Fluid Responsiveness in ARDS: New Evidence Highlights Context-Dependent Diagnostic Performance

Could relying on familiar fluid responsiveness tests be misleading in ARDS care? For critical care physicians, fluid management in patients with acute respiratory distress syndrome (ARDS) is a daily challenge. Recent research mapped out the strengths and pitfalls of current diagnostic approaches—raising important questions about best practices at the bedside.

Study Design: Mapping the Evidence

This scoping review, published in BMC Anesthesiology, systematically analyzed studies from 1999 to 2024 that evaluated predictors of fluid responsiveness specifically in adult ARDS populations. Researchers included only studies reporting performance metrics like sensitivity, specificity, or area under the curve (AUC). The analysis focused on dynamic indices such as pulse pressure variation (PPV), stroke volume variation (SVV), passive leg raising (PLR), end-expiratory occlusion test (EEOT), and tidal volume challenge (VTC). Special attention was paid to differences in ventilatory settings (supine vs. prone), use of extracorporeal support (VV-ECMO), and ARDS phenotype.

Main Findings: Predictors Performed Variably

PPV was the most studied predictor but showed inconsistent results in ARDS—especially for patients with low lung compliance or those in the prone position. When PPV was adjusted for respiratory mechanics (e.g., driving pressure, compliance), its accuracy improved in select cases.

SVV had moderate and variable performance. Its diagnostic value decreased further in patients on VV-ECMO support.

EEOT and VTC performed well in some settings, especially when tested in the supine position. However, their value dropped when applied in prone ventilation or non-standard validation scenarios.

Only a handful of studies examined PLR or echocardiographic indices, and no studies included spontaneously breathing patients.

Across the board, diagnostic accuracy depended heavily on individual patient mechanics, ventilatory strategy, and the method used to validate the index.

Why Context Matters: Clinical Implications

ARDS alters lung mechanics, often reducing the reliability of dynamic indices that are more robust in general ICU populations. Factors like reduced compliance, high PEEP, prone positioning, and extracorporeal support all impact cardiopulmonary interactions—making traditional fluid responsiveness markers less dependable.

Importantly, the review highlights that fluid responsiveness does not automatically mean fluid tolerance. While a patient may increase cardiac output after a fluid bolus, this could come at the cost of worsening pulmonary edema or right heart strain—key issues in ARDS.

Evidence Gaps and Future Directions

Several knowledge gaps remain:

No studies evaluated fluid responsiveness in spontaneously breathing or non-intubated ARDS patients.

Limited data exist for prone positioning and patients on VV-ECMO.

Current studies rarely stratify performance by ARDS phenotype or severity.

Markers of fluid tolerance, such as extravascular lung water, are not routinely integrated into research protocols.

Future research should prioritize individualized, physiology-based fluid management, incorporating both responsiveness and tolerance, and adapt to evolving ARDS definitions that now include less invasively supported patients.

Conclusion

Fluid responsiveness testing in ARDS is far from straightforward. The diagnostic performance of popular dynamic predictors varies widely depending on patient mechanics, ventilation modes, and context. A shift toward individualized, tolerance-focused fluid strategies may help clinicians avoid potential harms of over-resuscitation in this high-risk population.

Key points

Most fluid responsiveness predictors (like PPV and SVV) show inconsistent accuracy in ARDS, especially under low compliance or prone position.

Adjusting PPV for respiratory mechanics can improve its reliability in selected patients.

No current evidence supports the use of these predictors in spontaneously breathing ARDS patients.

Fluid tolerance—not just fluid responsiveness—should guide resuscitation decisions in ARDS.

Individualized, context-aware approaches are urgently needed to optimize fluid management in ARDS.

Citation:

Alvarado-Sánchez JI, Caicedo-Ruiz JD, Torres-Martínez MJ, Diaztagle-Fernández JJ. Fluid responsiveness in ARDS: current evidence, knowledge gaps, and future directions — a scoping review of the literature. BMC Anesthesiol. 2026. https://doi.org/10.1186/s12871-026-03910-z