Monday, March 29, 2010

Is low tidal volume ventilation beneficial for patients who do NOT have ARDS/ALI?

It is well known that low tidal volume ventilation is beneficial in patients with ARDS/ALI. The pathophysiologic rationale, that by avoiding over distension of alveoli low tidal volume ventilation mitigates lung injury and is associated with decreased cytokine production, is appealing for ventilated patients without ARDS/ALI. Up to now, for these latter patients, although RTC evidence was lacking, several papers suggested a beneficial effect.

This retrospective cohort study showed that for each ml (ml/kg predicted body weight?) above the ARDSnet standard of 6 ml/kg PBW the odds ratio for development of ALI increased by 1.3.

This study noted a similar effect.

In this study higher plateau pressures and tidal volumes (but not tidal volumes per unit predicted body weight!?) were risk factors. This combination of findings, which translates into taller individuals being at higher risk for ARDS, is an anomaly and not reproduced in other studies.

Now, just out, is a RCT of conventional vs low tidal volume ventilation for patients who do not have ALI or ARDS:

The trial was stopped prematurely for safety reasons because development of lung injury was higher in the conventional tidal volume group as compared to the lower tidal volume group (13.5% vs. 2.6%, P = 0.01). Univariate analysis showed statistical relations between baseline lung injury score, randomization group, level of positive end-expiratory pressure (PEEP), number of transfused blood products, presence of a risk factor for ALI and baseline IL-6 lavage fluid levels and development of lung injury. Multivariate analysis revealed randomization group and level of PEEP as independent predictors of the development of lung injury.

Mechanical ventilation with conventional tidal volumes is associated with sustained cytokine production as measured in plasma. Our data suggest mechanical ventilation with conventional tidal volumes contributes to development of lung injury in patients without ALI at onset of mechanical ventilation.

Higher sedation needs and more difficulty in maintaining oxygenation, cited as barriers to the evidence based implementation of low tidal volume ventilation in patients with ARDS, were not noted in the low tidal volume group in this study.

This is a very important paper which stands an excellent chance of making my top 10 list next December!

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