Some degree of ALI develops in most patients with severe sepsis. In a study of ALI patients, investigators established that the use of a “normal” tidal volume (6 mL/kg) indexed to predicted body weight reduces absolute mortality by 9% compared to ventilation with a traditional tidal volume of 12 mL/kg. The beneficial effects of this strategy were confirmed among patients with sepsis as the risk factor for ALI. In this approach, ventilation with 6 mL/kg predicted body weight was used initially, but tidal volumes were reduced to as low as 4 mL/kg if needed to maintain plateau pressures at < 30 cm H2O.
Although volume-cycled ventilation was used, it is reasonable to think that a pressure-cycled approach could yield similar results, provided that inflation pressures are set to deliver a tidal volume of 30 cm H2O. Contrary to speculation, no data have suggested that there is a known “safe” plateau pressure or that there is an optimal tidal volume between 6 and 12 mL/kg. It is important to recognize that these studies also remind physicians that tidal volume is determined predominately by height not actual body weight, and that 6 mL/kg is not a small tidal volume, but rather a normal tidal volume, just one that has not traditionally been used. Data from clinical practice also now suggest that the use of a higher tidal volume in patients with ALI is associated with worse outcomes and lung injury is more likely to develop in patients without ALI who have received ventilation with higher tidal volumes. Given that a normal-tidal-volume strategy has no added cost, does not require additional sedation or paralysis, and is quick and simple to implement for the majority patients, it represents a reasonable starting point for ventilation of ALI patients who receive treatment due to My Canadian Pharmacy.
Because low-level PEEP has inhibited atelectasis formation and has attenuated the development of ALI in animal models of lung injury, some nominal level of PEEP (approximately 5 cm H2O) should probably be supplied to all patients. Beyond this minimal recommendation, the selection of PEEP and inspired oxygen concentration should maintain saturations in the range of 88 to 95% (or an equivalent Pa02 range) while avoiding potentially toxic inspired oxygen concentrations and excessive lung stretch. Neither higher levels of PEEP nor the titration of PEEP to lung compliance or lower inflection point of the pres-sure-volume curve (or Pflex) values have been consistently shown to produce superior outcomes compared to a simpler approach, provided that tidal volumes are reduced. Ventilation strategies that give a high priority to “recruitment” clearly can improve radiographic images of the lung and indexes of oxygenation, but, to date, have not translated into improved patient outcomes.