Draft

210  Locke Vent Dyssynchrony

210.1 Summary

  • Ventilator Troubleshooting
  • Overview:
  • A warmup riddle:
  • Part 1: ”The Ventilator is Alarming”
  • Why is this so hard? 2 conflicting principles of ventilator management
  • Why is this so hard? 2 conflicting EBM principles of critical care
  • Assisted vs Control Breath
  • Modes:
  • There are things we set and variables that result from the patient’s physiology
  • “The peak pressures are high”
  • Breath holds:

210.2 Slide outline

210.2.1 Slide 1

  • Ventilator Troubleshooting
  • Brian Locke, MD
  • Pulmonary / Critical Care Fellow
  • University of Utah ### Slide 2
  • Overview:
  • You will be faced with one of two problems:
  • “The ventilator is alarming”
  • “The patient looks uncomfortable” (or, conversely, I gave sedatives to keep them comfortable).
  • Physiology review: why does this happen?
  • Schemas for how to address ventilator alarms and patient dyssynchrony ### Slide 3
  • A warmup riddle:
  • ABG is 7.15 / 75 / 50 on FiO2 1.0 and PEEP 14, RR 30, Vt 6 ml/Kg
  • What will stop you from going up on each of these indefinitely?
  • Oxygenation obviously can’t go above pure oxygen.
  • What would happen if you kept going up on PEEP? When would you stop?
  • What would happen if you kept going fast on RR?
  • What would happen if you kept going up on the Vt? ### Slide 4
  • Part 1: ”The Ventilator is Alarming”
  • What is the alarm?
  • Circuit disconnect, Breath not Delivered
  • Inspect circuit for break or kink
  • Minute ventilation low?
  • Are you on pressure support? Put on assist control-mode
  • Are you in ACPC? This is the equivalent of high pressures
  • Minute ventilation high?
  • Is this rapid shallow breathing? Go to patient looks uncomfortable
  • Large Tidal Volume?
  • Is this breath stacking? Discuss in 2nd part
  • Most common: High peak pressures pressures ### Slide 5
  • Why is this so hard? 2 conflicting principles of ventilator management
  • Lung Protective Ventilation: ARMA, 2000
  • Sedate deeply, unnaturally small breaths to protect lung ### Slide 6
  • TODO: No text extracted from this slide. ### Slide 7
  • Why is this so hard? 2 conflicting EBM principles of critical care
  • Daily sedation vacation
  • Restart at ½ dose; avoid accumulation
  • Less sedation accumulation, faster weaning and extubation ### Slide 8
  • Why is this so hard? 2 conflicting EBM principles of critical care
  • Lung Protective Vent
  • Brainstem desired Vent
  • Deeply Sedated
  • Lightly Sedated
  • Priorities shift:
  • Early in course: most inflamed lungs. Prioritize left
  • Later in course: weaning crucial. Prioritize right
  • Ventilator Alarms how to ensure Lung Protective Vent occurring
  • Patient synchrony how to do Lung Protective Vent with least sedation
  • Ideal ### Slide 9
  • Assisted vs Control Breath
  • What the patient is getting
  • Ventilator Mode Setting
  • How the ventilator is set
  • Bump to 100% FiO2 for 2 minutes
  • Stop the honking
  • End-Inspiratory Hold
  • Alarm shows up here (Yellow or Red, based on urgency) ### Slide 10
  • Modes: ### Slide 11
  • There are things we set and variables that result from the patient’s physiology
  • In AC/VC Mode:
  • We set how the breath is given: Tidal Volume, Inspiratory Time/Flow Rate
  • The stiffness & airflow resistance of the lungs determine how much pressure required to achieve set Vt
  • The resistance to airflow determines how fast the breath comes back ### Slide 12
  • “The peak pressures are high”
  • Pressure measured at the ventilator
  • Measured pressure sum of two components
  • 1: Resistance to flow (the pressure you feel blowing through a straw)
    1. Distending pressure to inflate the alveoli + chest wall (the pressure you feel blowing a balloon up)
  • Resistive pressure depends on flow rate!
  • Distending Pressure
  • Resistive Pressure
  • Pressure measured here ### Slide 13
  • Breath holds:
  • Flow 0, then the resistive component 0. Left with only the static component.
  • End-inspiratory hold measures the plateau pressure ( the pressure with the alveoli full)
  • End-expiratory hold measures the PEEP ( the pressure when the alveoli is deflated)
  • Resistive
  • Distending ### Slide 14
  • Two examples:
  • Peak 55 cmH2O.
  • Plateau 40 cmH2O
  • Why is the pressure high?
  • Plateau 15 cmH2O ### Slide 15
  • Which do you care about?
  • Volutrauma and Barotrauma result from elevated transpulmonary pressure (static pressure difference between the alveoli and the pleural pressure)
  • LTVV we want to keep the plateau less than 30 CMH2O
  • What things cause an increase in plateau pressure?
  • Distending Pressure
  • Resistive Pressure
  • Pressure measured here ### Slide 16
  • Elevated plateau pressure
  • Stiff lungs (ARDS, pneumonia, pretty much any infiltrate)
  • Water-logged lungs (worsening edema)
  • Over-distending the alveoli
  • Tidal volume is too big
  • Ventilating only a single lung (Pneumothorax, main-stem intubation)
  • External compression (effusion, chest wall, abdomen)
  • PEEP…
  • Intrinsic PEEP aka ‘auto-PEEP’, air trapping
  • Extrinsic PEEP ### Slide 17
  • PEEP increased by 4 cmH2O… how much should the plateau go up?
  • If you recruit lung: by less than 4 cmH2O
  • If you over-distend alveoli, by less than 4 cmH2O
  • If both the above don’t change, it’ll go up by 4 cmH2O
  • 0 mmHg
  • Driving Pressure ### Slide 18
  • What if peak is high, plateau is low?
  • Problems with flow
  • Bronchospasm
  • Mucus plug
  • Kink in the ventilator tubing or ETT
  • Giving breaths with very fast rate
  • What is the consequence of a high peak pressure if the plateau is low?
  • NOTHING ### Slide 19
  • Then why are the RN’s always coming to me with the peak pressure?
  • You can’t accurately measure an accurate end-inspiratory hold if the patient is making inspiratory efforts
  • If deeply sedated or paralyzed, will be accurate.
  • Distending Pressure
  • Resistive Pressure
  • Pressure measured here
  • Muscular Effort
  • P ### Slide 20
  • Expiratory hold maneuver
  • Giving breath too fast ### Slide 21
  • In sum,
  • In ACVC, Tidal Volume and Inspiratory time are set, so pressure will vary based on the patient’s lung physiology
  • Ventilator pressures (specifically, the plateau pressure) tell you about whether current ventilation is lung protective
  • Tradeoff between Lung Protection (early) vs Light Sedation (late)
  • High peak pressure will be the finding nurses and RTs notice
  • How will this change in ACPC? (answer at end)
  • Perform a breath hold (if you can) to separate causes of elevated resistance to flow (low plateau) vs high distending pressure (high plateau) ### Slide 22
  • ”The patient looks uncomfortable”
  • “Or, I had to go up on the sedation”
  • Observation (confounded) data suggests:
  • 25% of all patients have dis-synchrony
  • 50% who are the vent more than a day will.
  • They do worse. Maybe even worse mortality ### Slide 23
  • Double Triggering -> Breath Stacking
  • Two breaths are given for the patient making one respiratory effort
  • This is a problem because it doubles the distention of the lung
  • Cause: the patient’s brain stem wants a larger/longer inspiration than the vent gives.
  • Low Tidal Volume unnatural
  • Drive to breath high ### Slide 24
  • Double Triggering -> Breath Stacking
  • Treatment options:
  • Increase sedation (often preferrable if early strict low tidal volume ventilation needed)
  • Neuromuscular blockade if needed
  • Increase vent inspiratory time
  • increase tidal volume (often preferrable if later lighter sedation prioritized. ### Slide 25
  • Flow starvation -> wasted effort
  • Cause
  • Patient wants more flow than the vent gives (common on ACVC)
  • Consequence:
  • Skeletal muscle and diaphragm strain
  • Lung injury (pleural pressure negative during efforts) ### Slide 26
  • Flow starvation -> wasted effort
  • Treatment Options:
  • Increase the flow rate to 50-60, can increase up to 80.
  • This will cause peak pressure to go up
  • Switch to ramp waveform
  • Switch to ACPC ### Slide 27
  • A warmup riddle: answers
  • ABG is 7.15 / 75 / 50 on FiO2 1.0 an PEEP 14, RR 30, Vt 6 ml/Kg
  • What will stop you from going up on each of these indefinitely?
  • Oxygenation obviously can’t go above pure oxygen.
  • What would happen if you kept going up on PEEP? When would you stop?
  • Plateau is likely to increase above 30 cmH2O
  • What would happen if you kept going fast on RR?
  • AutoPEEP due to insufficient time to exhale
  • What would happen if you kept going up on the Vt?
  • What will the RNs/RTs come to you with in ACPC instead of high peak pressure?
  • “Tidal volume [or Minute Ventilation] is low”. Can still check plat / do all the same troubleshooting ### Slide 28
  • Questions?
  • brian.locke@hsc.utah.edu

210.3 Learning objectives

  • Ventilator Troubleshooting
  • Overview:
  • A warmup riddle:
  • Part 1: ”The Ventilator is Alarming”
  • Why is this so hard? 2 conflicting principles of ventilator management

210.4 Bottom line / summary

  • Ventilator Troubleshooting
  • Overview:
  • A warmup riddle:
  • Part 1: ”The Ventilator is Alarming”
  • Why is this so hard? 2 conflicting principles of ventilator management

210.5 Approach

  1. TODO: Outline the initial assessment or decision point.
  2. TODO: Outline the next diagnostic or management step.
  3. TODO: Outline follow-up or escalation criteria.

210.6 Red flags / when to escalate

  • TODO: List red flags that require urgent escalation.

210.7 Common pitfalls

  • TODO: Capture common errors or missed steps.

210.8 References

TODO: Add landmark references or guideline citations.

210.9 Slides and assets

210.10 Source materials