Alveolocapillary membrane permeability in experimental model of ventilator induced lung injury

Abstract

Aim: to assess alveocapillary membrane permeability for the whole protein, middle molecular peptides and some lipoperoxidation markers depending on respiratory volume using in reproduction of ventilator induced lung injury model.

Material and methods: Experiments were carried out on 15 laboratory rats- males (body mass 180–240 gr.) of “Vistar” line). The mechanical pulmonary ventilation in rats was carried out using tracheostomy cannula ALV Hamilton G 5 apparatus during 2 hours under the total anesthesia with sodium thiopental at a rate of 40 mg|kg of animal body mass. The initial parameters of ventilation were equal in all animals: Inspiratory time = 0,5 seconds; respiratory rate = 60 – 76/minute; pressure at the end of expiration (PEE) = 0 - 2 sm. of water column; inspiration-expiration ratio (I:E) = 1:1 or 1:2. Depending on the size of respiratory volume (RV) animal were divided into 3 groups (n=5). Animals with RV=7 ml/kg of body mass formed the first group (the control one). The second group included animals with RV = 20 ml/kg of body mass (the moderate volutrauma) and the third one included animals with RV = 40 ml/kg of body mass (the heavy volutrauma). The bronchoalveolar lavage was carried out on isolated lungs with the volume of filling at a rate 5 ml of 0,9 % sodium chloride solution for 1 g of pulmonary tissue and there was received nearly 2,5+0,5 ml of lavage liquid (sodium chloride solution + bronchoalveolar liquid). The alveolocapillary membrane permeability was assessed by detecting in the received liquid of bronchoalveolar lavage the concentration of whole protein on Lowry, the content of middle mass molecules on extinction at wave lengths 238, 254, 260, and 280 nm; the level of diene conjugates on V.B. Gavrilov and catalase activity on M.A. Koroliuk. The received data were processed using methods of nonparametric statistics. The revealed intergroup differences were assessed on Kruskall-Wallis «ANOVA» criterion. The differences at р < 0,05 were considered as reliable ones.

Results: Alveolocapillary membrane permeability for the whole protein at the size of respiratory volume 20 ml/kg of body mass exceeds the values in control group in 12,5 times and at respiratory volume 40 ml/kg- in 20 times. Alveolocapillary membrane permeability for middle molecular peptides at the size of respiratory volume 20 ml/kg exceeds the values in the control group on extinction at 238 nm in 2 times; at 254 nm in 1,5 times; at 260 nm in 1,2 times and at 280 nm in 1,5 times. The double increase of respiratory volume at reproduction of ventilator induced lung injury model is attended with practically double increase of alveolocapillary barrier permeability for middle molecular peptides determined by detection at all wave lengths. The changes of alveolocapillary membrane permeability for diene conjugates in the conditions of ventilator induced lung injury model correspond to the one for protein and middle molecular peptides. The change of catalase activity as alveolocapillary membrane permeability marker is informative only in the model used at respiratory volume 40 ml/kg of animal body mass.

Conclusions: The changes of alveolocapillary membrane permeability in ventilator induced lung injury model are proportional to the size of respiratory volume used for reproduction of the model