Prognostic Value of CT Findings in Prone Positioning for Patients With ARDS

In patients with moderate to severe acute respiratory distress syndrome (ARDS), a greater difference in the extent of consolidation along the dependent-independent axis on computed tomography (CT) is associated with a positive oxygenation response to subsequent prone positioning, although this does not affect survival, according to a study published in BMC Pulmonary Medicine.

In patients with ARDS, oxygenation improvement and mortality reduction are the main reasons for implementing prone positioning, although caution is needed because prone positioning may potentially cause several adverse events. Being able to predict the response of prone positioning may assist in decision-making when selecting an ARDS management strategy.

Researchers sought to assess whether CT images could offer a prognostic tool for clinicians seeking to determine: 1) whether or not to use prone positioning in patients with ARDS; and 2) likelihood of survival. To accomplish this, researchers retrospectively studied patients who underwent prone positioning for moderate to severe ARDS from October 2014 to November 2020 at a medical center in Taiwan. Using a semiquantitative CT rating scale, they quantified the extent of consolidation and ground-glass opacification (GGO) in the sternal, central, and vertebral regions at 3 levels (apex, hilum, and base) of the lungs.

A prone responder was identified by a 20% increase in the ratio of arterial oxygen pressure (PaO₂) to the fraction of oxygen (FiO₂) or a 20 mmHg increase in PaO₂. The researchers found that out of 96 patients who were included in the study, 68 (70.8%) were responders. Compared with nonresponders, responders had a significantly greater median dorsal–ventral difference in CT-consolidation scores (10 vs 7, P =.046) but not in CT-GGO scores (−1 vs −1, P =.974). Although dorsal–ventral differences in neither CT-consolidation scores nor CT-GGO scores were associated with 60-day mortality, high total CT-GGO scores (≥15) were an independent factor associated with 60-day mortality (odds ratio=4.07, P =.010).

The researchers concluded, “In patients with moderate to severe ARDS, a greater difference in the extent of consolidation along the dependent-independent axis on CT scan is associated with subsequent prone positioning oxygenation response, but not clinical outcome regarding survival.” They added, “High total CT-GGO scores are independently associated with 60-day mortality.”

The investigators added: “In complex clinical cases, where weighing the pros and cons of prone positioning is needed, a large difference in the extent of consolidation along the dependent-independent axis at the lung base may give rise to a higher likelihood of a significant response, whereas patients who presented with diffuse GGO on [high special resolution CT] had a lower probability of gaining a survival benefit from prone positioning.”

Reference

Chen Y-Y, Shu‑Hung Kuo J, Ruan S-Y, et al. Prognostic value of computed tomographic findings in acute respiratory distress syndrome and the response to prone positioning. BMC Pulm Med. 2022;22(1):71. doi:10.1186/s12890-022-01864-9