Should we worry about tidal volume when plateau pressure is low?

Some clinicians may feel that tidal volume isn't really an issue when plateau pressure is at a safe level (< 30 cm H2O).  In a paper by Hager et al. published in 2005 in the AJRCCM journal data from the ARDSNet study was seperated into quartiles of plateau pressure.  It showed that higher plateau pressures had higher mortality, even with 6 ml/kg.  

Patient's with low AND high tidal volume that had plateau pressures in the 1st quartile all had plateau pressures < 30 cm H2O (99 and 100 patients respectively).  

The absolute risk reduction (ARR) was determined and showed an ARR of 9.4% would be achieved by decreasing tidal volume to 6 ml/kg from 12 ml/kg.

So does tidal volume matter when plateau pressures are within safe limits?  Yes.