What are the recommended ventilator modes for patients requiring mechanical ventilation?

Recommended Ventilator Modes for Mechanical Ventilation

For patients requiring mechanical ventilation, volume-cycled assist-control (AC) ventilation is the recommended initial mode, with low tidal volumes (4-8 mL/kg predicted body weight) and plateau pressures ≤30 cmH₂O to minimize ventilator-induced lung injury and mortality. 1

Initial Mode Selection

Start with volume-cycled assist-control (AC) ventilation when initiating mechanical ventilation, as this provides complete ventilatory support immediately after intubation and ensures a backup respiratory rate that prevents central apneas. 1, 2

• AC mode guarantees a set number of mandatory breaths per minute while allowing patient-triggered breaths, all delivering the same preset tidal volume 2
• This mode is particularly appropriate at the outset of mechanical ventilation for sepsis-related respiratory failure and ARDS 1
• AC prevents hypoventilation during sleep and provides superior sleep quality compared to pressure support ventilation 2

Critical Ventilator Settings (Lung-Protective Strategy)

Tidal Volume

Target 6 mL/kg predicted body weight (not actual body weight) to reduce mortality in ARDS and sepsis-induced respiratory failure. 1, 3

• Calculate predicted body weight: Men = 50 + 2.3 × (height in inches - 60); Women = 45.5 + 2.3 × (height in inches - 60) 1
• This represents a strong recommendation with high-quality evidence for ARDS patients 1
• Avoid tidal volumes of 12 mL/kg, which increase mortality 1

Plateau Pressure

Maintain plateau pressure ≤30 cmH₂O to prevent alveolar overdistension and ventilator-induced lung injury. 1, 3

• Measure plateau pressure during an inspiratory hold maneuver of 0.5-1.0 seconds 3
• Elevated plateau pressures significantly increase risk of barotrauma (pneumothorax, pneumomediastinum) 3
• This limit applies to total pressure (PEEP + driving pressure) 3

PEEP Strategy

Use higher PEEP levels (conditional recommendation) in moderate-to-severe ARDS to prevent alveolar collapse and improve oxygenation. 1

• Apply PEEP to ameliorate lung derecruitment and improve PaO₂ 1
• For moderate or severe ARDS, higher PEEP is conditionally recommended over lower PEEP 1

Oxygenation Targets

Target arterial oxygen saturation of approximately 90% (PaO₂ ~60 mmHg), or maintain SpO₂ between 88-94%. 1, 2

Alternative and Adjunctive Modes

Synchronized Intermittent Mandatory Ventilation (SIMV)

SIMV can achieve similar degrees of respiratory support as AC ventilation and may be used as an alternative. 1, 4

• SIMV provides mandatory breaths with allowance for spontaneous breaths between them 4
• Like AC, SIMV prevents central apneas due to backup respiratory rate 2, 4
• However, volume-assist control was the most common mode used (56%) in ARDS Network trials, suggesting it remains the preferred initial choice 5

Pressure Support Ventilation (PSV)

PSV is not recommended as the initial mode but may be used during weaning or for prolonged ventilation in stable patients. 2

• PSV triggers on patient effort for both inhalation and exhalation 2
• Critical caveat: Excessive PSV support can cause hyperventilation, hypocapnia, and central apneas, especially during sleep 2
• PSV lacks a backup rate, making it unsuitable for patients at risk of hypoventilation 2, 4

Pressure-Controlled Ventilation

Pressure-controlled ventilation remains uncommon (used in only 10% of patients) and offers no proven superiority over volume-cycled modes. 5

• Pressure-regulated volume-controlled ventilation can achieve similar support as AC 1

Modes to Avoid

High-frequency oscillatory ventilation (HFOV) should NOT be used routinely in moderate or severe ARDS—this is a strong recommendation against its use. 1

Ventilation Strategy for Specific Conditions

ARDS (Severe: PaO₂/FiO₂ <100)

• Use AC with low tidal volumes (6 mL/kg PBW) and plateau pressure ≤30 cmH₂O 1
• Add prone positioning for >12 hours/day (strong recommendation) 1
• Consider recruitment maneuvers (conditional recommendation) 1
• Consider neuromuscular blockade for ≤48 hours if PaO₂/FiO₂ <150 1

Post-Cardiac Arrest

Avoid hyperventilation—target normocapnia with PaCO₂ 40-45 mmHg or ETCO₂ 35-40 mmHg. 1

• Hyperventilation causes cerebral vasoconstriction and worsens brain ischemia 1
• Use low tidal volumes (6-8 mL/kg PBW) to prevent acute lung injury 1

Sepsis-Induced Respiratory Failure

Follow the same lung-protective strategy as ARDS: AC mode with tidal volume 6 mL/kg PBW and plateau pressure ≤30 cmH₂O. 1

Common Pitfalls to Avoid

• Do not use actual body weight for tidal volume calculations—always use predicted body weight 1, 3
• Do not hyperventilate patients, as this causes cerebral vasoconstriction, hemodynamic instability, and increased mortality 1
• Do not use HFOV routinely in ARDS—it does not improve outcomes 1
• Monitor for auto-PEEP in patients with obstructive lung disease, as hyperventilation without adequate expiratory time causes gas trapping and hemodynamic compromise 1, 2
• Be aware that ventilator mode terminology varies between manufacturers, which can cause confusion 2