Patient-Vent Asynchrony (Mod4) Flashcards
What is Asynchrony associated with?
- Increased length of mechanical ventilation
- Increased ICU and hospital length of stay
- An increased need for tracheostomy
- Increase in ICU and hospital mortality
What are clinical changes that would cause asynchrony?
- Secretions, bronchospasm, and agitation
- Fever, hypoxemia, and hemodynamic compromise
- Artificial airway problems, leaky air pathologies, body position alterations , difficult drug admin, abdominal distension
What risk does excessive lower airway secretion production have?
Increases risk of obstruction which:
- Increases peak airway pressures during volume ventilation and…
- Decrease tidal volume in pressure ventilation
Why is assisted mechanical ventilation at a higher risk of asynchrony?
More variables to control
- vent has to meet neurologic output from resp center
- Dependent on some level of effort from the patient
Why is volume ventilation more likely to cause asynchrony?
Volume vent controls volume, flow, and time. The patient determines pressure. PC only controls pressure and time.
What mode has the most control over ventialtion?
Volume a/c
In pressure support, is volume controlled?
No, only the pressure is controlled.
Why is PAV and NAVA least likely to cause asynchrony?
PAV and NAVA don’t exert any control over the patient.
- They provide a proportional assist based on patient demand
What is Flow Asynchrony?
When the flow from the vent does not match the flow demand of the patient
- Can occur in any mode of vent
- most common in volume ventilation
Volume ventilation controls flow directly, how would pressure ventilation address flow?
Inspiratory pressure rise time or pressure slope control adjusts the rate at which flow increases from baseline to peak
moderate to strong vent demands require how much peak flow?
60 L/min or greater
What role does flow have in volume ventilation?
Flow and peak flow is set, they determine the precise inspiratory time a selected tidal volume is delivered.
How is flow asynchrony corrected in volume ventilation?
By increasing peak flow and decreasing inspiratory time to match patient demand
How is flow asynchrony corrected in pressure ventilation?
Adjusting rise time
5 types of trigger asynchrony?
- Trigger delay
- Missing Triggering
- Double triggering
- Auto triggering
- Reverse triggering
What is trigger delay?
Length of time between the beginning of neuro-inspiration and activation of the ventilator is excessive
- Should not exceed 100 milliseconds to avoid patient perception of the delay and an increase in ventilatory drive
- Inappropriate set sensitivity or when auto peep is insufficient causing mistriggers
What is missed trigger asyronchy?
Patient is unable to trigger the ventilator with each inspiratory effort
What id double triggering asynchrony?
Result of the patient’s ventilatory center wanting a larger breath or a longer inspiratory time than is set on the ventilator
- A consequence is that breaths may get stacked because pt can’t exhale between breaths
What is auto triggering?
Seemingly automatic triggering of the ventilator without any patient inspiratory effort
What is Reverse triggering?
A controlled mechanical breath results in simulation of the respiratory center triggering the subsequent breath
- This form of asynchrony occurs only during controlled ventilation
- usually found with ARDS w/controlled breaths
What is cycle asynchrony?
When the vent ends the breath at a time different from when the pts respiratory center wants to end the breath
- More common in PC than VC
- Ti is either too long or short with asynchrony
What are 2 forms of cycle asynchrony?
- Asynchrony that results in an inappropriately long inspiratory time
- Asynchrony that results in an inappropriately short inspiratory time
What is mode asynchrony?
The selection of a mode of ventilation that is highly unlikely to meet a patient’s inspiratory demand
How do you correct flow asynchrony?
- Change to decelerating flow
- Increase peak flow (>60 L/min)
- Match ventilator’s inspiratory time to patient’s inspiratory time
- Ensure that the airway pressure waveform is as similar as possible to
the ideal airway pressure waveform during controlled volume ventilation - Change to a pressure-targeted mode of ventilation
