Skip to main content

Time required for gas exchange equilibration after a change of positive end-expiratory pressure in acute respiratory distress syndrome


Positive end-expiratory pressure (PEEP) is fundamental to prevent lung collapse in ARDS patients. A common method to titrate PEEP is to perform a PEEP test, recording the variation of cardiorespiratory parameters after a PEEP change [1]. The aim of this study was to evaluate the time-course changes of gas exchanges following a PEEP test.


Mechanically ventilated patients (PEEP 10 cmH2O and TV 7 ml/kg - Baseline) were randomized to two groups: in the PEEP 15 group, PEEP was increased from 10 to 15 cmH2O; while in the PEEP 5 group, PEEP was decreased from 10 to 5 cmH2O. Arterial gas analyses were performed in both groups after 5, 15, 30 and 60 minutes from the change of PEEP.


We enrolled 44 ARDS patients: 23 in the PEEP 15 group and 21 in the PEEP 5 group. At Baseline, PaO2/FiO2 (P/F) and PaCO2 were similar in both groups (P/F 169.5 ± 78.8 vs. 165.4 ± 80.6; PaCO2 45.6 ± 8.5 vs. 41.7 ± 5.0 mmHg, PEEP 15 vs. PEEP 5, respectively). In the PEEP 15 group, P/F significantly continuously increased over time. In PEEP 5, P/F significantly decreased after 5 minutes and remained stable over time. In the PEEP 15 group, PaCO2 did not change within 60 minutes after PEEP increase. When PEEP was reduced (PEEP 5) PaCO2 remained stable for the first two steps, while at 30 and 60 minutes PaCO2 was significantly higher than at Baseline (Figures 1 and 2).

Figure 1
figure 1

Two-way ANOVA RM. P < 0.05, *versus Time 0, #versus 5 minutes, °versus 15 minutes.

Figure 2
figure 2

Two-way ANOVA RM. P < 0.05, #versus 5 minutes.


Our data indicate that it is important in critically ill patients to allow sufficient time for the full effect of PEEP increase on oxygenation and to prevent excessive delay when P/F decrease occurs following the application of a lower level of PEEP.


  1. N Engl J Med. 2006, 354: 1775-1786. 10.1056/NEJMoa052052

Download references

Author information

Authors and Affiliations


Rights and permissions

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and Permissions

About this article

Cite this article

Coppola, S., Chiumello, D., Menga, F. et al. Time required for gas exchange equilibration after a change of positive end-expiratory pressure in acute respiratory distress syndrome. Crit Care 17 (Suppl 2), P113 (2013).

Download citation

  • Published:

  • DOI:


  • Respiratory Distress
  • Respiratory Distress Syndrome
  • Distress Syndrome
  • Acute Respiratory Distress Syndrome
  • Full Effect