Effect of positive end-expiratory pressure application on inflammation in acute respiratory distress syndrome patients during pressure–volume curve maneuver

Introduction

There are several studies indicating that low-tidal-volume ventilation causes less damage to the alveoli than a high tidal volume [1], but this strategy may facilitate alveolar de-recruitment and deterioration of gas exchange [2]. Recruitment maneuvers may improve gas exchange, but inflating the lungs to nearly vital capacity might be harmful due to stretch stress imposed on the pulmonary parenchyma. Alveolar macrophages liberate inflammatory cytokines in response to stretch [3]. The pressure–volume (PV) curve is a physiological tool proposed for diagnostic or monitoring purposes during mechanical ventilation in acute respiratory distress syndrome (ARDS). This maneuver effect is similar to recruitment maneuver. We study the hypothesis that the systemic level of proinflammatory cytokines may be affected by a PV curve maneuver in ARDS patients, and positive end-expiratory pressure (PEEP) application may affect these levels.

Methods

This prospective, interventional clinical trial was performed in the ICU of a teaching hospital. Twenty-two consecutive mechanically ventilated patients with clinical and radiological signs of ARDS were included in the study. A single PV curve maneuver was performed by elevating the airway pressure to 40 cmH₂O for 7 seconds with (group 2) (n = 10) or without PEEP (group 1) (n = 12) application. Plasmatic concentrations of IL-6, TNFα and antioxidant capacity, arterial blood gases and respiratory changes were measured immediately before and 5 minutes, 1 hour and 5 hours after the PV curve maneuver.

Results

The PV curve maneuver caused a minor but nevertheless significant improvement of oxygenation (P = 0.015) in both groups. In addition, plasma concentrations of TNFα of both groups were similar, but the IL-6 level was higher in the group without PEEP application than in the group with PEEP after the maneuver (P = 0.000).

Conclusion

The PV curve maneuvers with or without PEEP improved oxygenation slightly. But if the PV curve maneuvers were applied with PEEP, this did not modify systemic inflammatory mediators in mechanically ventilated ARDS patients.