How is ventilator-associated dyssynchrony managed?

Management of Ventilator-Associated Dyssynchrony

Ventilator dyssynchrony should be considered in all agitated patients and managed through informed adjustment of ventilator settings, with particular attention to flow rate, trigger sensitivity, and patient-specific respiratory mechanics. 1

Types and Recognition of Ventilator Dyssynchrony

Patient-ventilator dyssynchrony occurs when there is a mismatch between the patient's respiratory drive and ventilator assistance. Common types include:

• Trigger dyssynchrony: Delayed triggering, auto-triggering, ineffective triggering
• Flow dyssynchrony: Inadequate flow delivery to meet patient demands
• Cycle dyssynchrony: Mismatch between patient's and ventilator's inspiratory times
• Expiratory dyssynchrony: Auto-PEEP and dynamic hyperinflation

Detection of dyssynchrony requires careful examination of ventilator waveforms, with the most sensitive method being simultaneous recordings of diaphragm electrical activity and esophageal pressure changes 1.

Management Algorithm for Ventilator Dyssynchrony

Step 1: Identify and Address Technical Issues

• Check for ventilator leaks or malfunction
• Verify endotracheal tube position and patency
• Eliminate tube obstruction (mucous plugs, kinks)
• Evaluate for auto-PEEP
• Rule out pneumothorax 1

Step 2: Optimize Ventilator Settings

For Trigger Dyssynchrony:

• Use flow triggers rather than pressure triggers to reduce asynchrony 1
• Adjust trigger sensitivity to optimize patient effort without auto-triggering

For Flow Dyssynchrony:

• Increase inspiratory flow rate (80-100 L/min for adults) 1
• Consider pressure-limited modes which provide variable flow based on patient demand 2

For Cycle Dyssynchrony:

• Adjust inspiratory time to match patient's neural timing
• Set appropriate inspiratory to expiratory ratios (1:4 or 1:5 for obstructive conditions) 1

For Auto-PEEP/Expiratory Dyssynchrony:

• Use slower respiratory rates with smaller tidal volumes (6-8 mL/kg)
• Provide longer expiratory times
• Set PEEP appropriately but avoid setting PEEP greater than intrinsic PEEP in obstructive conditions 1

Step 3: Optimize Sedation

• Titrate sedation to improve ventilator synchrony without oversedation
• Consider using propofol or benzodiazepines with inactive metabolites
• Add short-acting synthetic opioids if needed 1
• Target specific (higher) levels of alertness when appropriate 1
• Consider sedation breaks to evaluate respiratory status, but monitor closely 1

Step 4: Consider Advanced Modes and Techniques

• For persistent dyssynchrony despite optimization, consider:
  • Proportional assist ventilation
  • Neurally adjusted ventilatory assist (NAVA)
  • Pressure support ventilation with adjustable rise time and cycling criteria 1

Step 5: Last Resort Measures

• For severe dyssynchrony causing patient distress or compromising ventilation:
  • Consider neuromuscular blocking agents if dyssynchrony persists despite adequate sedation 1
  • In rare circumstances where aggressive treatment fails to provide adequate gas exchange, consider extracorporeal membrane oxygenation (ECMO) 1

Special Considerations

For Obstructive Conditions (COPD, Asthma):

• Use smaller tidal volumes (6-8 mL/kg)
• Allow for longer expiratory times (I:E ratio 1:4 or 1:5)
• Consider permissive hypercapnia to reduce barotrauma risk
• Monitor for and address auto-PEEP 1

For Restrictive Conditions:

• PEEP may assist in lung recruitment and improve compliance
• Monitor for hypoxemia and adjust PEEP accordingly 1

Monitoring and Reassessment

• Regularly review ventilator settings as patient condition changes 1
• Monitor patient comfort and respiratory rate to assess adequacy of support
• Examine pressure/flow waveforms to detect subtle forms of dyssynchrony
• Consider arterial blood gases to evaluate ventilation effectiveness

Common Pitfalls and Caveats

• Inadequate flow delivery: Insufficient flow is a common cause of dyssynchrony and patient discomfort 2
• Over-sedation: Can prolong mechanical ventilation and ICU length of stay 1
• Ignoring auto-PEEP: Can cause significant hemodynamic compromise and worsen dyssynchrony 1
• Failure to recognize dyssynchrony: Healthcare staff often miss dyssynchrony events when only observing waveforms 3
• Delayed intervention: High indices of dyssynchrony may increase duration of mechanical ventilation 3

By systematically addressing ventilator dyssynchrony through optimized settings and appropriate sedation, clinicians can improve patient comfort, potentially reduce duration of mechanical ventilation, and possibly improve outcomes 1, 3.