What is the best approach to manage a patient experiencing ventilator asynchrony?

Management of Ventilator Asynchrony

The best approach to managing ventilator asynchrony is to systematically adjust ventilator settings first—specifically trigger sensitivity, flow delivery, and cycling parameters—before escalating sedation, as ventilator adjustment is significantly more effective at reducing asynchrony than increasing sedation alone. 1, 2, 3

Initial Detection and Systematic Assessment

Identify the specific type of asynchrony through real-time waveform analysis by examining pressure-time and flow-time scalars at the bedside. 1, 2 Look for:

• Ineffective triggering: Patient inspiratory efforts that fail to trigger the ventilator, often visible as negative deflections in pressure waveforms without a delivered breath 2
• Delayed triggering: Lag between patient effort initiation and ventilator response 2
• Reverse triggering: Patient inspiratory effort begins after the ventilator-delivered breath has already started, creating a characteristic pattern on waveforms 1
• Premature or delayed cycling: Mismatch between when the patient wants to end inspiration and when the ventilator cycles to expiration 2

Primary Management Algorithm: Ventilator Adjustment First

Step 1: Optimize Trigger Settings

Switch from pressure triggers to flow triggers immediately, as flow sensors are more responsive and reduce overall asynchrony incidence. 1, 2 Flow sensors detect changes in machine-produced bias flow and provide better patient comfort. 2

For patients with COPD or airflow obstruction, set PEEP to 3-5 cm H₂O to offset intrinsic PEEP and reduce the effort required to trigger a breath. 1, 2 Critical pitfall: Never set PEEP higher than the patient's measured intrinsic PEEP, as this worsens air trapping and hyperinflation. 1, 2

Step 2: Adjust Respiratory Rate and Timing

For reverse triggering specifically, increase the backup respiratory rate by 1-2 breaths per minute to override the patient's intrinsic rhythm and break the entrainment pattern. 1

Adjust inspiratory time based on underlying disease:

• Obstructive disease (COPD, asthma): Use 30% IPAP time (shorter inspiratory time, I:E ratio 1:3) and prolong expiratory time to reduce dynamic hyperinflation 1, 2
• Restrictive disease: Use 40% IPAP time (longer inspiratory time, I:E ratio 1:1.5) 1

Step 3: Titrate Pressure Support or Tidal Volume

Inadequate pressure support causes increased respiratory rate and patient distress. 2 Titrate pressure support upward while monitoring patient comfort and respiratory rate—if the breathing rate falls after adjustment, the previous support was inadequate. 2

Avoid excessive pressure support, which causes hyperventilation, central apneas during sleep, and paradoxically worsens asynchrony. 2, 4

For ARDS patients, maintain low tidal volume strategy (6-8 mL/kg ideal body weight) to prevent breath-stacking from causing excessive transpulmonary pressure. 1, 2

Step 4: Consider Mode Change

Switch to Pressure Support Ventilation (PSV) for awake, spontaneously breathing patients during weaning, as it allows greater patient control over breathing pattern and improves patient-ventilator interaction. 4

Consider proportional modes (PAV or NAVA) to reduce asynchrony and improve sleep quality, though these have not demonstrated improved clinical outcomes regarding duration of mechanical ventilation or mortality. 2

Disease-Specific Ventilator Settings

COPD/Obstructive Disease

• PEEP: 3-5 cm H₂O to offset intrinsic PEEP (never exceed measured intrinsic PEEP) 1, 2
• I:E ratio: 1:3 or greater to prolong expiratory time 1, 2
• Inspiratory time: 30% IPAP time 1

ARDS

• Tidal volume: 6-8 mL/kg ideal body weight 1, 2
• PEEP: 4-8 cm H₂O for protective lung ventilation 1
• Prone positioning: Consider for at least 16 hours daily if PaO₂/FiO₂ < 150 mmHg 1

Restrictive Disease

• Inspiratory time: 40% IPAP time (I:E ratio 1:1.5) 1
• Pressure support: Adequate to achieve tidal volume with relatively low pressures (10-15 cm H₂O in neuromuscular disease) 2

When to Use Sedation (Secondary Approach)

Never increase sedation as the first-line intervention for reverse triggering, as deep sedation is a predisposing factor rather than a solution. 1 Ventilator adjustment reduces breath-stacking asynchrony significantly more effectively than increasing sedation (-99% vs -41% reduction in asynchrony index). 3

Only consider sedation adjustment after ventilator optimization fails, and avoid treating agitation with sedation before ruling out asynchrony as the underlying cause. 1, 2

Critical Monitoring After Each Adjustment

Check patient comfort, respiratory rate, and reassess waveforms immediately after every ventilator adjustment to confirm resolution of the specific asynchrony pattern. 1, 2

Monitor for loss of lung-protective ventilation parameters, particularly tidal volume exceeding 8 mL/kg ideal body weight. 1

During PSV, monitor for central apneas and adjust pressure support to maintain normocapnia, avoiding PaCO₂ <35 mmHg, especially during sleep. 4

Common Pitfalls to Avoid

• Do not ignore subtle waveform changes, as reverse triggering and other asynchronies can be easily missed without systematic analysis 1, 2
• Avoid excessive oxygen flow rates (>4 L/min), which can cause mask leak and delayed triggering 2
• Never set PEEP higher than intrinsic PEEP in obstructive disease, as this worsens air trapping rather than helping 1, 2
• Do not use sedation as first-line management, as ventilator adjustment is dramatically more effective 1, 3

Clinical Significance

High patient-ventilator asynchrony (asynchrony index ≥10%) is associated with longer duration of mechanical ventilation (mean difference 5.16 days), higher ICU mortality (OR 2.73), and higher hospital mortality (OR 1.94). 5 This underscores the importance of aggressive identification and management of asynchrony through systematic ventilator adjustment.