Lower tidal volumes better in ARDS

Daily POEMs

Published: August 2000 © 2000 John Wiley & Sons, Inc.

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Clinical question
Do lower tidal volumes improve outcomes for mechanically ventilated patients with acute respiratory distress syndrome (ARDS)?

Bottom line
Lower tidal volumes improve outcomes in patients with ARDS. See the article for the detailed protocol. (LOE = 1b)

Reference
The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000; 342: 1301-8.

Study design: Randomized controlled trial (non-blinded)

Setting: Inpatient (ICU only)

Synopsis
There is a theoretical basis to believe that the tidal volumes typically used for mechanical ventilation (10 - 15 ml / kg), higher than the usual physiologic tidal volume, may actually increase lung injury in ARDS. Patients (n = 861) at one of 10 centers in the United States who met the following criteria were recruited: intubated and receiving mechanical ventilation; an acute decrease in the ratio of partial pressure of arterial oxygen to fraction of inspired oxygen to 300 or less; bilateral infiltrates consistent with edema; and no evidence of left atrial hypertension. Patients under age 18, who were terminally ill, had serious burns, or underlying neuromuscular, sickle cell, or chronic respiratory disease were excluded. The high tidal volume group was started as 12 ml/kg of ideal body weight based on gender and height, and reduced by 1 ml/kg if necessary to maintain an end-inspiratory airway pressure of 50 cm or water or less, with a minimum of 4 ml/kg. The low tidal volume group was reduced to 6 ml/kg within 4 hours of randomization, and the pressure similarly decreased until the end-inspiratory airway pressure was 25 cm of water. There is more to the protocol, and if you plan to apply this you must read the original article. The investigators found that the rate of death at 6 months was lower in the low tidal volume group (31% vs 39.8%, p = 0.007, NNT = 12). Other outcomes such as the number of days without failure of nonpulmonary organs between days 1 and 28 and the proportion breathing without assistance at day 28 were also improved.

Mark H. Ebell, MD, MS
Professor
University of Georgia
Athens, GA

Copyright © 2000 John Wiley & Sons, Inc.