Prone Position Protocol for ARDS
For critically ill adults with severe ARDS (PaO₂/FiO₂ <150 mmHg) not improving with conventional ventilation, implement prone positioning for at least 16-17 hours daily, starting within 48 hours of intubation, while maintaining lung-protective ventilation with tidal volumes of 6 mL/kg predicted body weight. 1, 2
Patient Selection Criteria
Initiate prone positioning when ALL of the following are met:
- PaO₂/FiO₂ ratio <150 mmHg despite optimization 2, 1
- FiO₂ ≥0.6 1
- PEEP ≥5 cm H₂O 1
- Tidal volume ~6 mL/kg predicted body weight already implemented 1
- Within 48 hours of mechanical ventilation initiation 3, 4
The mortality benefit is most pronounced in severe ARDS (PaO₂/FiO₂ <150 mmHg), with meta-analyses showing risk ratios of 0.74-0.77 for mortality reduction. 1, 5 Patients with moderate ARDS (PaO₂/FiO₂ 100-300 mmHg) do not demonstrate the same survival advantage. 1
Pre-Positioning Preparation
Before turning the patient:
- Optimize volume status (ongoing vasopressor therapy is NOT a contraindication) 1
- Ensure hemodynamic monitoring is in place 1
- Verify all lines, tubes, and drains are secured 6
- Assemble adequate staff (typically 4-5 people) 6
Duration and Timing Protocol
Apply prone positioning for 16-20 hours per day: 1, 4
- Target minimum duration: 16 hours daily 1
- Optimal duration from trials: 17-20 hours daily 4
- The mortality benefit only occurs with prone duration >12 hours per day (RR 0.74; 95% CI 0.56-0.99) 5
Earlier trials using only 7-8 hours daily showed no mortality benefit, making prolonged duration critical. 4, 5
Ventilator Management During Prone Positioning
Maintain strict lung-protective ventilation:
- Tidal volume: 4-8 mL/kg predicted body weight (target ≤6 mL/kg) 1, 3
- Plateau pressure: <30 cm H₂O 1, 2
- PEEP: Maintain or increase as tolerated 1
- The limitation of tidal volume is essential for mortality benefit from prone positioning 1, 3
PEEP and prone positioning have additive effects on improving oxygenation. 3
Monitoring Response
Assess oxygenation 8-12 hours after the first prone session: 1
- Responders typically show PaO₂/FiO₂ improvement >15% 7
- Early responders (within 11.8 days of ARDS onset) have better outcomes than late responders (32.8 days) 7
- Continue daily prone positioning until improvement persists in supine position 1
Discontinuation Criteria
Stop prone positioning when ALL of the following are met 4 hours after returning to supine: 1, 3
Terminate therapy after 2 unsuccessful prone attempts (no oxygenation improvement). 1, 3
Relative Contraindications (Proceed with Caution, NOT Absolute)
The following are NOT automatic exclusions: 1
- Recent abdominal surgery 1
- Increased intracranial pressure (ICP rises significantly but requires individual risk-benefit assessment) 3
- Spinal instability 1
- Hemodynamically significant arrhythmias 1
- Shock requiring vasopressors 1
- Obesity (NOT a contraindication; may have greater oxygenation improvement) 1, 3
Expected Complications and Management
Common complications with increased frequency: 1
- Endotracheal tube obstruction (RR 1.76; 95% CI 1.24-2.50) 3, 5
- Pressure ulcers (RR 1.22; 95% CI 1.06-1.41) 3, 5
- Chest tube dislodgement 1
- Transient hypotension (monitor MAP closely) 3
- Intra-abdominal pressure increases from 12±4 to 14±5 mmHg 3
Importantly, cardiac arrests are actually REDUCED with prone positioning compared to supine. 1
Critical Pitfalls to Avoid
- Do not use prone positioning for <12 hours daily – no mortality benefit demonstrated 5
- Do not delay implementation – early application (within 48 hours) shows better outcomes 4, 7
- Do not abandon lung-protective ventilation – tidal volume limitation is necessary for mortality benefit 1, 3
- Do not exclude obese patients – obesity is not a contraindication 1
- Do not perform in hypovolemic patients – optimize volume status first 1