What are the different waveforms on Belivista (mechanical ventilator) for tracheostomy patients?

Waveform Monitoring on Bellavista for Tracheostomy Patients

Waveform capnography is essential for all tracheostomy patients on mechanical ventilation to monitor airway patency and should be continuously displayed on the Bellavista ventilator to prevent mortality from tube displacement or blockage. 1

Key Waveforms for Tracheostomy Monitoring

1. Capnography Waveform

• Normal appearance: Rectangular shape with rapid upstroke, plateau, and rapid downstroke
• Clinical significance: Most critical waveform for tracheostomy patients
• Abnormal patterns to watch for:
  • Absent waveform: Indicates complete tube displacement or obstruction
  • Dampened waveform: Suggests partial obstruction or leak
  • Gradual upsloping plateau: May indicate bronchospasm or secretions

2. Pressure Waveform

• Normal appearance: Smooth rise during inspiration, plateau if inspiratory pause set, rapid fall during expiration
• Abnormal patterns:
  • Increasing peak pressures: May indicate tube obstruction, secretions, or patient-ventilator dyssynchrony
  • Pressure oscillations: Often indicate patient coughing or fighting the ventilator
  • Inadequate pressure rise: May suggest leak around tracheostomy tube or circuit disconnect 2

3. Flow Waveform

• Normal patterns:
  • Square wave: Constant flow during volume-controlled ventilation
  • Descending ramp: Decelerating flow pattern (preferred for most patients)
  • Sinusoidal: During pressure-controlled modes
• Abnormal signs:
  • Flow not returning to zero at end-expiration: Indicates air trapping/auto-PEEP
  • Notching or irregularities: Suggest patient-ventilator dyssynchrony
  • Inadequate expiratory flow: May indicate tube narrowing or obstruction 2

4. Volume Waveform

• Normal appearance: Steadily increasing during inspiration, returning to baseline during expiration
• Abnormal patterns:
  • Failure to return to baseline: Indicates circuit leak (common around tracheostomy cuff)
  • Reduced tidal volume: May suggest tube obstruction or displacement 1

Critical "Red Flag" Waveform Changes

The British Journal of Anaesthesia identifies these critical waveform changes requiring immediate action:

1. Absence or change of capnograph waveform
2. Absence or change of chest wall movement with ventilation
3. Increasing airway pressure
4. Reducing tidal volume
5. Obvious air leak
6. Vocalization with a cuffed tube in place and inflated 1

Specialized Waveform Considerations for Tracheostomy Patients

Work of Breathing Assessment

• Tracheostomy tubes can significantly increase work of breathing, especially with high minute ventilation
• Pressure-time product waveform analysis can help identify excessive work of breathing
• Consider automatic tube compensation (ATC) mode to reduce work of breathing in spontaneously breathing patients 3

Pressure-Volume Loops

• Useful for optimizing PEEP and identifying optimal pressure ranges
• Can help detect changes in lung compliance
• Helpful in identifying circuit leaks (common in tracheostomy patients) 2

Flow-Volume Loops

• Critical for detecting airway secretions (common in tracheostomy patients)
• Help identify changes in airway resistance
• Useful for detecting leaks around tracheostomy tube cuff 2

Emergency Response to Abnormal Waveforms

If abnormal waveforms suggest tube obstruction or displacement:

1. Remove any attachments to tracheostomy tube (speaking valves, caps, humidifiers)
2. Remove inner cannula if present and replace with clean one
3. Attempt to pass suction catheter to assess patency
4. Apply high-flow oxygen to both face and tracheostomy
5. Use waveform capnography to confirm correct placement and ventilation 1

Best Practices for Waveform Monitoring

1. Ensure continuous waveform capnography for all ventilated tracheostomy patients
2. Display multiple waveforms simultaneously (pressure, flow, volume, and capnography)
3. Set appropriate alarm parameters based on individual patient baseline
4. Train all staff in waveform interpretation specific to tracheostomy patients
5. Use bedhead signs with key information about the tracheostomy and normal parameters 4

Common Pitfalls in Waveform Interpretation

• Failure to recognize the significance of absent capnography waveform
• Misinterpreting patient-ventilator dyssynchrony as agitation
• Not identifying auto-PEEP on flow waveforms
• Overlooking small but significant changes in waveform patterns
• Attributing waveform changes to ventilator issues when they represent patient deterioration 1

Remember that 50% of airway-related deaths in critical care are associated with tracheostomy displacement, and proper waveform monitoring and interpretation can prevent more than 80% of such deaths 1.