• ARDS
• COVID-19
• awake prone positioning
• hypoxemic respiratory failure
• intubation rate
• mortality
• oxygenation

• National Natural Science Foundation of China

• Humans
• COVID-19/therapy
• Respiration, Artificial/methods
• Prone Position
• Lung
• Respiratory Distress Syndrome/therapy
• Multicenter Studies as Topic

• COVID-19
• acute respiratory distress syndrome
• end-expiratory lung volume
• nitrogen washin/washout
• oxygenation
• prone position

• Novel coronavirus disease 2019 (COVID-19)
• Viral pneumonia
• acute respiratory distress syndrome (ARDS)
• noninvasive ventilation
• prone positioning (PP)

• ARDS
• COVID-19
• SARS-CoV-2
• awake prone position
• hypoxaemic respiratory failure
• noninvasive respiratory support
• tracheal intubation

• COVID-19/therapy
• Humans
• Noninvasive Ventilation/methods
• Patient Positioning/methods
• Prone Position/physiology
• Respiratory Insufficiency/therapy
• Wakefulness/physiology

The application of prone positioning with acute hypoxemic respiratory failure (AHRF) or acute respiratory distress syndrome (ARDS) in non-intubation patients is increasing gradually, applying prone positioning for more high-flow nasal oxygen therapy (HFNC) and non-invasive ventilation (NIV) patients. This meta-analysis evaluates the efficacy and tolerance of prone positioning combined with non-invasive respiratory support in patients with AHRF or ARDS.

We searched randomized controlled trials (RCTs) (prospective or retrospective cohort studies, RCTs and case series) published in PubMed, EMBASE and the Cochrane Central Register of Controlled Trials from 1 January 2000 to 1 July 2020. We included studies that compared prone and supine positioning with non-invasive respiratory support in awake patients with AHRF or ARDS. The meta-analyses used random effects models. The methodological quality of the RCTs was evaluated using the Newcastle–Ottawa quality assessment scale.

A total of 16 studies fulfilled selection criteria and included 243 patients. The aggregated intubation rate and mortality rate were 33% [95% confidence interval (CI): 0.26–0.42, I² = 25%], 4% (95% CI: 0.01–0.07, I² = 0%), respectively, and the intolerance rate was 7% (95% CI: 0.01–0.12, I² = 5%). Prone positioning increased PaO₂/FiO₂ [mean difference (MD) = 47.89, 95% CI: 28.12–67.66; p < 0.00001, I² = 67%] and SpO₂ (MD = 4.58, 95% CI: 1.35–7.80, p = 0.005, I² = 97%), whereas it reduced respiratory rate (MD = −5.01, 95% CI: −8.49 to −1.52, p = 0.005, I² = 85%). Subgroup analyses demonstrated that the intubation rate of shorter duration prone (⩽5 h/day) and longer duration prone (>5 h/day) were 34% and 21%, respectively; and the mortality rate of shorter duration prone (⩽5 h/day) and longer duration prone (>5 h/day) were 6% and 0%, respectively. PaO₂/FiO₂ and SpO₂ were significantly improved in COVID-19 patients and non-COVID-19 patients.

Prone positioning could improve the oxygenation and reduce respiratory rate in both COVID-19 patients and non-COVID-19 patients with non-intubated AHRF or ARDS.

The reviews of this paper are available via the supplemental material section.

• acute hypoxemic respiratory failure
• acute respiratory distress syndrome
• meta-analysis
• prone positioning

The use of positive end-expiratory pressure (PEEP) and prone position (PP) is common in the management of severe acute respiratory distress syndrome patients (ARDS). We conducted this study to analyze the variation in lung volumes and PEEP-induced lung volume recruitment with the change from supine position (SP) to PP in ARDS patients.

The investigation was conducted in a multidisciplinary intensive care unit. Patients who met the clinical criteria of the Berlin definition for ARDS were included. The responsible physician set basal PEEP. To avoid hypoxemia, FiO₂ was increased to 0.8 1 h before starting the protocol. End-expiratory lung volume (EELV) and functional residual capacity (FRC) were measured using the nitrogen washout/washin technique. After the procedures in SP, the patients were turned to PP and 1 h later the same procedures were made in PP.

Twenty-three patients were included in the study, and twenty were analyzed. The change from SP to PP significantly increased FRC (from 965 ± 397 to 1140 ± 490 ml, p = 0.008) and EELV (from 1566 ± 476 to 1832 ± 719 ml, p = 0.008), but PEEP-induced lung volume recruitment did not significantly change (269 ± 186 ml in SP to 324 ± 188 ml in PP, p = 0.263). Dynamic strain at PEEP decreased with the change from SP to PP (0.38 ± 0.14 to 0.33 ± 0.13, p = 0.040).

As compared to supine, prone position increases resting lung volumes and decreases dynamic lung strain.

The online version of this article (10.1186/s13613-018-0371-0) contains supplementary material, which is available to authorized users.

• ARDS
• Lung strain
• Lung volumes
• Mechanical ventilation
• PEEP recruitment
• Prone

• Acute respiratory distress syndrome
• Mechanical ventilation
• Pathophysiology
• Prone position
• Ventilator-induced lung injury

• backrest elevation
• continuous lateral rotation
• early mobilisation
• positioning therapy
• prone position
• pulmonary disorder

• Critical Care
• Early Ambulation/methods
• Germany
• Guideline Adherence
• Humans
• Lung Diseases/prevention & control
• Patient Positioning/adverse effects
• Postoperative Complications/etiology
• Postoperative Complications/prevention & control
• Prone Position
• Rotation

• Prone positioning
• acute respiratory distress syndrome (ARDS)
• mortality

Recruitment maneuvers are often used in critical care patients with hypoxemic respiratory failure. Although continuous positive airway pressure/pressure support (CPAP/PS) ventilation is a frequently used approach, but whether lung recruitment also improves oxygenation in spontaneously breathing patients has not been investigated yet. The primary objective was to analyze the effect of recruitment maneuver on oxygenation in patients ventilated in CPAP/PS mode.

Following baseline measurements PEEP was increased by 5 cmH₂O. Recruitment maneuver was applied for 40 s with 40 cmH₂O of PS. Measurements of the difference in PaO₂/FiO₂ and airway parameters measured by the ventilator were recorded immediately after recruitment then 15 and 30 min later. Thirty patients ventilated in CPAP/PS mode with a PEEP ≥5 cmH₂O were enrolled in this prospective, observational study if their PaO₂/FiO₂ ratio was <300 mmHg or required an FiO₂ >0.5.

Following recruitment maneuver patients were considered as non-responders (NR, n = 15) if difference of PaO₂/FiO₂ <20% and responders (R, n = 15) if difference of PaO₂/FiO₂ ≥20%. In the NR-group, PaO₂/FiO₂ decreased non-significantly from baseline: median [interquartile], PaO₂/FiO₂ = 176 [120–186] vs. after recruitment: 169 [121–182] mmHg, P = 0.307 while in the R-group there was significant improvement: 139 [117–164] vs. 230 [211–323] mmHg, P = 0.01. At the same time points, dead space to tidal volume ratio (Vds/Vte) significantly increased in the NR-group Vds/Vte = 32 [27–37] vs. 36 [25–42]%, P = 0.013 but no significant change was observed in the R-group: 26 [22–34] vs. 27 [24–33]%, P = 0.386.

Recruitment maneuver improved PaO₂/FiO₂ ratio by ≥20% in 50% of patients ventilated in CPAP/PS mode.

• CPAP ventilation
• capnography
• lung compliance
• lung recruitment
• positive end-expiratory pressure

• Meta-analysis
• Metanálisis
• Posición prona
• Prone position
• Respiratory distress syndrome, adult
• Síndrome de dificultad respiratoria del adulto

Prone positioning (PP) has been reported to improve the survival of patients with severe acute respiratory distress syndrome (ARDS). However, it is uncertain whether the beneficial effects of PP are associated with positive end-expiratory pressure (PEEP) levels and long durations of PP. In this meta-analysis, we aimed to evaluate whether the effects of PP on mortality could be affected by PEEP level and PP duration and to identify which patients might benefit the most from PP.

Publications describing randomized controlled trials (RCTs) in which investigators have compared prone and supine ventilation were retrieved by searching the following electronic databases: PubMed/MEDLINE, the Cochrane Library, the Web of Science and Elsevier Science (inception to May 2013). Two investigators independently selected RCTs and assessed their quality. The data extracted from the RCTs were combined in a cumulative meta-analysis and analyzed using methods recommended by the Cochrane Collaboration.

A total of nine RCTs with an aggregate of 2,242 patients were included. All of the studies received scores of up to three points using the methods recommended by Jadad et al. One trial did not conceal allocation. This meta-analysis revealed that, compared with supine positioning, PP decreased the 28- to 30-day mortality of ARDS patients with a ratio of partial pressure of arterial oxygen/fraction of inspired oxygen ≤100 mmHg (n = 508, risk ratio (RR) = 0.71, 95 confidence interval (CI) = 0.57 to 0.89; P = 0.003). PP was shown to reduce both 60-day mortality (n = 518, RR = 0.82, 95% CI = 0.68 to 0.99; P = 0.04) and 90-day mortality (n = 516, RR = 0.57, 95% CI = 0.43 to 0.75; P < 0.0001) in ARDS patients ventilated with PEEP ≥10 cmH₂O. Moreover, PP reduced 28- to 30-day mortality when the PP duration was >12 h/day (n = 1,067, RR = 0.73, 95% CI = 0.54 to 0.99; P = 0.04).

PP reduced mortality among patients with severe ARDS and patients receiving relatively high PEEP levels. Moreover, long-term PP improved the survival of ARDS patients.

• Adult
• Breath Tests/instrumentation
• Carbon Dioxide/analysis
• Diagnosis, Computer-Assisted/instrumentation
• Diagnosis, Computer-Assisted/methods
• Equipment Design
• Equipment Failure Analysis
• Female
• Functional Residual Capacity
• Humans
• Lung Volume Measurements/instrumentation
• Male
• Reproducibility of Results
• Respiration, Artificial/instrumentation
• Sensitivity and Specificity

• Animals
• Breath Tests
• Critical Care
• Diagnostic Imaging
• Functional Residual Capacity/physiology
• Helium
• Humans
• Lung/anatomy & histology
• Lung/physiology
• Lung Volume Measurements
• Plethysmography
• Positive-Pressure Respiration
• Pulmonary Alveoli
• Ventilator Weaning

• Acute Lung Injury/mortality
• Acute Lung Injury/physiopathology
• Data Interpretation, Statistical
• Humans
• Intensive Care Units
• Prone Position/physiology
• Randomized Controlled Trials as Topic
• Respiration, Artificial/methods
• Respiratory Distress Syndrome/mortality
• Respiratory Distress Syndrome/physiopathology

• Acid-Base Imbalance/diagnosis
• Carbon Dioxide/analysis
• Critical Care/methods
• Humans
• Hypoxia/diagnosis
• Hypoxia/physiopathology
• Intensive Care Units
• Monitoring, Physiologic/instrumentation
• Monitoring, Physiologic/methods
• Oxygen Consumption/physiology
• Respiration, Artificial
• Respiratory Function Tests
• Respiratory Mechanics/physiology

• Blood Gas Analysis
• Evaluation Studies as Topic
• Humans
• Lung/physiopathology
• Lung Volume Measurements
• Positive-Pressure Respiration
• Prone Position
• Pulmonary Gas Exchange
• Respiratory Distress Syndrome/metabolism
• Respiratory Distress Syndrome/physiopathology
• Respiratory Distress Syndrome/therapy
• Respiratory Mechanics