Vent Settings

Introduction to Vent Management – Eddie Qian

Ventilator Settings:

  • FiO2 or Fraction of inspired oxygen (%)
  • PEEP or Positive End Expiratory Pressure (mmHg)
  • RR or respiratory rate (breaths per minute)
  • Vt or Tidal volume (mL) [in VC modes or PRVC]
  • Pressure Support above PEEP [in PC/PS modes]
  • Flow rate: how fast a volume is delivered; adjusting this variable changes the inspiratory to expiratory (I:E) time in volume control ventilator modes
  • Trigger: what initiates a breath; time, flow, or pressure (pt triggers are flow and pressure)
  • Cycle: when to stop delivering breath; time (pressure control modes), flow (pressure support modes), or volume (volume control modes)
  • Alarms: peak pressure, low pressure, minute ventilation, pt disconnect

 

Static Ventilator Readouts:

  • Plateau pressure (Pplat): measure with inspiratory hold (i.e. breath held at the end of inspiration and pressure measured); assesses static lung compliance
  • Auto-PEEP: measure with expiratory hold; occurs when volume of previous breath is not entirely expelled before the next breath is initiated

 

Dynamic Ventilator Readouts:

  • Measured RR: in most modes, pt may trigger breaths above set RR; if set and measured RR match, 2/2 respiratory drive (over sedated, neurologic injury) or iatrogenic over-ventilation
  • VTi / VTe: tidal volume of inspiration (VTi) and expiration (VTe); VTi should approximately equal VTe, if not then concern for air leak (e.g. cuff leak or pneumothorax) or auto-PEEP
  • Minute ventilation: calculated from VTe x RR; higher MV = more CO2 clearance
  • Peak pressure: highest pressure reached in the entire ventilator cycle

 

Critical Non-ventilator Hemodynamic Readouts:

  • SpO2: if poor waveform or discordant with PaO2, may need serial ABG
  • HR: quickest indicator of emergencies such as pneumothorax, PE, ventilator disconnection
  • Blood pressure (cuff or arterial line): positive pressure ventilation decreases preload and decreases afterload; depending on the underlying pt physiology, increases in positive pressure may be detrimental or beneficial for BP

 

Ventilator troubleshooting:

  • Peak Pressure Alarm: either a problem with the ability of the lung to stretch (compliance) or with airflow in the tubing (resistance); the inspiratory hold will remove the movement of air and give you a plateau pressure; if plateau pressure is high lung compliance is the issue, if it is normal airflow (resistance) is the issue.
    • Compliance Issues: processes filling the alveoli (ARDS, DAH, pulmonary edema), abdominal compartment syndrome, circumferential burn, kyphosis, obesity, PTX, mainstem intubation
    • Resistance Issues: bronchospasm, mucous plug, biting the tube, kink in the tubing from the endotracheal tube to the machine, water in the tubing
  • Low Minute Ventilation Alarm (this reports EXHALED minute ventilation): either your pt is apneic or there is a leak in your system and remember the system may also be in the pt; fix the leak; if they are not on a mode with a set RR, please ask for this to be switched.
    • This should also be the alarm for ventilator disconnection.
  • Refractory hypoxemia: see dedicated section below
  • At the VA, you may adjust the vents as your discretion but always inform the RT as a courtesy
  • At VUMC, do NOT adjust the ventilator, please ask RT to make adjustments
    • There are many trials going on at the VUMC MICU that you do not want to interfere with