Highlights
- The PROVID randomized clinical trial demonstrates a 93.8% posterior probability that awake prone positioning (APP) reduces the composite risk of intubation and death in COVID-19 patients.
- Optimal efficacy is associated with a target duration of at least 6 hours per day, though adherence remains a significant clinical challenge.
- APP improves oxygenation through enhanced ventilation-perfusion matching and more homogeneous distribution of pleural pressure, potentially preventing self-inflicted lung injury (P-SILI).
- Integration of Bayesian statistical models in recent trials provides a more nuanced understanding of therapeutic benefit compared to traditional frequentist approaches.
Background
Since the early stages of the COVID-19 pandemic, the management of acute hypoxemic respiratory failure (AHRF) has evolved rapidly. While prone positioning has been a cornerstone of treatment for moderate-to-severe acute respiratory distress syndrome (ARDS) in intubated patients for over a decade—based on pivotal trials like PROSEVA—its application in nonintubated, spontaneously breathing patients (awake prone positioning or APP) was initially experimental. The rationale for APP is based on the physiological benefits observed in mechanical ventilation: improved oxygenation, reduced shunting, and a decrease in the ventral-to-dorsal pleural pressure gradient, which leads to more uniform lung recruitment.
Despite early observational studies suggesting benefit, randomized controlled trials (RCTs) have yielded inconsistent results. Some studies reported significant reductions in intubation rates, while others, like the COVI-PRONE trial, showed no significant difference. This lack of consensus created a clinical need for high-quality, multicenter RCTs to clarify the efficacy and optimal “dose” of APP. The PROVID trial (Harrois et al., 2025) addresses these gaps using a robust Bayesian framework to assess the impact of APP on clinical outcomes in a diverse population across France and Mexico.
Key Content
The PROVID Trial: Study Design and Population
The PROVID trial was a multicenter, randomized clinical trial conducted at 20 hospitals in France and one in Mexico. It enrolled 445 adult patients with COVID-19-related AHRF who were not intubated and required at least 3 L/min of oxygen flow. Patients were randomized 1:1 to either APP (offered for at least 6 hours per day) or standard care. The primary outcome was a composite of endotracheal intubation or death within 28 days of randomization.
The baseline characteristics reflected a high-acuity population, with a median SpO2/FiO2 ratio of approximately 150-155. Notably, the trial utilized a Bayesian approach, which allows for the calculation of the probability of a treatment effect given the observed data, providing a more intuitive clinical interpretation than traditional p-values.
Clinical Efficacy and Bayesian Interpretation
The results of the PROVID trial provide strong support for the use of APP. Using a noninformative prior distribution, the study found a 93.8% posterior probability that APP decreased the risk of intubation or death compared to standard care. The mean odds ratio (OR) was 0.74 (95% credible interval [CrI], 0.48-1.09). While the credible interval crossed 1.0 (a common occurrence in Bayesian analyses of moderately sized trials), the high posterior probability indicates a robust likelihood of clinical benefit.
Secondary outcomes further supported the intervention’s utility. Patients in the APP group experienced an average of 1.28 more days alive outside the ICU and 1.55 more days alive outside the hospital compared to the standard care group. Although these differences had wide credible intervals, the direction of effect consistently favored APP.
Evolution of Evidence: APP across the Pandemic
To contextualize the PROVID trial, it is necessary to examine the chronological progression of APP evidence:
- Early 2020 (Observational Phase): Numerous small cohorts suggested that APP could rapidly improve oxygenation (PaO2/FiO2 ratio) in COVID-19 patients, leading to widespread but unstandardized adoption.
- 2021 (The Meta-Trial Era): The Awake Prone Positioning Meta-Trial Group (Ehrmann et al., 2021) published a landmark study combining data from six RCTs (1,126 patients). They found that APP reduced the risk of treatment failure (intubation or death) in patients receiving high-flow nasal cannula (HFNC), with a relative risk of 0.86.
- 2022 (Divergent Results): The COVI-PRONE trial (Alhazzani et al., 2022) found no significant reduction in intubation in patients with COVID-19 AHRF. This was attributed to shorter durations of prone positioning (median 5 hours) and potentially different patient selection.
- 2025 (Refinement with PROVID): The PROVID trial reinforces the benefit of a 6-hour minimum target and demonstrates that the benefit extends to patients on lower levels of oxygen support (≥3 L/min), not just those on HFNC or CPAP.
Physiological and Mechanistic Insights
The efficacy of APP in COVID-19 is largely attributed to the “squashing effect” and the redistribution of lung perfusion. In the supine position, the weight of the heart and the abdominal contents compress the posterior lung segments, which are often the most affected by COVID-19 pneumonia. Moving to a prone position relieves this compression and creates a more negative pleural pressure in the dorsal regions, promoting alveolar recruitment. Furthermore, because pulmonary blood flow remains relatively constant and directed toward the dorsal regions due to gravity and vascular architecture, prone positioning improves the matching of ventilation to perfusion (V/Q matching), thereby reducing the intrapulmonary shunt.
Another critical mechanism is the reduction of Patient-Self Inflicted Lung Injury (P-SILI). High inspiratory efforts in hypoxemic patients can generate large transpulmonary pressure swings, leading to lung strain and edema. By improving oxygenation and lung mechanics, APP may decrease the respiratory drive and the risk of P-SILI, potentially preventing the transition from noninvasive to invasive mechanical ventilation.
Expert Commentary
The PROVID trial is a significant addition to the literature, particularly for its use of Bayesian statistics which align more closely with clinical decision-making. However, several nuances must be considered. First, adherence to the 6-hour duration is a known bottleneck. While the trial “offered” 6 hours, the actual achieved duration in real-world settings often fluctuates due to patient discomfort, anxiety, or musculoskeletal pain. Clinicians should prioritize patient education and the use of specialized pillows or support systems to improve tolerance.
Furthermore, the trial included patients requiring as little as 3 L/min of oxygen. This suggests that the window for initiating APP is broader than previously thought. Rather than waiting for severe respiratory distress or the initiation of HFNC, early application of APP in the ward setting may prevent clinical deterioration. However, there is a “sweet spot”; patients who are already profoundly unstable may not benefit from APP and should not have their intubation delayed if they meet failure criteria.
One controversy remains: the “rebound” effect. Some patients show dramatic improvement while prone but desaturate immediately upon returning to a supine position. The PROVID trial’s focus on 28-day outcomes (intubation/death) helps move the conversation beyond transient physiological markers toward meaningful patient-centered outcomes.
Conclusion
The PROVID trial provides high-level evidence that awake prone positioning for at least 6 hours a day is a safe and effective strategy for reducing the need for intubation and the risk of death in patients with COVID-19-related hypoxemic respiratory failure. These results support the routine integration of APP into the standard of care for nonintubated COVID-19 patients across both ward and ICU settings. Future research should focus on optimizing adherence through behavioral interventions and determining whether these benefits extend to non-COVID-19 causes of acute respiratory failure, such as bacterial pneumonia or non-viral ARDS.
References
- Harrois A, et al. Awake Prone Positioning in Patients With COVID-19 Respiratory Failure: A Randomized Clinical Trial. JAMA Netw Open. 2025;8(12):e2548201. PMID: 41370078.
- Ehrmann S, et al. Awake prone positioning for COVID-19 acute hypoxaemic respiratory failure: a randomised, multicentre, open-label meta-trial. Lancet Respir Med. 2021;9(12):1387-1395. PMID: 34425070.
- Alhazzani W, et al. Effect of Awake Prone Positioning on Endotracheal Intubation in Patients With COVID-19 and Acute Respiratory Failure: A Randomized Clinical Trial. JAMA. 2022;327(21):2104-2113. PMID: 35569803.
- Guerin C, et al. Prone positioning in severe acute respiratory distress syndrome. N Engl J Med. 2013;368(23):2159-2168. PMID: 23688302.
