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In ARDS patients, the change from supine to prone position generates a more even distribution of the gas–tissue ratios along the dependent–nondependent axis and a more homogeneous distribution of lung stress and strain. The change to prone position is generally accompanied by a marked improvement in arterial blood gases, which is mainly due to a better overall ventilation/perfusion matching. Improvement in oxygenation and reduction in mortality are the main reasons to implement prone position in patients with ARDS. The main reason explaining a decreased mortality is less overdistension in non-dependent lung regions and less cyclical opening and closing in dependent lung regions. The only absolute contraindication for implementing prone position is an unstable spinal fracture. The maneuver to change from supine to prone and vice versa requires a skilled team of 4–5 caregivers. The most frequent adverse events are pressure sores and facial edema. Recently, the use of prone position has been extended to non-intubated spontaneously breathing patients affected with COVID-19 ARDS. The effects of this intervention on outcomes are still uncertain.

Keywords: SARS-CoV-2, Prone position ventilation

The baby lung was originally defined as the fraction of lung parenchyma that, in acute respiratory distress syndrome (ARDS), still maintains normal inflation. Its size obviously depends on ARDS severity and relates to the compliance of the respiratory system. CO 2 clearance and blood oxygenation primarily occur within the baby lung. While the specific compliance suggests the intrinsic mechanical characteristics to be nearly normal, evidence from positron emission tomography suggests that at least a part of the well-aerated baby lung is inflamed. The baby lung is more a functional concept than an anatomical one; in fact, in the prone position, the baby lung “shifts” from the ventral lung regions toward the dorsal lung regions while usually increasing its size. This change is associated with better gas exchange, more homogeneously distributed trans-pulmonary forces, and a survival advantage. Positive end expiratory pressure also increases the baby lung size, both allowing better inflation of already open units and adding new pulmonary units. Viewed as surrogates of stress and strain, tidal volume and plateau pressures are better tailored to baby lung size than to ideal body weight. Although less information is available for the baby lung during spontaneous breathing efforts, the general principles regulating the safety of ventilation are also applicable under these conditions.

Care for patients with acute respiratory distress syndrome (ARDS) has changed considerably over the 50 years since its original description. Indeed, standards of care continue to evolve as does how this clinical entity is defined and how patients are grouped and treated in clinical practice. In this narrative review we discuss current standards – treatments that have a solid evidence base and are well established as targets for usual care – and also evolving standards – treatments that have promise and may become widely adopted in the future. We focus on three broad domains of ventilatory management, ventilation adjuncts, and pharmacotherapy. Current standards for ventilatory management include limitation of tidal volume and airway pressure and standard approaches to setting PEEP, while evolving standards might focus on limitation of driving pressure or mechanical power, individual titration of PEEP, and monitoring efforts during spontaneous breathing. Current standards in ventilation adjuncts include prone positioning in moderate-severe ARDS and veno-venous extracorporeal life support after prone positioning in patients with severe hypoxemia or who are difficult to ventilate. Pharmacotherapy current standards include corticosteroids for patients with ARDS due to COVID-19 and employing a conservative fluid strategy for patients not in shock; evolving standards may include steroids for ARDS not related to COVID-19, or specific biological agents being tested in appropriate sub-phenotypes of ARDS. While much progress has been made, certainly significant work remains to be done and we look forward to these future developments.

This study aimed to evaluate the short-term effect of prone positioning on oxygen saturation, arterial blood gas parameters, and respiratory rate in intensive care patients with COVID-19-induced acute respiratory distress syndrome (ARDS). This randomized experimental study used a six-measure time series design with control and intervention groups. A total of 90 intubated patients diagnosed with COVID-19 and ARDS were enrolled, with 45 patients in the experimental group and 45 in the control group. The experimental group received a 30-minute prone positioning session, while no intervention was applied to the control group. Data were collected using a Demographic Information Form and a structured form to record oxygen saturation, blood gas parameters, and respiratory rate. This study was registered at ClinicalTrials.gov (Identifier: NCT06997666; first posted on 28/05/2025). Age and gender were comparable between groups ( p  > 0.05). Patients in the experimental group demonstrated higher mean values of peripheral oxygen saturation (SpO₂), arterial oxygen saturation (SaO₂), and partial pressure of oxygen (PaO₂), along with lower PaCO₂ and respiratory rates. No significant changes were observed in sodium or lactate levels. All effects observed were immediate and short-term. No adverse events or unintended effects were reported. A single short-duration session of prone positioning resulted in immediate physiological improvements in oxygenation, ventilation parameters, and respiratory rate in patients with COVID-19-related ARDS. Further studies are needed to assess long-term clinical outcomes and sustained benefits.

Background The effects of awake prone position on the breathing pattern of hypoxemic patients need to be better understood. We conducted a crossover trial to assess the physiological effects of awake prone position in patients with acute hypoxemic respiratory failure. Methods Fifteen patients with acute hypoxemic respiratory failure and PaO 2 /FiO 2  < 200 mmHg underwent high-flow nasal oxygen for 1 h in supine position and 2 h in prone position, followed by a final 1-h supine phase. At the end of each study phase, the following parameters were measured: arterial blood gases, inspiratory effort (Δ P ES ), transpulmonary driving pressure (Δ P L ), respiratory rate and esophageal pressure simplified pressure–time product per minute (sPTP ES ) by esophageal manometry, tidal volume ( V T ), end-expiratory lung impedance (EELI), lung compliance, airway resistance, time constant, dynamic strain ( V T /EELI) and pendelluft extent through electrical impedance tomography. Results Compared to supine position, prone position increased PaO 2 /FiO 2 (median [Interquartile range] 104 mmHg [76–129] vs. 74 [69–93], p  < 0.001), reduced respiratory rate (24 breaths/min [22–26] vs. 27 [26–30], p  = 0.05) and increased Δ P ES (12 cmH 2 O [11–13] vs. 9 [8–12], p  = 0.04) with similar sPTP ES (131 [75–154] cmH 2 O s min −1 vs. 105 [81–129], p  > 0.99) and Δ P L (9 [7–11] cmH 2 O vs. 8 [5–9], p  = 0.17). Airway resistance and time constant were higher in prone vs. supine position (9 cmH 2 O s arbitrary units −3 [4–11] vs. 6 [4–9], p  = 0.05; 0.53 s [0.32–61] vs. 0.40 [0.37–0.44], p  = 0.03). Prone position increased EELI (3887 arbitrary units [3414–8547] vs. 1456 [959–2420], p  = 0.002) and promoted V T distribution towards dorsal lung regions without affecting V T size and lung compliance: this generated lower dynamic strain (0.21 [0.16–0.24] vs. 0.38 [0.30–0.49], p  = 0.004). The magnitude of pendelluft phenomenon was not different between study phases (55% [7–57] of V T in prone vs. 31% [14–55] in supine position, p  > 0.99). Conclusions Prone position improves oxygenation, increases EELI and promotes V T distribution towards dependent lung regions without affecting V T size, Δ P L , lung compliance and pendelluft magnitude. Prone position reduces respiratory rate and increases Δ P ES because of positional increases in airway resistance and prolonged expiratory time. Because high Δ P ES is the main mechanistic determinant of self-inflicted lung injury, caution may be needed in using awake prone position in patients exhibiting intense Δ P ES . Clinical trail registeration : The study was registered on clinicaltrials.gov (NCT03095300) on March 29, 2017.

PurposeSevere acute respiratory distress syndrome (ARDS) with PaO2/FiO2 < 80 mmHg is a life-threatening condition. The optimal management strategy is unclear. The aim of this meta-analysis was to compare the effects of low tidal volumes (Vt), moderate Vt, prone ventilation, and venovenous extracorporeal membrane oxygenation (VV-ECMO) on mortality in severe ARDS.MethodsWe performed a frequentist network meta-analysis of randomised controlled trials (RCTs) with participants who had severe ARDS and met eligibility criteria for VV-ECMO or had PaO2/FiO2 < 80 mmHg. We applied the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) methodology to discern the relative effect of interventions on mortality and the certainty of the evidence.ResultsTen RCTs including 812 participants with severe ARDS were eligible. VV-ECMO reduces mortality compared to low Vt (risk ratio [RR] 0.77, 95% confidence interval [CI] 0.59–0.99, moderate certainty) and compared to moderate Vt (RR 0.75, 95% CI 0.57–0.98, low certainty). Prone ventilation reduces mortality compared to moderate Vt (RR 0.78, 95% CI 0.66–0.93, high certainty) and compared to low Vt (RR 0.81, 95% CI 0.63–1.02, moderate certainty). We found no difference in the network comparison of VV-ECMO compared to prone ventilation (RR 0.95, 95% CI 0.72–1.26), but inferences were based solely on indirect comparisons with very low certainty due to very wide confidence intervals.ConclusionsIn adults with ARDS and severe hypoxia, both VV-ECMO (low to moderate certainty evidence) and prone ventilation (moderate to high certainty evidence) improve mortality relative to low and moderate Vt strategies. The impact of VV-ECMO versus prone ventilation remains uncertain.

Background Prone positioning improves survival in patients with ARDS; however, no consensus exists on how to define a positive response to this intervention. We conducted a systematic review and meta-analysis to map existing definitions of response to prone position in invasively ventilated patients with ARDS and to quantify their pooled proportion across existing body of evidence. We also evaluated the association between responsiveness to prone position and mortality. Methods We surveyed PubMed, Embase, and Cochrane Central Register of Controlled Trials databases from inception to July 2025. For the primary outcome (proportion of responders), pooled estimates were calculated using a random-effects model with logit transformation of individual study proportions. For the secondary outcome, we performed a pairwise meta-analysis to estimate pooled odds ratios for mortality. Results Oxygenation response, defined as a change of PaO 2 /FiO 2 from the supine to the prone position, was adopted as definition by 53 non-randomized studies. The pooled proportion of responders was estimated as 68% (95% C.I. 63–72%). Twenty-one studies assessed responsiveness using physiological variables other than, or in addition to, oxygenation, including carbon dioxide clearance, respiratory mechanics, or ventilation–perfusion matching. Using these alternative definitions, the pooled proportion of responders ranged from 45% to 53%. Of the 26 studies providing unadjusted mortality data in responders and non-responders, 11 (42%) reported a reduced risk of mortality in the responder cohort. A sensitivity analysis restricted to the five studies at serious risk of bias showed a reduced unadjusted risk of mortality in responders (OR 0.41, 95% CI 0.25–0.68; I² = 78%). Conclusions Definitions of responsiveness to prone positioning are highly heterogeneous across the literature, and the reported proportion of responders varies widely depending on the definition adopted. High risk of bias, residual confounding and substantial between-study heterogeneity, limit robust conclusions regarding the association between physiological responsiveness to prone positioning and survival. PROSPERO registration CRD420251104725.

To explore if the pressure-controlled ventilation (PCV) and pressure-controlled ventilation-volume guaranteed (PCV-VG) modes are superior to volume-controlled ventilation (VCV) in optimizing intraoperative respiratory mechanics in infants and young children in the prone position. A single-center prospective randomized study. Children's Hospital, Zhejiang University School of Medicine. Pediatric patients aged 1 month to 3 years undergoing elective spinal cord detethering surgery. Patients were randomly allocated to the VCV group, PCV group and PCV-VG group. The target tidal volume (VT) was 8 mL/kg and the respiratory rate (RR) was adjusted to maintain a constant end tidal CO2. The primary outcome was intraoperative peak airway pressure (Ppeak). Secondary outcomes included other respiratory and ventilation variables, gas exchange values, serum lung injury biomarkers concentration, hemodynamic parameters and postoperative respiratory complications. A total of 120 patients were included in the final analysis (40 in each group). The VCV group showed higher Ppeak at T2 (10 min after prone positioning) and T3 (30 min after prone positioning) than the PCV and PCV-VG groups (T2: P = 0.015 and P = 0.002, respectively; T3: P = 0.007 and P = 0.009, respectively). The prone-related decrease in dynamic compliance was prevented by PCV and PCV-VG ventilation modalities at T2 and T3 than by VCV (T2: P = 0.008 and P = 0.015, respectively; T3: P = 0.015 and P = 0.014, respectively). Additionally, there were no significant differences in other secondary outcomes among the three groups. In infants and young children undergoing spinal cord detethering surgery in the prone position, PCV-VG may be a better ventilation mode due to its ability to mitigate the increase in Ppeak and decrease in Cdyn while maintaining consistent VT. •Studies of ventilation strategies in infants and young children during prone position are limited.•VCV mode showed higher Ppeak and lower Cdyn than PCV-VG and PCV modes during prone position.•VCV and PCV-VG modes showed more stable tidal volume than PCV mode during prone position.

Background Acute respiratory distress syndrome (ARDS) is a heterogeneous condition with varying response to prone positioning. We aimed to identify subphenotypes of ARDS patients undergoing prone positioning using machine learning and assess their association with mortality and response to prone positioning. Methods In this retrospective observational study, we enrolled 353 mechanically ventilated ARDS patients who underwent at least one prone positioning cycle. Unsupervised machine learning was used to identify subphenotypes based on respiratory mechanics, oxygenation parameters, and demographic variables collected in supine position. The primary outcome was 28-day mortality. Secondary outcomes included response to prone positioning in terms of respiratory system compliance, driving pressure, PaO 2 /FiO 2 ratio, ventilatory ratio, and mechanical power. Results Three distinct subphenotypes were identified. Cluster 1 (22.9% of whole cohort) had a higher PaO 2 /FiO 2 ratio and lower Positive End-Expiratory Pressure (PEEP). Cluster 2 (51.3%) had a higher proportion of COVID-19 patients, lower driving pressure, higher PEEP, and higher respiratory system compliance. Cluster 3 (25.8%) had a lower pH, higher PaCO 2 , and higher ventilatory ratio. Mortality differed significantly across clusters (p = 0.03), with Cluster 3 having the highest mortality (56%). There were no significant differences in the proportions of responders to prone positioning for any of the studied parameters. Transpulmonary pressure measurements in a subcohort did not improve subphenotype characterization. Conclusions Distinct ARDS subphenotypes with varying mortality were identified in patients undergoing prone positioning; however, predicting which patients benefited from this intervention based on available data was not possible. These findings underscore the need for continued efforts in phenotyping ARDS through multimodal data to better understand the heterogeneity of this population.