Use of chest sonography to estimate alveolar recruitment in general anesthesia

Introduction

Chest sonography evaluates extravascular lung water as the number of ultrasound lung comets (ULC). The goal of this study was to assess the potential role of chest sonography to detect lung reaeration after alveolar recruitment maneuvers (RM) using the PaO₂/FiO₂ ratio as reference parameter.

Methods

Chest sonography and arterial blood gas (ABG) analysis were independently performed in eight anesthetized and mechanically ventilated patients after abdominal surgery, before RM (achieved with positive end-expiratory pressure at 35 cmH₂O for 30 s) and 5 and 60 minutes later. A total of 11 anterior and lateral chest regions were studied. For each chest region, lung patterns were scored as: 0 = normal, 1 = B lines ≥ 7 mm, 2 = B lines <7 mm, 3 = white lung, 4 = alveolar consolidation. A global ULC score for each patient was calculated adding the score of the 11 chest regions. Using the PaO₂/FiO₂ ratio as reference parameter, we calculated the sensitivity, specificity and positive predictive value of the lung ultrasound. The baseline ULC score was compared with the basal PaO₂/FiO₂ ratio, and furthermore the variation of eco score was compared with the variation of the PaO₂/FiO₂ ratio.

Results

Chest sonography shows a sensitivity of 50–100%, a specificity of 75% and a positive predictive value of 67–88%. A linear correlation between the PaO₂/FiO₂ ratio and eco score was found (Figures 1 and 2).

Figure 1

Figure 2

Conclusion

Chest sonography is a promising, simple and bedside tool to estimate the efficacy of alveolar recruitment maneuvers.