Effects of inflammatory mediators and mechanism of dynamic factors on lung injury in a dog model of a-cute respiratory distress syndrome

Abstract

Objective To evaluate the effect on inflammatory mediators and mechanism of dynamic factors on lung injury in a dog model of acute respiratory distress syndrome (ARDS). Method The ARDS dog model was duplicated by instillation hydrochloric acid. The dogs were randomly (random number) divided into six groups: (1) normal control group (N group); (2) ARDS group (M group); (3) low VT (6 mL/kg) at respiratory rate 30, low inspiratory flow 6 mL/(kg·s). (4) large VT (20 mL/kg) at respiratory rate 30, high inspiratory flow 20 mL/kg·s.(5) large VT (20 mL/kg) at respiratory rate 15, high inspiratory flow 17 mL/(kg·s). (6) large VT (20 mL/kg) at respiratory rate 15, low inspiratory flow 10 mL/(kg·s). All the dogs were killed after 4 h ventilation. TNF-α、IL-8, p38 MAPK and NF-κB activity in the lung were measured. Results The expression of IL-8 protein in B and C groups was much higher than that of other groups ( P 0.05). The gray scale ratio of B group was obviously higher than that of other groups (P 0.05). There was no significant changes among M, A and D groups in TNF-α protein contents. p38 MAPK value of positive staining of B group was the strongest, significantlyhigher than that of D group ( P < 0.01) .The expression of p38 MAPK in B and C groups was much higher than other groups (P <0.01). NF-κB activity in B group (33.56±2.85%) was significantly higher than that in A (10.35±0.6%)、D(7. 11 ± 0.47%)group, but there was no difference between B and C group (30.87 ± 1.16%). Conclusions Ventilation at high tidal volume, high inspiratory flow rate, high respiratory rate could activate p38 MAPK and increase the activity of NF-κB with the result of aggravating the release of inflammatory mediators. p38 MAPK and NF-κB activation are the major mechanisms in the development of VILI. Key words: Ventilator-induced lung injury; Acute respiratory distress syndrome; Dynamic factors; Inspiratory flow