Pressler Gary A, Mansfield Jeffrey P, Pasterkamp Hans, Wodicka George R
Department of Biomedical Engineering, Purdue University, West Lafayette, IN 47907-2022, USA.
IEEE Trans Biomed Eng. 2004 Dec;51(12):2089-96. doi: 10.1109/TBME.2004.836525.
Several clinical and ambulatory settings necessitate respiratory monitoring without a mouthpiece or facemask. Several studies have demonstrated the utility of breathing sound measurements performed on the chest or neck to detect airflow. However, there are limitations to skin surface measurements, including susceptibility to external noise and transducer motion. Thus, this two-part study investigated a novel location for breathing sound measurements: the external ear. The first study investigated characteristics of sound transmission from the oropharynx to the external ear in 19 adults (nine males). Broadband noise was directed into the oropharynx through a tube and mouthpiece and measured indirectly via an accelerometer affixed to the cheek. Resultant transmission to the external ear was measured with a microphone inserted into an earplug that provided acoustic isolation from ambient noise. Near-unity coherence estimates (> 0.9) between the sounds recorded at the external ear and the oropharynx were observed up to approximately 800 Hz, indicating a low-frequency region of preferred transmission. In the second study, each of 20 subjects (nine males) breathed through a pneumotachograph at targeted shallow (3.0 mL/s/kg) and tidal (7.5 mL/s/kg) flows normalized to body mass, and the resulting sounds were recorded at the external ear. Recordings during breath hold measured background noise. Shallow and tidal expiratory flows, respectively, produced signal-plus-noise-to-noise [(S + N)/N] ratios of 6.7 +/- 4.1 dB and 14.0 +/- 5.3 dB (mean +/- standard deviation) across all subjects between 150 and 300 Hz. Concurrent inspiration demonstrated (S + N)/N ratios of 6.6 +/- 3.9 dB and 14.9 +/- 6.3 dB. Thus, the external ear shows promise as an anatomic site to detect and monitor breathing in a relatively noninvasive and unobtrusive manner.
在一些临床和门诊环境中,需要在不使用口含器或面罩的情况下进行呼吸监测。多项研究已证明,在胸部或颈部进行呼吸音测量对于检测气流具有实用性。然而,皮肤表面测量存在局限性,包括易受外部噪音和传感器移动的影响。因此,这项分为两部分的研究调查了一个用于呼吸音测量的新位置:外耳。第一项研究调查了19名成年人(9名男性)从口咽到外耳的声音传播特性。宽带噪声通过一根管子和口含器导入口咽,并通过贴在脸颊上的加速度计进行间接测量。通过插入耳塞的麦克风测量外耳的声音传输,该耳塞可与环境噪声实现声学隔离。在外耳和口咽记录的声音之间,在高达约800 Hz的频率范围内观察到接近一致的相干估计值(>0.9),表明存在一个优先传输的低频区域。在第二项研究中,20名受试者(9名男性)每人通过呼吸速度描记器以根据体重标准化的目标浅呼吸(3.0 mL/s/kg)和潮气量呼吸(7.5 mL/s/kg),并在外耳记录产生的声音。屏气期间的记录测量背景噪声。在所有受试者中,浅呼气流量和潮气量呼气流量在150至300 Hz之间分别产生信号加噪声与噪声之比[(S + N)/N]为6.7 +/- 4.1 dB和14.0 +/- 5.3 dB(平均值 +/- 标准差)。同时吸气时的(S + N)/N之比为6.6 +/- 3.9 dB和14.9 +/- 6.3 dB。因此,外耳有望成为以相对无创和不引人注意的方式检测和监测呼吸的解剖部位。