Laser Doppler Flow
Gas Concentration Measurement
BIOPAC Biopotential Amplifiers are specialized differential amplifiers designed to amplify the uV and mV level biopotentials that are generated by living organisms. Biopotentials are electrical signals (voltages) that are generated by physiological processes occurring within the body. Biopotentials are produced by the electrochemical activity of a type of cell, called an excitable cell. Excitable cells are found in the nervous, muscular and glandular systems in the body. When an excitable cell is stimulated, it generates an action potential, which is the essential source of biopotentials in the body.
The body sources other biopotentials that are not directly related to action potentials. Examples include the corneal-retinal (corneoretinal) potential, skin potential and the electromechanical behavior of bone. In addition, many physiological processes in the body contribute to measurable impedance changes. Impedance changes are sensed by applying external excitation signals that convert impedance to voltage. These phenomena are usually considered to be indirectly generated biopotentials. Examples include electrodermal activity (EDA), cardiac impedance (stroke volume) and thoracic impedance (respiration). Another class of indirectly generated biopotentials include those in which the physiological process acts to modulate light energy, versus electrical energy. Examples include the optical blood volume density (PPG or BVP) and blood oxygen level (SpO2).
When recording biopotentials at the body surface, typically many action potentials are juxtaposed, weighted and measured simultaneously. This is because the measurement electrodes are usually some distance from the activated volume and are large in comparison to the nerves and motor units under investigation. Furthermore, the activated tissue is surrounded by the volume conductor of the body. This surrounding volume conductor acts to variably superimpose and attenuate action potentials. Accordingly, surface biopotentials are usually 1mV or less, even though the source action potentials may be on the order of 100mV in p-p amplitude. With the use of fine wire or needle electrodes, however, measured biopotentials may be substantially higher than compared to surface electrodes. This result is primarily due to the proximity of electrodes to the activated volume and the increased specificity of smaller electrodes.
In the context of recording from living organisms, BIOPAC Biopotential Amplifiers are useful for measuring voltage signals present between a pair of measurement electrodes. Electrodes can be inserted into living tissue or placed on the exposed surface of tissue. Electrodes inserted into tissue, known as invasive electrodes, are typically fine wire or needle electrodes. Electrodes placed on the surface of tissue, or on the exterior of the body, are known as surface electrodes. The following biopotential amplifiers are suitable for recording from needle or surface electrodes:
ECG100C – Electrocardiogram Amplifier
Amplifies electrical activity generated by the heart and will reliably record ECG from humans, animals and isolated organ preparations. The ECG amplifier output can be switched between normal ECG output and R-wave detection. The R-wave mode outputs a smoothed pulse with the occurrence of each R-wave. The exact timing of the R-wave is detected even under conditions of extreme signal artifact. The amplifier also includes a user-switchable baseline stabilizer.
EEG100C – Electroencephalogram Amplifier
Amplifies biopotentials associated with neuronal activity of the brain and can be used to perform unipolar or bipolar EEG measurements. The amplifier output can be switched between normal EEG output and Alpha wave detection. The Alpha detection mode outputs a smoothed wave with a peak indicating maximal alpha activity (signal energy in the 8-13 Hz frequency range).
EGG100C – Electrogastrogram Amplifier
Amplifies the electrical signal resulting from stomach and intestinal smooth muscle activity. The amplifier monitors the DC potential on the skin surrounding, or surface of, the intestine and stomach, which is indicative of the degree of slow wave contraction. The amplifier permits DC coupling to electrodes for signal amplification and presentation without discernible decay.
EMG100C – Electromyogram Amplifier
Amplifies skeletal muscle electrical activity generated by motor unit action potentials (MUAPs). The amplifier incorporates fast response and settling time characteristics and is primarily used to measure multiple, superimposed MUAPs via non-invasive skin electrodes. The amplifier can be used to measure a single MUAP, using invasive fine wire electrodes. The amplifier is also suitable for measuring peripheral nerve action potentials, via surface, needle or fine wire electrodes.
EOG100C – Electrooculogram Amplifier
Amplifies the corneal-retinal potential associated with the eyes. The amplifier monitors the DC potential on the skin surrounding the eyes, which is proportional to the degree of eye movement in any direction. The amplifier output can be switched between normal EOG output and Derivative of EOG. In Derivative mode, the amplifier outputs the measured velocity of eye movement; which is useful for saccade and nystagmus investigations. The amplifier permits DC coupling to electrodes for X/Y graphing of eye movement without discernible decay.
ERS100C – Evoked Response Amplifier
Amplifies very small biopotentials, such as those associated with stimulus/response, signal averaged recordings. Selectable gain and bandwidth options make the evoked response module useful for a variety of evoked response testing applications. The amplifier is intended for use in applications such as auditory brainstem response, startle response, somatosensory evoked response or nerve conduction velocity recording.
These amplifiers incorporate the AD620 Instrumentation Amplifier, but employ different filtering selections, gain options and other signal processing methods to optimize specific biopotential signal measurement. These amplifiers have high Common Mode Rejection Ratio (CMRR) and Common Mode Input Impedance (CMII) over a wide frequency range. A specialized front end is employed which permits the amplifier to operate in two terminal mode, allowing the amplifier to measure a biopotential signal without the use of a third lead, to the subject, to provide bias. This front end also employs a common mode feedback drive signal to boost CMII, improve CMRR and provide for driven shield operation. The amplifiers are configurable and can operate in a variety of measurement scenarios, including:
1. Bipolar Mode: Standard differential biopotential measurement
2. Unipolar Mode: Active input is measured with respect to a common reference
3. Two Terminal – Ungrounded biopotential measurements
4. Three Terminal – Grounded biopotential measurements
5. Driven Shield Mode – Input line shields are driven by a buffered common mode reference to enhance CMII and CMRR
6. Grounded Shield Operation – Input shield lines are held at ground for lowest possible noise
BIOPAC Transducer Amplifiers are specialized differential amplifiers designed to amplify small signals generated by physiological activity. Transducer Amplifiers provide an excitation source that activates the measurement substrate to allow the generation of a voltage signal indicative of the physiological signal of interest. In some cases, the measurement substrate is the organism itself, and in other cases a transducer is used that converts one form of activity into a variable impedance.
EBI100C – Electrical Bioimpedance Amplifier
Amplifier records the parameters associated with impedance cardiography, cardiac output measurements, thoracic impedance changes as a function of respiration or any kind of biological impedance monitoring. Incorporates a high frequency current source that injects a small current through the measurement tissue volume defined by the placement of a set of current source electrodes. A separate set of voltage monitoring electrodes measures the potential developed across the tissue volume. Because the current is constant, the voltage measured is proportional to the characteristics of the biological impedance of the tissue volume. The amplifier measures both the impedance magnitude and phase of the tissue volume under test.
EDA100C – Electrodermal Activity Amplifier
Amplifier measures both the skin conductance level (SCL) and skin conductance response (SCR) as they vary with sweat gland (eccrine) activity due to stress, arousal or emotional excitement. The EDA100C uses a constant voltage (0.5 V) technique to measure skin conductance. The controls allow selection of absolute (SCL+SCR) or relative (SCR) skin conductance measurements.
NICO100C – Non-invasive Cardiac Output Amplifier
Amplifier records specific parameters associated with cardiac output measurements. Incorporates a high frequency current source that injects a small measurement current through the thoracic volume defined by the placement of a set of current source electrodes. A separate set of voltage monitoring electrodes measures the potential developed across the thorax volume. Because the current is constant, the voltage measured is proportional to the impedance characteristics of the thorax. When directed through the thorax, the measurement current seeks the shortest and most conductive pathway. Consequently, the measurement current flows through the thoracic aorta and vena cava superior and inferior. The amplifier measures both the impedance magnitude and derivative of impedance of this thoracic volume under test. These impedance measures have a defined relationship to left ventricular aortic blood flow.
PPG100C – Photoplethysmogram Amplifier
The Photoplethysmogram Amplifier records the pulse pressure wave and provides an indication of blood pressure, blood density or vasoconstriction. Front panel controls allow selection of either absolute or relative plethysmographic measurements.
The Amplifier couples to a photoplethysmogram (PPG) transducer to record the blood volume pulse waveform via optical (photoplethysmogram) methods. A PPG transducer consists of a matched infrared emitter and photo diode detector, which transmits changes in infrared reflectance resulting from varying blood flow. Blood is highly reflective of near infrared light wavelengths, due to the heme subunit of hemoglobin. When the PPG transducer is placed on the skin, in proximity to capillaries, the reflectance of the infrared light from the emitter to the detector will change in accordance to capillary blood volume. The PPG waveform peaks when capillary blood volume is maximized.
RSP100C – Respiration Amplifier
The Respiration Amplifier is designed for direct physical measurement of respiratory effort. The Amplifier works with the TSD201 respiratory effort transducer to measure abdominal or thoracic expansion and contraction while breathing. The RSP100C permits DC coupling to transducer the for the recording of respiratory effort signals of arbitrarily low frequency. Front panel controls allow selection of absolute or relative expansion/contraction measurements. The respiratory waveform peaks at maximum inspiration and minimizes at full expiration.
SKT100C – Skin Temperature Amplifier
The SKT100C measures surface, core or air temperature. The SKT100C, with a TSD202 series temperature probe, can record temperature changes to 0.0001 deg C resolution. Front panel controls allow selection for either absolute or relative temperature measurements. The SKT100C operating temperature range is 40 deg F to 140 deg F (5 deg C to 60 deg C). Use the AcqKnowledge software to calibrate the SKT100C’s output in deg F or deg C.
BIOPAC Stimulation Units encompass a range of capabilities. Some stimulators produce pulsatile stimulation only, whereas others permit arbitrary waveform stimulation. Some stimulators are designed for voltage stimulation, while others can perform both voltage and current stimulation. The stimulators also offer a range of output energy producing capabilities.
The harmonized, international regulatory standard relating to the safety of nerve and muscle stimulators is IEC 601-2-10. Certain stimulation equipment is excluded from this standard, such as stimulators intended for cardiac defibrillation. Section 51.104 of the IEC 601-2-10 standard specifies the limitation of output power for a variety of wave types:
1. For stimulus pulse outputs, the maximum energy per pulse shall not exceed 300mJ, when applied to a load resistance of 500 ohms.
2. For stimulus pulse outputs, the maximum output voltage shall not exceed a peak value of 500V, when measured under open circuit conditions.
STM100C – Stimulator Driver Module
The Stimulator Driver Module provides pulse and waveform stimulus outputs for nerve conduction, evoked response, audio stimulus-response (e.g. startle response) and somatosensory response studies. The Stimulator Driver setup in AcqKnowledge provides single-, double- or multiple-pulse sequence outputs of any polarity. The Stimulator setup screen also provides standard sine, triangular and square wave outputs for other kinds of physiological tests. Alternatively, AcqKnowledge can be used to create an arbitrary waveform and then output it through the Stimulator Driver.
STMISOC – Isolated Stimulator, Bipolar Voltage, Unipolar Current
The STMISOC can stimulate with pulse, sinusoidal or arbitrary waveforms and is suitable for nerve conduction, muscle twitch, somatosensory stimulation, or other response studies requiring a stimulus. The Isolated Stimulator plugs into the STM100C to provide either an isolated voltage or constant current stimulus and incorporates a selectable linear voltage multiplier to amplify the voltage signal from the STM100C. Voltage stimulation can be unipolar or bipolar, with a maximum voltage output of 200 volts. Current stimulation is unipolar only, with a maximum compliance of 200 volts, and 12 preset constant current levels are provided.
STMISOLA – Linear Isolated Stimulator, Arbitrary Voltage and Current
The STMISOLA Constant Current and Constant Voltage Isolated Linear Stimulator provides flexibility in stimulation protocols and will connect to any analog output signal drive (±10 V input). The STMISOLA can be used to generate stimulation signals that can have arbitrary waveshape. The STMISOLA can output unipolar or bipolar arbitrary waves such as pulse (single or train), square, sine, triangle, exponentially decaying, modulated envelopes, and fully-arbitrary, user-specified types.
STM200 – Constant Voltage Unipolar Pulse Stimulator
The Constant Voltage Unipolar Pulse Stimulator has digital display, a keyed voltage range switch and software-controlled pulse width and repetition, with fully-arbitrary pulse sequence ability.
Laser Doppler Flow
LDF100C – Laser Doppler Flow Module
The LDF100C is a laser Doppler tissue perfusion monitor for measuring micro-vascular blood flow in tissue. The LDF100C amplifier delivers a low power beam of laser light down an optical fiber to the tissue being studied; typically, the volume of tissue sampled by the light is in the order of 1mm3. The LDF100C amplifier analyzes the Doppler shift created by moving red blood cells and outputs a channel indicating blood flow expressed in Blood Perfusion Units (BPU). On a second channel the LDF100C simultaneously outputs the tissue remittance (Backscatter) from 0 to 100%. The LDF100C employs the TSD140 series laser Doppler flow probes.
Gas Concentration Measurement
CO2100C – Carbon Dioxide Measurement Module
The CO2100C module records quickly varying carbon dioxide concentration levels. This fast-response analyzer is suitable for monitoring time-averaged carbon dioxide levels using mixing chambers or real-time levels for breath-by-breath measurements. The CO2100C module interfaces (via the AFT20 gas sampling interface kit) with the AFT15A and AFT15B mixing chambers, the AFT21 and AFT22 non-rebreathing T valves or the AFT25 mask with integral non-rebreathing T valve. The CO2100C module is equipped with a variable speed pump to adjust the air flow for a range of sampling conditions. The module uses a single beam infrared, single wavelength measurement technique. Sampling line connections for input and output flow are accessible (Luer type) on the front panel of the module.
O2100C – Oxygen Measurement Module
The O2100C module records quickly varying oxygen concentration levels. This fast-response analyzer is suitable for monitoring time-averaged oxygen levels using mixing chambers or real-time levels for breath-by-breath measurements. The O2100C module interfaces (via the AFT20 gas sampling interface kit) with the AFT15A and AFT15B mixing chambers, the AFT21 and AFT22 non-rebreathing T valves, or the AFT25 mask with integral non-rebreathing T valve. The O2100C module is equipped with a variable speed pump to adjust the air flow for a range of sampling conditions. The module employs an analysis technique based on the parametric oxygen measurement principle. Sampling line connections for input and output flow are accessible (Luer type) on the front panel of the module.