Pressure
Control and Measurement

Model PS/200

This Pressure Servo and Peristaltic Pump instrument has two modes of operation.

Pressure mode - Establishes and automatically maintains any selected pressure between 0 and 200 mmHg.
Flow mode - Produces an adjustable, stable perfusion rate in the range of 3 µl/min to 2.5 ml/min.

A solid-state pressure transducer placed in a biological preparation setup, such as a cannulated vessel, senses the pressure for control of the miniature peristaltic pump. This pump supplies physiological perfusates from a reservoir to generate and hold a particular pressure, or flow; each can be independently determined by the setting of pre-calibrated dials. Pressure is indicated directly in mmHg on a digital panel meter in both modes, and is available as an analog output voltage for data acquisition. Pressure may also be programmed through an external voltage signal applied to the instrument. Additional information can be found in Q&A.

Specifications of the PS/200

Perfusion Pressure Monitor

Measure and Record -

• Two Pressures
  • Pressure Difference
    • Pressure Average

Model PM/4

This instrument is ideally suited for isolated, perfused vessel studies to aid the investigator in ensuring that a perfused vessel is exposed to a desired physiological pressure. It can also be used for measuring the pressures at two locations in a vessel bed or isolated tissue. In conjunction with the Pressure Servo and Peristaltic Pump, PS/200, a transmural vessel pressure or a perfusion pressure may automatically be maintained during perfusion.

A simple procedure is used to calibrate the four pressure signals directly in mmHg. These pressure signals can be simultaneously sent to a recorder or data acquisition system while selectively monitoring any one of the four pressures on the meter. Two pressure transducers with Luer fittings and output cables for the four signals are supplied with the instrument. Also, see Q&A.

Specifications

• Digital Meter: 0 - 200 mmHg; 1 mmHg resolution; ± 1% linearity; 3 samples/s
• Analog Outputs: 10 mV/mmHg; 0 - 300 mmHg; <15 ms response time; ± 1% linearity
• Pressure Transducers: 0.04 mm3/100mmHg volume displacement
• Size: 6.5 x 14.5 x 17.5cm (H x W x L); Weight: 0.3 kg ·
• Power: 100 -120 V/60Hz or 200 - 240 V/50Hz

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Extravascular Pressure Control System

Function – The instruments provide a means for applying extravascular pressures (EvP) to excised, cannulated and pressurized vessels mounted in a sealed chamber. In particular, for cardiac, skeletal muscle and other vessels subjected to sustained or pulsatile pressures from the muscular tissue in which they are embedded. Studies can be carried out on these vessels to determine whether the functional changes that often occur may have local or distal significance in cardiovascular disease, and for analyzing underlying mechanisms.

System Components – The two instruments explained in more detail below are the Extravascular Pressure Control, Model EV-1 and the Signal Generator, Model SG-1. Briefly, the EV-1 produces selectable, sustained EvP when used alone, and acts as an intermediate link allowing the SG-1 to create sinusoidal and pulsatile extravascular pressure waveshapes.

          The sealed vessel chambers, Model CH/1/AU or its self-heated cousin Model CH/1/AU/SH are key components of this system. These chambers are described elsewhere on our website.

          A laboratory compressed gas tank and a regulating valve (user supplied) for reducing the pressure to 6 to 8 psi is the fundamental source of system pressure. It is then modified by signals received from the EV-1 via the Electronic Servo Valve to create the desired steady or non-steady extravascular chamber pressures. The servo valve is included as part of the EV-1.

  

EV – 1 Pressure Control Unit –

           The extravascular pressure (EvP) in the sealed chamber is sensed by a solid-state pressure transducer. The signal from this transducer is connected to the EV-1 Control Unit where it is compared with either the internal pressure signal set by the EV-1 pressure dial, or one of the external pressure signals fed into either the Function Generator or Signal Generator input jacks. Any difference between these two signals regulates the Electronic Servo Valve output pressure so that the two presures are the same.

Internal Pressure Signal Mode:  Here, the signal corresponding to the Pressure Dial setting calibrated in mmHg establishes the extravascular chamber pressure. This pressure is sustained until a new presure is selected. The panel meter reading also shows the chosen extravascular pressure in mmHg which can be accessed for data acquisition at the rear panel Pressure Signal jack.

External Pressure Signal Mode: When switched to this mode, various  extravascular pressure waveshapes can be created to match external input signals. Again, the actual extravascular pressure can be accessed for data acquisition at the rear panel Pressure Signal jack.

 Function Generator signals can be obtained from a computer program written by the user and a computer having a D/A computer board that supplies analog voltages of 10 mV/mmHg. In this way, various simple or complex, time-dependent pressures can be applied to the chamber.

Signal Generator – The Model SG-1 is used to establish sinusoidal and pulsatile extravascular waveshapes as described ahead.

 

SG-1 Signal Generator -

          This instrument provides extravascular Sinusoidal or Pulse pressure (EvP) waveshape signals as shown below to the sealed chamber via a cable connection to the EV-1 when used in external signal mode. User-friendly pushbuttons are used to program upper and lower limits of the pressures as well as pulses per minute and other parameters that may best suit the experimenter’s protocol. In both the Sine and Pulse Modes pulse rates can be selected as appropriate for humans or for small animals.