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Internal Medicine

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The following is a screenshot of a mechanical ventilation mode. The top graph represents pressure over time. The middle graph is the flow over the time and the bottom graph is the volume over time.

Please examine this graphs carefully, and let's answer the following question:

What is this mode of mechanical ventilation?

  • 0%Pressure support ventilation (PSV)

  • 0%Assist/control mode of ventilation (A/C)

  • 0%Synchronized Intermittent Mandatory Ventilation (SIMV)

Now examine the third delivered breath and answer the following questions:

Who started the breath?

  • 0%Patient (Pressure triggered)

  • 0%Ventilator (time triggered)

What did the ventilator do (the target)?

  • 0%Delivered 380 mL tidal volume

  • 0%Delivered a pressure around 35 cm H2O

How was the inspiration ended (cycle)?

  • 0%By time

  • 0%By flow

  • 0%By volume


Thank you for your answers

This is assist control mode of ventilation. AC ventilation is a volume-cycled mode of ventilation. It works by setting a fixed tidal volume (VT) that the ventilator will deliver at set intervals of time or when the patient initiates a breath. If you notice in the settings, the ventilator is set to deliver 380 ml of air every 3.3 seconds (rate of 18 per minute). The third breath started earlier than 3.3 second and there was a negative deflection in the pressure first indicating that it is pressure triggered and not time triggered. Once the machine is triggered, it did deliver the tidal volume of 380 mL and ended the inspiration (cycle) after the volume was delivered.

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