Double-Chamber Plethysmograph Box

This setup has been specially developed for the investigation of bronchospasmolytically active substances on the conscious guinea pigs up to 450 g (restrainer 73-3951 included) or on small rats (special restainer 73-2469 required) according to PENNOCK. Can also be used as head-out box. Inner diameter of standard restrainer (guinea pig) is 70 mm.

• Specific Airway Resistance measurement together with the standard parameters tidal volume and respiratory rate, in conscious animals
• Software controlled multiple animal version (up to 4 boxes)
• Aerosol challenge software controlled
• Applications
  • Toxicology
  • Environmental studies
  • Long term drug effects

Parameters Measured

The following parameters are determined:

From the flow signal of the thoracic chamber:

• Peak Inspiration Flow
• Peak Expiration Flow
• Tidal Volume
• Minute Volume
• Respiration Rate 

Optionallly:

• Duration of Inspiration
• Duration of Expiration
• Apnea Time
• Time of brake
• Time of pause
• Airflow at 0.5TV

From the time displacement between nasal and thoracic flow:

• Phase Displacement Q
• Specific Airway Resistance

How It Works

The animal is placed into the double chamber and is restricted so that the head protrudes into the front chamber. The neck is sealed with a soft diaphragm. The nasal air flow is measured in the front chamber, thethoracic respiratory flow in the rear chamber. Both measurements aremade with measurement screens and differential pressure transducers.

There is a phase shift between the two respiratory flows from which the specific airway resistance according PENNOCK can be calculated. For recording and evaluation the HSE respiratory software PENNOCK is used. The thoracic chamber can be removed and the animal can easily be placed into position. The chamber is available with two different restrainers to suit different size animals.

The nasal chamber is connected to the bias flow venturi-jet tube (requires compressed air) and the oxygen flushing (supply required). The aerosol nebulizer connected to the nasal chamber is a jet nebulizer. It requires an operating pressure of about 1.5 bar (21.75 PSI). Ports are provided on both chambers for calibration so that a defined volume can be introduced witha syringe. The pressure transducers are connected to two amplifiers.

The important parameter is the specific airway resistance which is determined from the phase shift between the nasal and the thoracic flow. The PENNOCK software is able to analyze the signals and control the valves from 4 plethysmograph boxes. The advantage of the control system is that no mistakes occur in manual settings of valves. Furthermore, the animal in the chamber is not frightened by handling the valves. The PLUGSYS system is used to interface the boxes to the computer. The PLUGSYS housing supports the TAM-A preamplifiers for the differential low pressure transducers. A special module PCU“Plethysmograph Control Unit” for the automatic control of the different valves has been developed and must be installed in the PLUGSYS housing. One housing takes all the modules for a 2-channel system. For a 4-channel system two PLUGSYS housings are required.

Each plethysmograph box is equipped with 4 special membrane valves. These valves replace the stopcocks and have to be set to specific positions depending on the operating phase (measure, challenge, flush).The membrane valves need compressed air for operation. The PCU module supplies the valves and must therefore be connected to a compressed air supply (2-10 bar) (29-145 PSI). The PCU module also produces the vacuum for the bias flow and operates the oxygen flow for flushing (an oxygen supply at a pressure of 6 bar (87 PSI) max. is required)and the compressed air for the nebulizer. The PCU module is connected to each box through 6-way ribbon tubing.

The PCU module can be computer controlled. The software automatically operates the various valves at the appropriate timing. A manual control box provides manual control of the different phases. The manual control and the software control have equal priority.