Effects of Artefacts on ECG Recording Abnormal patterns of ECG may be due to pathological states or on occasion they may be due to artefacts. To diagnose the presence of undesirable artefacts on the ECG trace, a few recordings are illustrated below: فقط التأثيرات نقاط تعداد مع مثالك Interference from the Power Line: Power line interference is easily recognizable since the interfering voltage in the ECG would have a frequency of 50 Hz. This interference may be due to the stray effect of the alternating current on the patient or because of alternating (b) current fields due to loops in the patient cable. Other causes of interference are loose contacts on the patient cable as well as dirty electrodes. When the machine or the patient is not properly grounded, power line interference may even completely obscure the ECG waveform. ECG recording with regular spreading of the curve with super imposed 50 Hz power line interference signals. Recording with irregular trembling of the ECG trace without wandering of the base line but otherwise normal ECG trace. This noise is very difficult to remove except in those machines which have very high CMRR. The noise can be reduced by partially shielding the patient by means of the bed springs. Connection of the springs to the instrument case helps to compensate for a poor CMRR. 30 Assist Lec: Athra'a Sabeeh 1st Semester 2023-2 Electromagnetic interference from the power lines also results in poor quality tracings. Electrical equipment such as air-conditioners. elevators and X-ray units draw heavy powerline current, which induce 50 Hz signals in the input circuits of ECG machines. Due to unbalanced linkages, common mode rejection circuits almost prove ineffective against them. A practical solution to minimize this problem is physical separation between the interference causing sources and the patient. Shifting of the Baseline A wandering baseline but otherwise normal ECG trace is usually due to the movement of the patient or electrodes. The baseline shift can be eliminated by ensuring that the patient lies relaxed and the electrodes are properly attached. Baseline wander is usually observed immediately after application of
Effects of Artefacts on ECG Recording Abnormal patterns of ECG may be due to pathological states or on occasion they may be due to artefacts. To diagnose the presence of undesirable artefacts on the ECG trace, a few recordings are illustrated below: فقط التأثيرات نقاط تعداد مع مثالك Interference from the Power Line: Power line interference is easily recognizable since the interfering voltage in the ECG would have a frequency of 50 Hz. This interference may be due to the stray effect of the alternating current on the patient or because of alternating (b) current fields due to loops in the patient cable. Other causes of interference are loose contacts on the patient cable as well as dirty electrodes. When the machine or the patient is not properly grounded, power line interference may even completely obscure the ECG waveform. ECG recording with regular spreading of the curve with super imposed 50 Hz power line interference signals. Recording with irregular trembling of the ECG trace without wandering of the base line but otherwise normal ECG trace. This noise is very difficult to remove except in those machines which have very high CMRR. The noise can be reduced by partially shielding the patient by means of the bed springs. Connection of the springs to the instrument case helps to compensate for a poor CMRR. 30 Assist Lec: Athra'a Sabeeh 1st Semester 2023-2 Electromagnetic interference from the power lines also results in poor quality tracings. Electrical equipment such as air-conditioners. elevators and X-ray units draw heavy powerline current, which induce 50 Hz signals in the input circuits of ECG machines. Due to unbalanced linkages, common mode rejection circuits almost prove ineffective against them. A practical solution to minimize this problem is physical separation between the interference causing sources and the patient. Shifting of the Baseline A wandering baseline but otherwise normal ECG trace is usually due to the movement of the patient or electrodes. The baseline shift can be eliminated by ensuring that the patient lies relaxed and the electrodes are properly attached. Baseline wander is usually observed immediately after application of
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