What is the role of adaptive support ventilation (ASV) in critically ill adult or geriatric patients with severe respiratory failure or acute respiratory distress syndrome?

Adaptive Support Ventilation in Critically Ill Patients

Current guidelines make no recommendation for or against using adaptive support ventilation (ASV) in critically ill adults due to very low quality evidence, though recent research suggests ASV may reduce mechanical ventilation duration compared to conventional modes. 1

Guideline Position on ASV

The 2018 Critical Care Medicine guidelines explicitly state there is no recommendation regarding the use of adaptive modes of ventilation (including ASV, proportional assist ventilation, and neutrally adjusted ventilator assist) versus pressure support ventilation for improving sleep in critically ill adults. 1 This reflects:

• Only five small randomized controlled crossover trials available, evaluating outcomes deemed important but not critical 1
• Feasibility concerns as some ICUs lack ventilators or staff trained to deliver adaptive ventilation modes 1
• Very low quality of evidence overall 1

Recent Research Evidence Favoring ASV

Despite guideline neutrality, a 2025 meta-analysis of 11 studies (627 patients) demonstrated that ASV significantly reduced mechanical ventilation duration by 0.80 days and ventilator days by 1.42 days compared to SIMV. 2 Key findings include:

• Lower peak airway pressures with ASV (mean difference: -2.16 cm H₂O), suggesting better lung-protective ventilation 2
• No differences in ICU length of stay, heart rate, minute volume, blood pressure, or gas exchange parameters 2
• High heterogeneity and study quality variations limit definitive conclusions 2

A 2015 randomized controlled trial in 229 medical ICU patients found ASV shortened median mechanical ventilation duration from 92 to 67 hours and weaning duration from 80 to 2 hours compared to pressure assist/control. 3 Additionally:

• Fewer manual ventilator adjustments required with ASV (2 vs 3 settings) 3
• Higher first-attempt extubation success rates with ASV 3
• Comparable 28-day mortality and overall weaning success 3

A 2011 pilot study in a medical ICU showed 20% of ASV patients achieved extubation readiness within 1 day versus only 4% with conventional modes. 4 The median time to extubation readiness was 1 day for ASV versus 3 days for conventional ventilation. 4

ASV Mechanism and Rationale

ASV is a closed-loop ventilation mode that automatically adjusts inspiratory pressure and respiratory rate to deliver target minute ventilation with minimum work of breathing. 5, 3, 6 The system:

• Continuously measures respiratory mechanics at each breath 5, 6
• Automatically switches between pressure-controlled, SIMV-like, or pressure support-like behavior based on patient status 6
• Aims to provide safe, effective ventilation across normal lungs, restrictive, or obstructive diseases 6

When ASV May Be Considered

ASV appears most beneficial in the weaning phase of mechanical ventilation when the goal is to reduce ventilation duration and facilitate liberation from the ventilator. 4, 3 Consider ASV for:

• Medical ICU patients mechanically ventilated >24 hours on pressure support ≥15 cm H₂O 4
• Patients with FiO₂ ≤50% and PEEP ≤8 cm H₂O who are transitioning toward weaning 4
• Settings where timely recognition of extubation readiness may be delayed (e.g., limited respiratory therapist availability) 4

ASV in ARDS Management

For patients with ARDS, ASV is not specifically addressed in expert consensus guidelines, which focus on lung-protective ventilation principles regardless of mode. 1 The fundamental ARDS ventilation strategy requires:

• Low tidal volume ventilation (4-8 mL/kg predicted body weight) 1, 7, 8
• Plateau pressure <30 cm H₂O 1, 7, 8
• Target PaO₂ 70-90 mmHg or SpO₂ 92-97% 1, 7, 8
• PEEP selection based on gas exchange, hemodynamics, and lung recruitability 1

If ASV is used in ARDS patients, it must be configured to maintain these lung-protective parameters, as the mode itself does not supersede the need for strict adherence to low tidal volume ventilation. 7, 8

Critical Caveats and Pitfalls

• ASV should not replace fundamental lung-protective ventilation principles in ARDS—tidal volumes must remain 4-8 mL/kg predicted body weight regardless of mode 7, 8
• Staff training is essential before implementing ASV, as unfamiliarity with closed-loop modes may lead to inappropriate settings or delayed recognition of problems 1
• ASV does not eliminate the need for monitoring—clinicians must verify that automatically adjusted settings maintain safe plateau pressures, driving pressures, and oxygenation targets 7, 9, 8
• The evidence base remains limited with high heterogeneity, so ASV should not be considered superior to well-executed conventional ventilation strategies 2
• For severe ARDS (PaO₂/FiO₂ <100 mmHg), proven mortality-reducing interventions take priority: prone positioning for ≥12 hours daily and consideration of neuromuscular blockade 1, 7, 8

Practical Implementation Approach

If your institution has ASV capability and trained staff:

1. Initiate ASV during the weaning phase when patients are on pressure support ≥15 cm H₂O, FiO₂ ≤50%, and PEEP ≤8 cm H₂O 4
2. Start with %MinVol setting of 80-100% and allow the ventilator to automatically adjust pressure and rate 4
3. Monitor for spontaneous breathing trial readiness: frequency/tidal volume ratio <105 breaths/min/L on pressure support ≤8 cm H₂O and PEEP ≤5 cm H₂O for ≥2 hours 4
4. Verify lung-protective parameters are maintained if using ASV in ARDS: tidal volume 4-8 mL/kg, plateau pressure <30 cm H₂O, driving pressure minimized 7, 9, 8
5. Expect fewer manual ventilator adjustments compared to conventional modes, but continue regular assessment 3