An isolated blood-perfused guinea-pig lung model for simultaneous registration of haemodynamic, microvascular and...

We have developed an optimized isolated lung perfusion system, which possesses several advantages. Firstly, studies of microvascular, respiratory, haematological and biochemical variables are combined in one model. Secondly, blood perfusion resulted in less oedema formation than buffer-perfused lungs, and high PO2 through ventilation with room air. Finally, data for the variables can be displayed, controlled and recorded in real time using a computerized system permitting subsequent processing (e.g. filtering without destroying original data). In this paper we discuss the basic behaviour of the model in terms of vascular resistance, vascular permeability, respiration and neutrophil sequestration. In addition, the effects of oleic acid, histamine and histamine receptor blockers were tested, and two methods of calculating vascular permeability are discussed. The way in which different anaesthetics affect the neutrophil content of lung tissue and blood was also investigated. In the model, oleic acid increased pulmonary vascular resistance and permeability, whereas histamine did not affect either permeability or the pre/postcapillary vascular resistance ratio. However, histamine receptor blockers increased this ratio, indicating that there was endogenous histamine release. The neutrophil content of the isolated lungs was increased, but this did not affect the variables measured. There was also accumulation of neutrophils in the lungs of blood donor animals, due to CO2 sedation. However, CO2 sedation proved to be superior to pentobarbital or ketamine anaesthesia in maintaining the levels of neutrophils circulating in the blood. In conclusion, this model seems to be sensitive and to yield reproducible results regarding the physiology or pathophysiology of the lung.