Ventilation
The lung is placed in the artificial thoracic chamber and ventilated at negative pressure, it is connected via the tracheal cannula to the pneumotachometer for measurement of respiratory flow. The humidified ventilation medium (air or gas mixture) is constantly flowing past the distal end of the pneumotachometer.
Perfusion
Lungs can be perfused by either constant flow or constant pressure. Although constant flow perfusion may mimic the in vivo situation more closely, it has the disadvantage that hydrostatic edema becomes inevitable during vasoconstriction. Constant pressure perfusion permits higher perfusate flow rates since vasoconstriction decreases perfusate flow and hydrostatic edema is less likely to occur.
Can be configured in one of three different perfusion modes:
1. Constant Flow Perfusion
2. Constant Pressure Perfusion
3. Dual System to Switch from Constant Flow to Constant Pressure and Vice Versa
Lung Weight Changes
Continuous measurement of weight changes of the lung is required for monitoring edema formation. This is possible during negative pressure ventilation inside the thoracic chamber by using the HSE-Edema balance LS 30 (weight transducer) (BS4 73-0593), range ±30 g, displacement 2 µm/gram. Weight changes induced by raising or lowering the perfusion pressure can be used to assess vascular permeability by determining the filtration coefficient.