Asynchrony Consequences and Management

  • vent dyssynchrony occurs either with high respiratory drive or low respiratory drive
  • high respiratory drive results from too low of ventilator assistance
  • low respiratory drive results from too much ventilator assistance

High respiratory drive

Flow starvation

  • occurs when patient does not get enough air
  • can be recognized with concave indentation on pressure curve as patient pulls air in
  • management
    • increase flow rate
    • change to pressure support or pressure control so patient can adjust their own flow

Short cycling

  • occurs when patient continues to inspire during expiration
  • when strong enough can cause double triggering (second breath) or breath stacking
  • also has association with shorter inspiratory time
  • occurs often in ARDS with low TV ventilation, worse lung injury, increased respiratory drive
  • management
    • can try increase sedation, increase tidal volume, increase inspiratory time, change to PS mode

Low respiratory drive

Reverse triggering and double cycling

  • occurs more in deep sedation and decreased respiratory drive
  • ventilator triggers a muscular effort
  • can be seen with expiratory flow or decrease in inspiratory pressure in later cycle
  • can also have second breath with resulting breath stacking

Delayed cycling

  • occurs when mechanical inspiration continues after patient inspiration has stopped
  • COPD and asthma patients are at more risk, leading to shorter expiratory time

Ineffective efforts

  • occurs when patient effort does not lead to breath on the vent
  • happens more with airflow obstruction with autoPeeping => patient effort insufficient to overcome autoPeep
  • also can happen with over sedation and decreased effort
  • management
    • increase ventilator sensitivity
    • switch from pressure to flow trigger
    • give more PEEP for autoPeeping

Central apneas