Ch. 7: Mechanical Ventilation

Question 1

Ventilator Terminology

Answer 1

• V_t or TV-Tidal Volume.
• Dead space-Airways where no gas exchange occurs
• RR or f. Minute Ventilation (MV) generally adj. by RR.
• Permissive hypercapnea. Lower RR to allow full exhalation to avoid auto-PEEP/hyperexpansion
• FIO₂
• IFR-Inspiratory Flow Rate usually 60L/min. May need to increase in order to shorten I time and increase E time.
• PEEP-Positive End Expiratory Pressure.
• PIP-Peak inspiratory pressure
• P_plat: Plateau pressure at pause end of inspiration. Goal is usually under 30 to avoid VILI.

Question 2

Trigger

Limit

Cycle

Answer 2

• Trigger: Initiates Inspiration
• Limit: controlled during inspiration. Pressure or flow rate.
• Cycle: End of inspiration. Volume in VC. Pressure over time in PC or patient termination of inspiratory effort in Pressure Support

Question 3

Ventilator Modes

Answer 3

• CMV: Full Ventilator control. Unresponsive to pt.
• AC: Triggered by pt effort or set time for target RR
• SIMV: Pt initiated breaths above set RR are not assisted.
  
  • Can cause increased WOB.
  • Pressure support can be added to reduce.
• CPAP w PS. No backup rate. Never use if apnea risk.

Question 4

Volume vs Pressure Control

Answer 4

• Volume Control: TV set. Pressure varies with IFR, Compliance, Resistance.
  
  • Square wave Higher PIP but lower Ti
  • Decelerating reduces PIP but takes longer. Higher IFR usually used.
• Pressure Control: Pressure, RR and I:E ratio set.
  
  • TV can vary breath to breath
  • Standard I:E is 1:2.
  • Ti adjusted so Exp flow reaches zero before next breath.

Question 5

Standard Ventilator Settings

Answer 5

MODE: AC TV 6-8 ml/KG IBW RR 12 to 20

FiO2 100% PEEP 5 IFR 60

Seek PPlat < 30cm H2O

Normal minute ventilation is 100ml/kg/Min 7L in 70kg

Question 6

COPD Ventilator Settings

Answer 6

AC RR 8 TV 7ml/kg IBW

IFR 90 to 120 Use as large of an ETT as you can.