Elsevier

Journal of Critical Care

Volume 32, April 2016, Pages 36-41
Journal of Critical Care

Outcomes/Predictors
Can lung ultrasonography predict prone positioning response in acute respiratory distress syndrome patients?

https://doi.org/10.1016/j.jcrc.2015.12.015Get rights and content

Abstract

Purpose

The purpose was to assess whether lung ultrasonography (L-US) is a useful tool in prediction of prone positioning (PP) oxygenation response in patients with acute respiratory distress syndrome (ARDS).

Methods

In a prospective study, 19 ARDS patients were included for assessment of PP oxygenation response. The latter was assessed for at least 12 hours 6 different ultrasonography windows were performed on each hemithorax before prone (H0, H2, H12 before return to supine and at H14 (2 hours after return to supine). Patients were classified into 2 groups (responders / non responders) according their oxygenation response to PP. Ultrasonography videos were blindly evaluated by 3 expert clinicians to classify lung regions as “normal”, “moderate loss of aeration,” “severe loss of aeration,” or “lung consolidation.” Oxygenation parameters were collected at H0, H2, and H14.

Results

Association of each lung region aspect to PP oxygenation response was compared between the 2 groups. The normal aspect of the anterobasal regions was significantly associated with the oxygenation response (P = .0436), with a positive predictive value equal to or near 100%.

Discussion

Our results demonstrated that a simple and short L-US examination could be a useful tool in prediction of PP oxygenation response in ARDS patients. A normal L-US pattern of both anterobasal lung regions in supine position may predict a significant Pao2/Fio2 ratio improvement.

Introduction

Once low stretch ventilation strategy is applied [1], prone positioning (PP) is an additional therapy for managing patients with severe acute respiratory distress syndrome (ARDS). Prone positioning has shown its routine feasibility [2], [3], [4] and potential oxygenation benefits, but may also induce various adverse events [5]. Up to 70% to 80% of ARDS patients experience oxygenation improvement with PP, but there are no conclusive criteria to predict oxygenation response [3].

General ultrasonography (US) is noninvasive, radiation-free, cheap, easy to use, and widely available as a bedside technique. Its use has increased in intensive care unit (ICUs) during the last decade. Ultrasonography has been validated for hemodynamic management, pleural effusions, and pneumothorax detection and central vein catheter placement [6], [7], [8], [9]. Moreover, superficial lung aspect can be visualized using lung ultrasonography (L-US).

The main objective of this preliminary prospective physiological study was to determine whether L-US patterns of aeration in specific pulmonary regions may predict PP oxygenation response in ARDS patients. We assumed that PP would be beneficial to patients with low aerated posterobasal regions and aerated anterior regions as identified using L-US.

Section snippets

Methods

Local ethics committees waived patients’ written informed consent (CHU Brest Ethics Committee and Comité de Protection des Personnes Ouest VI; 12/05/2011) given the noninvasive procedure used in this prospective physiological study.

Patients

Nineteen patients were prospectively included during a 13-month period: 12 were classified as severe and 7 as moderate ARDS patients according to the Berlin definition [10]. Initial physiological characteristics’ (H0) distribution according to oxygenation course at H2 and H14 is depicted in Table 1, Table 2. Eighteen patients remained within the same group (responders/nonresponders) between H2 and H14: 1 patient was classified as nonresponder at H2 and became responder at H14.

Most of the ARDS

Discussion

Prone positioning and the mechanism by which it can improve patient oxygenation have been investigated over the past years. Gattinoni et al described PP mechanism through a so-called sponge model. According to this model, patient’s oxygenation can be improved through inversion of gravitational forces with homogenous distribution of inflation throughout lung parenchyma. The latter depends on factors such as lung-chest wall shape matching and heart weight [20], [21]. According to Sud et al [22],

Conclusion

Despite several limitations due to the small sample of patients, this study highlighted the usefulness of easy-to-use bedside L-US in assessment of PP oxygenation response in ARDS patients. A normal L-US pattern of both left and right anterobasal regions in supine position may be useful in prediction of an early and late oxygenation improvement in PP.

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