What is the role of PEEP in the treatment of acute respiratory distress syndrome (ARDS) when patients ventilate with lower tidal volumes?

Updated: Mar 27, 2020
  • Author: Eloise M Harman, MD; Chief Editor: Michael R Pinsky, MD, CM, Dr(HC), FCCP, FAPS, MCCM  more...
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Answer

In the ARDS Network study, patients ventilated with lower tidal volumes required higher levels of PEEP (9.4 vs 8.6 cm water) to maintain oxygen saturation at 85% or more. Some authors have speculated that the higher levels of PEEP may also have contributed to the improved survival rates. However, a subsequent ARDS Network trial of higher versus lower PEEP levels in patients with ARDS showed no benefit from higher PEEP levels in terms of either survival or duration of mechanical ventilation. [36]

The lack of efficacy of higher levels of PEEP may have been related to the fact that the recommended levels of PEEP in the ARDS Network study were based on oxygenation, and not individualized based on lung mechanics. ARDS is an inhomogeneous process and patients may have different lung injury patterns and different chest wall mechanics. Measuring esophageal pressures with an esophageal balloon catheter allows estimation of transpulmonary pressure. Basing ventilator strategy on these pressures as PEEP is titrated might allow determination of “best PEEP” levels for improving oxygenation and minimizing volutrauma and atelectasis. [37]

Using the protective ventilation strategy of lower tidal volumes, limited plateau pressure, and higher PEEP improves survival in ARDS. Amato et al, [38] through a retrospective review of more than 3500 patients with ARDS reported in nine prior studies, found that the most important ventilation variable in determining survival is delta P (plateau pressure minus PEEP). Delta P is a reflection of lung compliance and is reliable for predicting survival in patients with ARDS who are not spontaneously breathing. In these patients, lower levels of delta P improved survival. Higher levels of PEEP and lower tidal volumes did not improve survival, unless they were associated with lower levels of delta P.


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