Dotsinsky Ivan
Center of Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 105, 1113 Sofia, Bulgaria.
Biomed Eng Online. 2005 Nov 26;4:65. doi: 10.1186/1475-925X-4-65.
Public access defibrillators (PADs) are now available for more efficient and rapid treatment of out-of-hospital sudden cardiac arrest. PADs are used normally by untrained people on the streets and in sports centers, airports, and other public areas. Therefore, automated detection of ventricular fibrillation, or its exclusion, is of high importance. A special case exists at railway stations, where electric power-line frequency interference is significant. Many countries, especially in Europe, use 16.7 Hz AC power, which introduces high level frequency-varying interference that may compromise fibrillation detection.
Moving signal averaging is often used for 50/60 Hz interference suppression if its effect on the ECG spectrum has little importance (no morphological analysis is performed). This approach may be also applied to the railway situation, if the interference frequency is continuously detected so as to synchronize the analog-to-digital conversion (ADC) for introducing variable inter-sample intervals. A better solution consists of rated ADC, software frequency measuring, internal irregular re-sampling according to the interference frequency, and a moving average over a constant sample number, followed by regular back re-sampling.
The proposed method leads to a total railway interference cancellation, together with suppression of inherent noise, while the peak amplitudes of some sharp complexes are reduced. This reduction has negligible effect on accurate fibrillation detection.
The method is developed in the MATLAB environment and represents a useful tool for real time railway interference suppression.
公众可获取的除颤器（PAD）现可用于更高效、快速地治疗院外心脏骤停。PAD通常由未受过训练的人员在街道、体育中心、机场及其他公共场所使用。因此，自动检测室颤或排除室颤至关重要。火车站存在特殊情况，那里电力线频率干扰显著。许多国家，尤其是欧洲，使用16.7赫兹的交流电源，会引入高水平的频率变化干扰，可能影响颤动检测。
如果移动信号平均对心电图频谱的影响不大（不进行形态学分析），则常将其用于抑制50/60赫兹干扰。如果能持续检测干扰频率，以便同步模数转换（ADC）以引入可变采样间隔，这种方法也可应用于铁路环境。更好的解决方案包括额定ADC、软件频率测量、根据干扰频率进行内部不规则重采样、对恒定样本数进行移动平均，然后进行常规反向重采样。
所提出的方法可完全消除铁路干扰，同时抑制固有噪声，而一些尖锐复合波的峰值幅度会降低。这种降低对准确的颤动检测影响可忽略不计。
该方法是在MATLAB环境中开发的，是实时抑制铁路干扰的有用工具。
