Chin J G, Vermariën H, Koops J, van Vollenhoven E, Voogd P J
Med Prog Technol. 1986;11(1):5-15.
A miniature esophageal microphone has been constructed. It has a cylindrical shape with 5-mm outer diameter and 25-mm length. It is a type of accelerometer that detects vibration from the esophageal wall. It has a resonance frequency of 2.1 kHz and an acceleration charge sensitivity of 2.8 pCm-1s2. The upper limit of the useful frequency range is about 1 kHz. It has directional sensitivity which reaches a maximum perpendicular to the plane of the crystal. With the esophageal microphone cardiovascular sound is recorded simultaneously with other tracings: external phonocardiogram, E.C.G., carotid pulse and M-mode echocardiogram. The great advantage of the application of the esophageal microphone is that it can be positioned in the esophagus close to the mitral valve and the left atrium by use of fluoroscopy, so that sounds and murmurs originating from that part of the heart are recorded in detail. In a case of a shunt between aorta and pulmonary artery the microphone was used at different levels in the esophagus, showing different amplitudes of a continuous murmur. In all other cases the probe was situated in the esophagus just above the level of the mitral valve behind the left atrium. In 2 cases the advantage of the esophageal microphone (revealing signs of slight mitral incompetence) over the body surface microphone is shown. In 3 patients with artificial valves in the aortic and mitral orifices (where left heart catheterisation and left ventricular angiography is a considerable risk), the esophageal microphone also improved the postoperative evaluation and diagnosis of mitral valve regurgitation considerably.
一种微型食管麦克风已被制造出来。它呈圆柱形，外径5毫米，长度25毫米。它是一种加速度计，可检测食管壁的振动。其共振频率为2.1千赫，加速度电荷灵敏度为2.8皮库仑每米每秒平方。有用频率范围的上限约为1千赫。它具有方向敏感性，在垂直于晶体平面的方向上达到最大值。使用食管麦克风可同时记录心血管声音与其他描记图：体外心音图、心电图、颈动脉脉搏和M型超声心动图。应用食管麦克风的一大优势在于，通过荧光透视检查，它能够放置在食管中靠近二尖瓣和左心房的位置，从而详细记录源自心脏该部位的声音和杂音。在一例主动脉与肺动脉分流的病例中，在食管的不同水平使用了该麦克风，显示出连续性杂音的不同幅度。在所有其他病例中，探头位于食管中左心房后方二尖瓣水平上方。在2例病例中，显示出食管麦克风（揭示轻微二尖瓣关闭不全迹象）相对于体表麦克风的优势。在3例主动脉瓣和二尖瓣口有人工瓣膜的患者中（左心导管插入术和左心室血管造影存在相当大风险），食管麦克风也显著改善了二尖瓣反流的术后评估和诊断。
