- For bronchial overflow measurements on Rat or Guinea-Pig
- Alternative method to Einthoven
- No risk of overpressure ventilation
- More physiological and safer than Einthoven test
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This classical method is an improvement on the Einthoven tracheal pressure measurement. Here the anesthetized animal is again ventilated with a STARLING pump. The respiratory stroke volume has to be set initially so that about 30% of the pump stroke is not taken up by the respiratory tract after inflation of the lung. This volume escapes from the system as overflow and is measured by a pneumotachometer. This arrangement is selected so that the pressure is limited by an adjustable water column. Drugs with bronchospastic or broncholytic action increase or reduce the overflow. A Y-shaped tracheal tube is linked to a STARLING pump, e.g. Harvard 683 Rodent Ventilator. The expiratory outlet of the respiration pump is connected to an immersion tube so that a positive end-expiratory pressure (PEEP) of about 1 cm water column is produced. The inspiratory pressure is limited to about 10 cm water column by a further immersion tube connected in parallel with the respiratory cannula. The overflow (i.e. the air volume not taken up by the lungs) is measured by means of a pneumotachometer (Fleisch tube) No. 000 or PTM and recorded by a differential pressure transducer as air flow in ml/sec. This air flow is also integrated to determine the air volume against time. It is of course necessary to ventilate the animal with a sufficiently large volume, e.g. 1.5 times its tidal volume.
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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