kHz）。
两种新提出的仪器能够比以往仪器更轻松、更安静地记录机械心脏瓣膜声音，并且它们的频率特性是可接受的。
