Cornell Mechanical Ventilation Video

Trigger Variable

What starts inspiration

Limit Variable

What determines the max volume or pressure

Cycle Variable

What switches the ventilator from inspiration to expiration

Mandatory Breath

Vent does all the WOB

Triggered, limited, and cycled by the ventilator

Assisted Breath

Vent does most of the WOB

Triggered by the patient, limited and cycled by the ventilator

Supported Breath

Supports breath with positive pressure

Triggered by the patient, limited by the ventilator, and cycled by the patient

Spontaneous Breath

Patient does all the WOB

Triggered, limited, and cycled by the patient

Volume Control

Delivered breath has a constant volume

Set tidal volume

Continuous Mandatory Ventilation

Preset breaths/minute of a preset TV

Ventilator performs all WOB

Volume Assist/Control Mode

Preset breaths/min of TV
Spontaneous respirations allowed

• Vent detects, assists with breath

WOB: negative pressure to start breath

Downside of volume assist/control is that the vent helps with all of the breaths so can get hyperventilation

Intermittent Mandatory Ventilation and Synchronized Intermittent Mandatory Ventilation

Set number of breaths of a set TV

Patient allowed to breathe spontaneously, not assisted so variable TV

IMV: mandatory breaths delivered at a set time

SIMV: synchronized to spontaneous breath

Pressure Control

Pressure is constant for every breath

Volume Control vs Pressure Control

• With volume control, ventilator will use whatever pressure is necessary to get that volume in

  • Good for still diseased lungs because it will get the volume in

  • Downside is that we can cause barotrauma

• Upside to pressure control is that the ventilator will never give excessive pressure

  • Downside is that there are variable tidal volumes so may not be giving enough volume

  • Good when we are ventilating a patient who has normal lungs, neuromuscular disease

Difference Between PEEP and CPAP

• Difference between PEEP and CPAP is that CPAP is on a patient that is spontaneously breathing

CPAP - Continuous Positive Airway Pressure

Positive pressure applied throughout the respiratory cycle in a spontaneously breathing patient

Pressure Support

Patient’s spontaneous respirations are augmented by preset inspiratory positive pressure

“Helps” breath on inspiration by applying a small amount of positive pressure, decreasing WOB

Auto-PEEP

Incomplete expiration prior to the initiation of the next breath causes progressive air trapping (hyperinflation)

This accumulation of air increases alveolar pressure at the end of expiration, which is referred to as auto-PEEP

• Usually because we haven't given the patient enough time to expire

  • RR too high

  • Patient spontaneously breathing on their own and overriding the ventilator breaths

• On a waveform will see baseline pressure continue to go up

High Frequency Oscillatory Ventilation (HFOV)

A typpe of mechanical ventilation that uses a constant distending pressure (mean airway pressure [MAP]) with pressure variations oscillating around the MAP at very high rates (up to 900 cycles per minute

This creates small tidal volumes, with constant PEEP/positive airway pressure

Decreased ventilator-induced lung injury