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Mechanical Ventilation- AC versus SIMV
The first breath in this cycle is one initiated by the ventilator. The second breath is the patient triggered breath. There is a slight dip at the beginning of the breath, which is the patient creating a negative pressure.
The ventilator senses this and delivers another breath. The user can set what the trigger is, in litres per minute of flow for example, to make it easier or harder for the patient to trigger the breath.
The ventilator will then deliver that breath to the set volume or pressure depending on the parameters set by the user i.e. is it pressure controlled or volume controlled ventilation.
So the ventilator assists the patient by controlling the amount of volume the patient receives
SIMV- Synchronised Intermittent Mandatory Ventilation
Just as in AC mode, if the patient does not trigger a breath, the patient will receive a set volume/pressure breath, as in the first breath here.
However in SIMV when a triggered breath is initiated the patient determines the volume, which may be smaller than the non triggered breath.
So if the patient wants a lower volume during their spontaneous efforts they will receive a lower volume.
If the patient is taking good volumes during their spontaneous breaths, this may indicate that weaning might be possible.
If the spontaneous breaths are too small, then pressure support can be added to each breath to help the patient.
- Peak and Plateau Pressure
- AC versus SIMV mode
- Positive End Expiratory Pressure (PEEP)
- Increase the rate or tidal volume?
- Phases of a breath- I:E ratio and cycle time
- Ventilation screen- what do those numbers mean?
- Pressure Support
- Modes of ventilation I
- Modes of ventilation II
- Physiologic effects
- Physiologic goals
- How do I describe how my patients ventilation?
- Trigger, Limit and Cycle
- Pressure support ventilation graphs
- 6 ways to be better with Bag-Valve-Mask
- Phase Variables
- Airway Pressure Release Ventilation (APRV)
- Pressure Volume Loop
- Lung compliance in volume controlled ventilation
- Pressure/Volume/Flow graphs
- A-a gradient
- Goals and Indications
- Anatomy of the Endotracheal Tube
- Lung Compliance
- Ventilation/Perfusion V/Q matching
- Ventilator Induced Lung Injury (VILI)
- Ventilator Associated Pneumonia (VAP)
- Phase variables...again...
Guidelines for the management of tracheal intubation in critically ill adults
Having read the guidelines I made these infographics. They are FREE. Just click on the button below.
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