Persistence of diaphragmatic contraction influences the pulmonary inflammatory response to mechanical ventilation

Because we already showed (Brégeon, F., Roch, A., Delpierre, S., Ghigo, E., Autillo-Touati, A., Kajikawa, O., Martin, T., Pugin, J., Portugal, H., Auffray, J., Jammes, Y., 2002. Conventional mechanical ventilation of healthy lungs induced pro-inflammatory cytokine gene transcription, Respir. Physiol. Neurobiol. 132, 191-203) that non-injurious mechanical ventilation (MV) elicited inflammatory signal in paralyzed rabbits having normal lungs, we examined the role of neuromuscular blockade in the pulmonary inflammatory response. In the bronchoalveolar lavage fluid (BALF), leukocyte count, MCP-1 and IL-8 cytokine concentrations (ELISA) and mRNAs (reverse transcription polymerase chain reaction, RT-PCR) were measured in paralyzed (P) or non-paralyzed (NP) rabbits ventilated for a 6-h period. Compared to the P group and despite the tidal volume was the same, we measured in the NP one a lower compliance of the respiratory system (Crs,stat), a longer inspiratory time (Ti), a negative inspiratory tracheal pressure (Ptr) wave preceding the pump-induced positive pressure wave, and a higher peak tracheal pressure. Moreover, in NP animals, gross autopsy showed negligible lung abnormalities, and marked reduction of leukocyte count and lung cytokines (P < 0.05). Thus, the absence of neuromuscular blockade decreased the pulmonary chemotactic response to MV suggesting that the total suppression of negative pressure waves elicited by the diaphragmatic (di) contractions could be involved in this lung response to positive pressure MV.