Figures
- Figure 1.
A patient with acute respiratory distress syndrome receiving mechanical ventilation in the intensive care unit while in the prone position.
- Figure 2.
a) The distribution of normally aerated (white circles), poorly aerated (grey circles), non-aerated (black rectangle) and consolidated (green rectangle) lung areas during acute respiratory distress syndrome while in the supine position during end-inspiration and end-expiration. b) Barotrauma (alveolar rupture with air leaks) and volutrauma (overdistension in the normally aerated lung areas). c) Atelectrauma, i.e. shear stress in the poorly aerated lung areas close to the consolidated non-recruitable lung areas. Biotrauma (biochemical and biological response) results from volutrauma and/or atelectrauma with activation of pro-inflammatory mediators within the lungs and distant end organs. The red circle represents the heart.
- Figure 3.
Homogenisation of the distribution of lung aeration as a result of moving from a) the supine to b) the prone position during acute respiratory distress syndrome. The red circle represents the heart. White circles: normally aerated lung areas; grey circles: poorly aerated lung areas; black rectangle: non-aerated lung areas; green rectangle: consolidated lung areas.
Tables
- Table 1. Characteristics of the five largest randomised controlled trials testing the role of prone positioning in patient survival
First author [ref.] Gattinoni [31] Guérin [32] Mancebo [33] Taccone [34] Guérin [2] Patients n Supine position 152 378 60 174 229 Prone position 152 413 76 168 237 Patients with ARDS % Supine position 93.3 28 100 100 100 Prone position 94.7 33.9 100 100 100 PaO2/FIO2 at inclusion mmHg 127 150 147 113 100 Tidal volume at inclusion mL·kg−1 10.3 MBW 8 MBW 8.4 PBW 8 PBW 6.1 PBW PEEP at inclusion cmH2O 10 8 12 10 10 Prone position session duration# h 7 8 17 18 17 Mortality % Supine position 25 31.5 58 32.8 32.8 Prone position 21.1 32.4 43 31 16 ARDS: acute respiratory distress syndrome; PaO2: arterial oxygen tension; FIO2: inspiratory oxygen fraction; PEEP: positive end-expiratory pressure; MBW: measured body weight; PBW: predicted body weight. #: average hours per session.
- Table 2. Limitations in randomised controlled trials
First author [ref.] Gattinoni [31] Guérin [32] Mancebo [33] Taccone [34] Guérin [2] Year of trial 2001 2004 2006 2009 2013 Protective lung ventilation No No No Yes Yes Long prone sessions No No Yes Yes Yes Target population ALI/ARDS Hypoxaemic acute respiratory failure ARDS ARDS ARDS with severity criteria Crossover allowed Yes Yes Yes No (rescue) No (rescue) Rate of crossover Not reported 81 (21.4%) out of 378 5 (8.1%) out of 62 20 (11.5%) out of 174 17 (7.4%) out of 229 ALI: acute lung injury; ARDS: acute respiratory distress syndrome.
- Table 3. Key features in the PROSEVA trial on prone positioning in severe acute respiratory distress syndrome (ARDS) patients
1. ARDS criteria confirmed after 12–24 h 2. ARDS with severity criteria: PaO2/FIO2 <150 mmHg with FIO2 ≥0.6 + PEEP ≥5 cmH2O + VT 6 ml·kg−1 predicted body weight 3. Several noninclusion criteria 4. Strict lung protective mechanical ventilation (in both groups) 5. First prone position session started within 1 h after randomisation 6. Prone sessions of at least 16 h consecutively 7. Predetermined stopping criteria of prone position 8. Crossover not allowed except as a lifesaving procedure in the supine group 9. Neuromuscular blockade in both groups 10. Centres with expertise in prone positioning for many years PROSEVA: Proning Severe ARDS Patients; PaO2: arterial oxygen tension; FIO2: inspiratory oxygen fraction; PEEP: positive end-expiratory pressure; VT: tidal volume.
- Table 4. Characteristics of the PSII and PROSEVA randomised controlled trials on prone positioning in acute respiratory disease syndrome patients
PSII [34] PROSEVA [2] Centres n 25 27 Support Rotoprone in 20 centres Standard bed Patients n Supine position 168 229 Prone position 174 237 Inclusion criteria PaO2/FIO2 ≤200 mmHg + PEEP 5–10 cmH2O PaO2/FIO2 <150 mmHg + PEEP ≥5 cmH2O + FIO2 ≥0.60 Stratification of randomisation Yes No Stabilisation period No Yes Stopping prone criteria Resolution of ARF Improvement in oxygenation (PaO2/FIO2 >150 mmHg + PEEP <10 cmH2O + FIO2 <0.60) Target tidal volume mL·kg−1 8 PBW 6 PBW PEEP management Local PEEP/FIO2 table PEEP/FIO2 table used in the ARMA trial Target oxygenation PaO2 70–90 mmHg PaO2 55–80 mmHg Target plasma pH 7.30–7.45 7.20–7.45 SAPS II 41±15 46±16 SOFA score 6.8±3.9 10.0±3.3 PaO2/FIO2 at inclusion mmHg 113±39 104±25 PEEP at inclusion cmH2O 10±3 10±4 Tidal volume at inclusion mL·kg−1 8.0±1.7 PBW 6.1±0.6 PBW Pplat at inclusion cmH2O Not available 24±5 Average prone session duration h 18±4 17±4 Time in prone# % 50 73 Average prone position sessions per patient in the prone position group 8±6 4±4 Data are presented as mean±sd, unless otherwise stated. PSII: Prone Supine II: PROSEVA: Prone Severe ARDS Patients; PaO2: arterial oxygen tension; FIO2: inspiratory oxygen fraction; PEEP: positive end-expiratory pressure; ARF: acute respiratory failures; SAPS: Simplified Acute Physiology Score; SOFA: Sequential Organ Function Assessment; Pplat: plateau pressure; PBW: predicted body weight. #: time spent in the prone position between the start of the first session and the end of the last session.
