What is the best approach to manage patient-ventilator asynchrony in a critically ill intensive care unit (ICU) patient with potential respiratory muscle weakness and pre-existing respiratory or cardiac conditions?

Approach to Patient-Ventilator Asynchrony in the ICU

Begin by examining ventilator waveforms (pressure and flow tracings) at the bedside to identify the specific type of asynchrony, then systematically adjust ventilator settings—starting with trigger sensitivity, PEEP, and pressure support—before considering sedation or advanced modes. 1

Immediate Detection and Identification

Waveform analysis is your primary diagnostic tool and must be performed continuously to detect asynchrony patterns. 1 Look specifically for:

• Ineffective triggering: Patient inspiratory efforts visible on the flow waveform that fail to trigger a ventilator breath, often caused by intrinsic PEEP 1
• Delayed triggering: A visible lag between the start of patient effort (downward deflection in flow) and ventilator response 1
• Double triggering: Two ventilator breaths delivered in rapid succession from a single patient effort 2
• Premature cycling: The ventilator terminates inspiration before the patient's neural inspiratory time ends 3

Critical pitfall: Treating agitation with sedation first without ruling out asynchrony as the underlying cause can worsen outcomes and prolong mechanical ventilation. 1

Systematic Correction Algorithm

Step 1: Optimize Trigger Settings

• Switch from pressure triggers to flow triggers immediately—flow triggers reduce asynchrony incidence and provide better patient comfort. 1
• Flow sensors detect changes in machine-produced bias flow and are more responsive to patient effort. 1
• Adjust trigger sensitivity to the most sensitive setting that doesn't cause auto-triggering. 1

Step 2: Address Intrinsic PEEP (Auto-PEEP)

For patients with obstructive lung disease (COPD, asthma):

• Set EPAP/PEEP to 3-5 cm H₂O to offset intrinsic PEEP and reduce the effort required to trigger breaths. 1
• Never set PEEP higher than the patient's intrinsic PEEP—this worsens hyperinflation and can be harmful. 1
• Note that intrinsic PEEP in severe COPD may reach 10-15 cm H₂O, but EPAP levels >5 cm H₂O are rarely tolerated. 1
• Prolong expiratory time to reduce dynamic hyperinflation and gas-trapping. 1

Critical pitfall: Setting PEEP too high in obstructive disease worsens air trapping rather than helping. 1

Step 3: Titrate Pressure Support

• If respiratory rate is elevated (>25 breaths/min) and patient appears distressed, increase pressure support incrementally while monitoring comfort and respiratory rate. 1
• If the breathing rate falls after adjusting pressure support upward, the previous support level was inadequate. 1
• Avoid excessive pressure support—this causes hyperventilation during sleep, central apneas, and paradoxically worsens asynchrony. 1

Step 4: Adjust Ventilator Mode Based on Disease State

For obstructive lung disease (COPD, asthma):

• Prioritize prolonged expiratory time 1
• Use modest PEEP (3-5 cm H₂O) to offset intrinsic PEEP 1
• Never exceed intrinsic PEEP with applied PEEP 1

For restrictive disease (neuromuscular weakness, chest wall disorders):

• Achieve adequate tidal volume with relatively low pressures (10-15 cm H₂O) in neuromuscular disease 1
• Higher pressures may be needed in chest wall disease due to reduced compliance 1

For ARDS:

• Use low tidal volume strategy (6-8 mL/kg ideal body weight) 1, 4
• Apply protective lung ventilation with PEEP 4-8 cm H₂O 4
• Consider prone positioning for at least 16 hours per day if PaO₂/FiO₂ < 150 mmHg 4

Step 5: Consider Mode Changes for Refractory Asynchrony

• Switch to timed/assist-control mode for patients with advanced respiratory failure, neuromuscular disease, or those dependent on hypoxic respiratory drive. 1
• 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. 1, 2

Role of Sedation and Neuromuscular Blockade

• Titrate sedation according to protocol with regular drug interruption to minimize excessive sedation. 4
• For severe ARDS with persistent dyssynchrony despite ventilator adjustments, short-term neuromuscular blockade (≤48 hours) with cisatracurium may be necessary to prevent high transpulmonary pressures and breath stacking. 4
• Deep sedation alone cannot totally exclude generation of high transpulmonary pressure and can paradoxically favor certain forms of asynchrony like reverse triggering. 4
• Neuromuscular blockade should be reserved for patients with the most severe ARDS, mainly in the acute phase and during the first 48 hours of mechanical ventilation. 4
• Prolonged neuromuscular blockade increases risk of ICU-acquired weakness, especially with concomitant corticosteroids. 4

Continuous Monitoring and Reassessment

• Check patient comfort and respiratory rate immediately after any ventilator adjustment. 1
• Reassess waveforms continuously to ensure the intervention resolved the specific asynchrony type. 1
• Monitor for subtle asynchronies that may be undetectable without waveform analysis. 1

Additional Technical Considerations

• Limit oxygen flow rates to ≤4 L/min—excessive flow causes mask leak and delayed triggering, promoting asynchrony. 1
• Ensure proper mask fit in non-invasive ventilation, as poor fit causes inspiratory effort and end-inspiration to fail detection. 4
• Use barrier dressings from the outset to prevent nasal bridge ulceration during prolonged NIV. 4

Clinical Impact

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 Asynchrony is also clearly associated with ventilator-induced diaphragmatic dysfunction. 6 Therefore, systematic monitoring and correction of asynchrony is mandatory to improve outcomes in spontaneously breathing mechanically ventilated patients. 3