Impact of mechanical ventilation and fluid load on pulmonary glycosaminoglycans.

The combined effect of mechanical ventilation and fluid load on pulmonary glycasaminoglycans (GAGS) was studied in anaesthetized rats ((BW 290 +/- 21.8 (SE)g) mechanically ventilated for 4h: (a) at low (similar to 7.5 ml kg(-1)) or high (similar to 23 ml kg(-1)) tidal volume (V-T) and zero alveolar pressure; (b) at low or high V-T at 5 cmH(2)O positive end-expiratory pressure (PEEP); (c) with or without 7 ml kg(-1) h(-1) intravenous infusion of Phosphate Buffer Solution (PBS). Compared to spontaneous breathing, GAGs extractability decreased by 52.1 +/- 1.5% and 42.2 +/- 1 7.3% in not-infused lungs mechanically ventilated at low V-T or at high V-T and PEEP, respectively. In contrast, in infused lungs, GAGs extractability increased by 56.1 +/- 4.0% in spontaneous ventilation and PEEP and up to 81.1% in all mechanically ventilated lungs, except at low V-T without PEEP. In the absence of an inflammatory process, these results suggest that PEEP was protective at low but not at high V-T when alveolar structures experience exceedingly high stresses. When combined to mechanical ventilation, fluid load might exacerbate edema development and lung injury. (C) 2012 Elsevier B.V. All rights reserved.