PEC EPE Biomedical key terms

A small voltage produced by living tissue, such as the heart, brain, or muscle, caused by the movement of ions across cell membranes. It is the signal that electrodes pick up for ECG, EEG, and EMG recordings.

The electrical boundary where a surface electrode contacts the body, behaving as a resistor and capacitor in parallel. Its impedance affects signal amplitude, noise pickup, and how well biopotentials are recorded.

The buildup of charge at an electrode-electrolyte boundary that creates a half-cell potential and opposes current flow. It can offset recorded signals and is reduced by using nonpolarizing silver-silver chloride electrodes.

The direct voltage that develops between an electrode and the electrolyte it touches, depending on the materials involved. Mismatched half-cell potentials at two electrodes appear as a DC offset in a recording.

Spurious signal caused by movement of electrodes, cables, or the patient, which alters electrode-skin contact and adds noise. Careful skin preparation, secure leads, and filtering help reduce it.

A measure of how well a differential amplifier suppresses a signal present equally at both inputs, compared with a signal that differs between them. Higher values mean better rejection of interference such as mains hum.

A precision differential amplifier with high input impedance, high gain, and high common-mode rejection. It is the standard front end for biopotential recording because it extracts tiny signals from noisy environments.

A narrow band-stop filter that attenuates a specific frequency, commonly 50 or 60 Hz, to remove power-line interference. It must be used carefully so it does not distort nearby signal components.

The recording of the heart's electrical activity from surface electrodes, displayed as an ECG waveform. Its P, QRS, and T waves support diagnosis of rhythm and conduction disorders.

The recording of electrical activity produced by skeletal muscle, either with surface or needle electrodes. It is used to assess neuromuscular function and to control prosthetic or assistive devices.

A device that delivers a controlled electrical shock to the heart to terminate life-threatening arrhythmias such as ventricular fibrillation. It may be manual, automated external, or implanted.

An implanted or external device that delivers electrical pulses to stimulate heart muscle and maintain an adequate rhythm. It senses intrinsic activity and paces when the rate falls below a set threshold.

Current that flows from a device through a patient to earth, which can be dangerous if it passes through the heart. Limits are set by safety standards and are tighter for cardiac-connected applications.

Electrical separation between circuits achieved with transformers, optocouplers, or capacitors so no direct conductive path exists. It protects patients from fault currents and blocks interference between device sections.

A very small current, on the order of microamperes, that reaches the heart directly through a conductive pathway such as a catheter. It can trigger fibrillation even though it is far below the threshold for skin contact.

Current that passes through the body via skin contact and is large enough to cause injury or disturb the heart. Thresholds are higher than for microshock because skin impedes current flow.

Unwanted electrical disturbance coupled into a device from external or internal sources such as motors, radio transmitters, or other equipment. It can corrupt signals or disrupt device operation.

A noninvasive method that estimates arterial oxygen saturation by comparing light absorption at red and infrared wavelengths across perfused tissue. It relies on the pulsatile component of the signal.

An optical technique that detects blood volume changes in tissue by measuring light transmitted or reflected. The resulting waveform underlies pulse oximetry and many wearable heart-rate monitors.

A sensor whose electrical resistance changes when it is stretched or compressed. Bonded to a diaphragm or beam, it converts pressure or force into an electrical signal in devices such as blood pressure transducers.

A circuit of four resistive arms used to measure small resistance changes precisely. In biomedical sensors it converts strain-gauge or thermistor changes into a voltage proportional to the measured quantity.

A resistor whose resistance varies strongly and predictably with temperature. It is widely used in medical devices for temperature measurement and compensation because of its high sensitivity.

A sensor that converts fluid or gas pressure into an electrical signal, often using a strain gauge on a diaphragm. It is central to invasive blood pressure monitoring and ventilator pressure control.

A published set of requirements limiting leakage current, insulation, and grounding for medical electrical equipment. Compliance is demonstrated through testing and is required for regulatory approval and clinical use.

The ratio of the wanted signal amplitude or power to the unwanted noise in a measurement. A higher ratio means the underlying physiological information is clearer and easier to interpret.

A low-pass filter placed before sampling to remove frequency components above half the sampling rate. Without it, high-frequency content folds back into the recorded band as aliasing distortion.

The number of samples taken per second when converting an analog signal to digital form. It must exceed twice the highest frequency of interest to avoid aliasing.

The ability of a material or device to perform its function in contact with living tissue without causing unacceptable harm. It is assessed through tests for toxicity, irritation, sensitization, and blood compatibility.

A validated process that destroys all viable microorganisms on a medical device before use. Common methods include steam autoclaving, ethylene oxide, gamma radiation, and hydrogen peroxide plasma.

A device intended to be used on one patient for one procedure and then discarded. Reusing it without validated reprocessing risks infection and degraded performance.

A medical device surgically placed inside the body for a prolonged period, such as a pacemaker, stent, or cochlear implant. It must meet strict requirements for biocompatibility, reliability, and hermetic sealing.

A statistical measure of the effective magnitude of a varying signal, equal to the square root of the mean of its squared values. It is commonly used to quantify AC voltages and currents.

The total opposition a circuit presents to alternating current, combining resistance and reactance. In biomedical measurements it determines signal transfer, noise coupling, and electrode performance.

A filter that passes low frequencies and attenuates those above a chosen cutoff. In biomedical instrumentation it removes high-frequency noise and prevents aliasing before sampling.

The process of comparing a measurement instrument's output against a known reference and adjusting it to reduce error. Regular calibration ensures readings are accurate and traceable.

Connecting a circuit or equipment chassis to a low-impedance earth reference to provide a safe return path for fault current. Proper grounding reduces shock hazard and electrical interference.