Ventilation Modes: CMV, AC, and SIMV

Introduction

• The lecture uses a ventilator to illustrate differences between three ventilation modes:
  • Continuous Mandatory Ventilation (CMV)
  • Assist Control Ventilation (AC)
  • Synchronized Intermittent Mandatory Ventilation (SIMV)

Volume Control CMV (Controlled Mandatory Ventilation)

• Definition: Ventilator controls the respiratory rate, tidal volume, and flow.
• Settings:
  • Tidal volume of 500 ml
  • Flow of 60 liters per minute
  • Respiratory rate of 10 breaths per minute
• Characteristics:
  • Breaths occur every 6 seconds (e.g., at 0, 6, 12, 18 seconds)
  • Uniform pattern because the patient is not initiating breaths
  • Vent in full control of volume and flow

Volume Control AC (Assist Control)

• Similar to CMV: Same settings (tidal volume, flow, respiratory rate)
• Characteristics:
  • Patient can trigger additional breaths above the set rate
  • Ventilator controls volume and flow of each breath
  • Breaths remain uniform regardless of the number of breaths initiated by the patient
  • Patient dictates the frequency of breaths, but not the size or flow of each breath

Volume Control SIMV (Synchronized Intermittent Mandatory Ventilation)

• Settings:
  • Similar tidal volume, flow, and respiratory rate
  • Additional settings: pressure support and slope
• Characteristics:
  • Allows spontaneous breathing between mandatory breaths
  • Mandatory breaths occur at set intervals (e.g., every 6 seconds)
  • Spontaneous breaths vary in size, indicated by different color flow on waveform
  • Includes small and large spontaneous breaths alongside mandatory breaths

Key Differences

• CMV: Patient cannot trigger breaths beyond the controlled settings, no true volume generation
• AC: Patient can trigger breaths, but ventilator controls the breath size and flow
• SIMV: Patient can breathe spontaneously between mandatory breaths, resulting in variable volumes and flows

Conclusion

• Understanding the differences in ventilation modes is crucial for respiratory therapists
• Encouragement to engage with more educational content on the topic

Additional Information

• The instructor offers additional resources and support via social media and direct contact
• Emphasis on continual learning and community engagement for respiratory therapists

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