Resumo

BUENO, P.C.S. et al. Ventilation with high tidal volume induces inflammatory lung injury. Braz J Med Biol Res [online]. 2002, vol.35, n.2, pp. 191-198. ISSN 1414-431X.  http://dx.doi.org/10.1590/S0100-879X2002000200007.

Mechanical ventilation with high tidal volumes (V_T) has been shown to induce lung injury. We examined the hypothesis that this procedure induces lung injury with inflammatory features. Anesthetized male Wistar rats were randomized into three groups: group 1 (N = 12): V_T = 7 ml/kg, respiratory rate (RR) = 50 breaths/min; group 2 (N = 10): V_T = 21 ml/kg, RR = 16 breaths/min; group 3 (N = 11): V_T = 42 ml/kg, RR = 8 breaths/min. The animals were ventilated with fraction of inspired oxygen of 1 and positive end-expiratory pressure of 2 cmH₂O. After 4 h of ventilation, group 3, compared to groups 1 and 2, had lower PaO₂ [280 (range 73-458) vs 517 (range 307-596), and 547 mmHg (range 330-662), respectively, P<0.05], higher wet lung weight [3.62 ± 0.91 vs 1.69 ± 0.48 and 1.44 ± 0.20 g, respectively, P<0.05], and higher wet lung weight/dry lung weight ratio [18.14 (range 11.55-26.31) vs 7.80 (range 4.79-12.18), and 6.34 (range 5.92-7.04), respectively, P<0.05]. Total cell and neutrophil counts were higher in group 3 compared to groups 1 and 2 (P<0.05), as were baseline TNF-a concentrations [134 (range <10-386) vs 16 (range <10-24), and 17 pg/ml (range <10-23), respectively, P<0.05]. Serum TNF-a concentrations reached a higher level in group 3, but without statistical significance. These results suggest that mechanical ventilation with high V_T induces lung injury with inflammatory characteristics. This ventilatory strategy can affect the release of TNF-a in the lungs and can reach the systemic circulation, a finding that may have relevance for the development of a systemic inflammatory response.

Palavras-chave : Lung injury; Mechanical ventilation; Inflammation; TNF-a.