Tidal changes on CT and progression of ARDS

Area of Science:

• Pulmonary Medicine
• Radiology
• Critical Care

Background:

• Accurate prediction of outcomes in acute respiratory distress syndrome (ARDS) is challenging for patient management and clinical trial design.
• Current methods for assessing lung injury severity and predicting prognosis in ARDS are limited.

Purpose of the Study:

• To develop and validate a novel radiological metric derived from inspiratory-expiratory CT scans to quantify injurious inflation in ARDS.
• To assess the metric's ability to predict lung injury progression and patient outcomes in experimental models and human ARDS patients.

Main Methods:

• Utilized a rat acid aspiration model to induce a spectrum of lung injury, performing paired inspiratory-expiratory CT scans.
• Analyzed superimposed CT scans to track voxels and identify regions of unstable lung inflation.
• Applied the developed metric to CT scans from nine ARDS patients during their first intensive care unit week.

Main Results:

• In experimental studies, unstable lung inflation regions correlated significantly with subsequent injury progression (R=0.77) and impaired compliance (R=0.67).
• In ARDS patients, a threshold of >28% unstable lung inflation predicted mortality, while oxygenation and lung mechanics did not segregate survivors from non-survivors.
• A distinct fraction of tissue with unstable inflation (>28%) was identified as a predictor of mortality in ARDS patients.

Conclusions:

• Superimposed inspiratory-expiratory CT scans show potential for predicting lung injury progression and patient outcomes in ARDS.
• This radiological metric could improve clinical trial recruitment and enable individualized patient management strategies.
• Further validation is needed, but this technique offers a promising non-invasive tool for ARDS prognostication.