MECHANICAL VENTILATION (INVASIVE)
Three characteristics of mechanical ventilation to guide you through the thought
process
How is lung inflation initiated?
At a fixed rate independent of patient effort (a.k.a. control)
Controlled mandatory ventilation
. Used in heavily sedated or paralyzed patients.
Triggered by patient’s inspiratory effort (a.k.a. assist)
Synchronized ventilation
Patient-triggered ventilation
. Used in awake patients
How is gas flow controlled during lung inflation?
Pressure (pressure controlled,
pressure-limited ventilation)
Tidal volume (volume-controlled
ventilation
Controls inflation pressure Controls delivered volume
Cycles when set time or flow is reached Cycles when set volume is delivered
Volume depends on compliance Pressure rises passively
How is the inflation terminated?
A set inflation time has elapsed (time cycled)
Inflation flow has decelerated to a certain percent of peak flow (flow-cycled)
A set tidal volume has been delivered (volume-cycled)