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This setup has been specially developed for
the investigation of bronchospasmolytically active substances
on the conscious animal.
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, the thoracic respiratory flow in the rear chamber.
Both measurements are made 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
PULMODYN ‘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 with a syringe. The
pressure transducers are connected to two carrier amplifiers.
The following parameters are determined:
The important parameter is the specific airway
resistance which is determined from the phase shift between the
nasal and the thoracic flow.
The PULMODYN “PENNOCK” software is able to analyse the
signals from 4 plethysmograph boxes and to control the valves
of up to four 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 CFBA preamplifiers for the Validyne
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.
References:
1) PENNOCK, B.E., C.P.COX, R.M.ROGERS, W.A.CAIN and J.H.WELLS:
A non-invasive technique for measurement of changes in specific
airway resistance. J.Appl.Physiol. 46, 399 (1979)
2) PENNOCK, P.E.: A double flow body plethysmograph
for measuring specific airflow
conductance (unpublished)
3) SCHLEGELMILCH, R.: Respiratory measurements on conscious guinea-pigs using a double chamber plethysmograph box with aerosol challenge. FFB7 Cardiovascular and respiratory in vivo studies, 1991. Publ. by Biomesstechnik-Verlag March, D-79232 March, Germany
HUGO SACHS ELEKTRONIK-HARVARD
APPARATUS GmbH
Gruenstrasse 1 · D-79232 March-Hugstetten · GERMANY
Phone: +49 (0) 76 65 - 92 00-0 · Fax: +49 (0) 76 65 - 92
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