Recumbency tends to accentuate the measured plateau pressure that corresponds to a given tidal volume/PEEP combination.
Interestingly, the plateau pressure (and the tidal compliance calculated from it) may not accurately reflect either lung compression or lung stretch, and is insensitive to the tidal recruitment and de-recruitment cycles that occur with every breath as the building airway pressure pushes the pleural fluid aside.
VILI is not a simple function of either tidal volume or plateau pressure.
Moreover, at these elevated frequencies, mean airway pressure would rise due to gas trapping, forcing plateau pressure to rise past the 30 cmH2O criterion, as well.
The characteristics of the individual breathing cycle--tidal volume, plateau pressure
and PEEP--are of unquestioned clinical importance and currently occupy center stage in the ventilation of acute respiratory failure.
extreme obesity or ascites) might make it prudent to accept a plateau pressure considerably higher than the upper recommended value of -30 cmH2O if the alternative is failing to meet pressing physiological demands--e.
Unless the clinician has eliminated patient effort, (s)he cannot feel entirely comfortable about a plateau pressure in the 20s.
Peak and plateau pressures
were also decreased after each RM.
We do know that poorly chosen ventilatory patterns--those involving high tidal volumes, high plateau pressures
and low levels of PEEP--exacerbate injury.