Ventilators Flashcards
Ventilator definition
Automatic device designed to provide/augment
Patient ventilation
Patient oxygenation
Ventilation
volume; air, pressure, oxygen
Oxygenation
oxygen
On anesthesia workstations,
Ventilator replaces ……..
The reservoir bag
Older ventilators had what features (3)
Couldn’t provide high enough inspiratory pressure
Couldn’t provide PEEP
Offered only volume control ventilation
injury resulting from high airway pressures
Barotrauma
ratio of a change in volume to a change in pressure
Compliance
valve that opens to allow driving gas to exit the bellows housing
Exhaust valve
fresh gas compensation
a means to prevent FGF from affecting Vt by measuring Vt and adjusting volume of gas delivered by the ventilator
Inspiratory pause time
time during which lungs are held inflated at a fixed volume/pressure…..inspiratory plateau
I:E ratio
ratio of the inspiratory phase time to the expiratory phase time
Inverse ratio ventilation
inspiratory phase time is longer than expiratory phase time
normal IE ratio
1:2
Minute volume
sum of all tidal volumes in one minute
maximum pressure during the inspiratory phase time
Peak pressure
Spill valve
the valve in the ventilator that allows excess gases to be sent to scavenging system during exhalation
energy expended by the patient/ventilator to move gas in and out of lungs.
Work of breathing
energy expended by the patient/ventilator to move gas in and out of lungs.
Work of breathing
Factors that affect delivered VT (3)
FGF
compliance
leaks
On older vents, as FGF increased ______
On older vents, as FGF increased so did Vt
FGF is supposed to be ______ during inspiration
excess FGF diverted during inspiration
Compliances effect on delivered VT
Decreases in compliance in breathing system causes decrease in Vt as volume is used to expand system
Newer vents alters volume delivered to compensate for system compliance (pressure controlled)
How to detect a leak
Exhaled volume is not reaching the set amount.
a decrease Vt that can’t be compensated by the ventilator
driving gas
Driving gas stays in bellows housing -> helps compress bellows
Either oxygen, air, or mix
Usual inspiratory pressure set at
A good set-point is 10cm H2O above peak pressure with desired Vt
Limits inspiratory pressure. If you set inspiratory pressures (usually preset), start at 10.
accordion-like device
Bellows assembly
clear plastic cylinder
Housing
Allows driving gas to be vented to atmosphere on exhalation
Exhaust Valve
Communicates with inside of housing
Ascending bellows
standing
Descends on inspiration
Descending bellows
(hanging)
Rises on inspiration
Exhalation and gravity cause bellow to fall
Continues to descend d/t gravity even if disconnected
Most commonly used mode
Volume control
Preset tidal volume is delivered (fixed parameter)
Volume control
Set Vt, RR, I:E ratio
Additional breaths at machine preset Vt
What can Volume control lead to? (2)
May cause excessive inspiratory pressure
Additional breaths at machine preset Vt
When is volume control not good? (5)
Trendelenburg
obese,
pregnant
lithotomy
spont vent
Ways to fix high inpiratory pressure with VC
decrease the volume-
switch to pressure control
change positions
are they paralyzed?
High VT for too long leads to…
resp alkalosis
Preset pressure is quickly achieved during inspiration (fixed parameter)
Pressure control
Pressure control sets….
Set PIP, RR and I:E ratio
VT with Pressure control
Vt changes with resistance and compliance
Maintains Vt by adjusting PIP over several breaths
Volume guarantee Pressure-Control
Prevents sudden Vt changes d/t compliance
Lost insufflation
Predetermined negative pressure triggers breath
Assist control ventilation
Breath is set Vt
Mandatory ventilator breaths are set
Additional native breaths at variable Vt
Intermittent mandatory ventilation
What mode allows stacking
Intermittent mandatory ventilation
good for weaning.
SIMV
measure to ventilator cycled breath so there is no stacking.
Synchronizes ventilatory driven breaths with spontaneous breaths
Provides backup to weaning ventilator
PIP and inspiratory time set (3)
Pressure support
Vt equates to the native effort
Need apnea alarm
What makes ventilators not work with MRI
Standard machines have variable amounts of ferromagnetic substances
Solutions to MRI and ventilators (4)
MRI compatible machines
Anesthesia machine kept outside in hallway
Machine bolted to wall
Aluminum (not steel) tanks or pipeline gas supply
considerations for Ventilation failure (4)
Disconnection from power supply
Extremely high FGF
Fluid in electronic circuitry
Leaking bellows housing
Considerations for Loss of breathing system gas (2)
Failure to occlude spill valve
Leak in system
What kind of Incorrect settings can we have (4)
Inadvertent bumping
Not adjusted for new case
Not adjusted for position/pressure changes
Ventilator turned off for xrays
Advantages of a ventilator (3)
Allows anesthesia provider to devote energy to other tasks
Decreases fatigue
Produces more regular rate, rhythm, and Vt
Disadvantages of ventilator (6)
Loss of “feel”
Older versions may not have all the desired modes
Components are hard to clean or fix
Lack user-friendliness
Noisy or too quiet
May require high-flow driving gases…expensive
Concentration of a gas far below that needed for anesthesia or detected by smell
Trace gas concentrations
How are trace gasses written
Written in PPM (parts per million)
100% of a gas is 1,000,000ppm
1% is 10,000ppm
High levels of trace gasses are seen in…..
Higher levels seen in pediatric anesthesia, dental surgeries and poorly ventilated PACU’s (expiration)
LMA cases
Passive scavenging system
Attached to room ventilation system
Air flows through room after being filtered and adjusted for humidity and temperature
Entire volume is exhausted to atmosphere
Disposal tubing from the anesthesia machine is attached to the exhaust grill and removed with room air
consider grill location
Active scavenging system
Attached to central vacuum system
Must be able to provide high volume (30L/min)
Need plenty of suction outlets and close to anesthesia machine
How to Alte work practices with effects of scavenging (5)
Mask fit
Turn off gas flow (not vaporizer) during intubation
100% wash out at end of case
Prevent liquid spills
Place anesthesia machine as close to exhaust grill as possible
How can hypoxic inspired gas mixtures develop.
Incorrect gas in the pipeline
Incorrectly installed outlets
Oxygen tubing or hoses attached to the incorrect flow meter
Incorrect cylinder attached to yoke
Incorrect cylinder…..around world O2 is green, white, blue, and black
Flow control malfunction
Leak in oxygen flow meter
How can hypoventilation on ventilator develop
Insufficient gas
Switch from pipeline to cylinder
Replace cylinder
Obstruction
Leaks
Main machine power off
Breathing system leaks
Absorbent, connectors, gas sampling
Disconnect
What can Block inspiratory/expiratory paths
Mask wrapping
Absorbent wrapping
How can hypercapnia develop on on ventilator (4)
Hypoventilation
Absorbent failure
Excessive dead space
Defect coaxial system
How to get anesthetic OD (5)
Tipped vaporizer
Vaporizer accidentally on
Incorrect agent in vaporizer
Interlock system failure
Overfilled vaporizer
How to have Inadvertent exposure to volatiles
Change breathing system hoses and bag
Change fresh gas supply hose
Change absorbent
Use very high oxygen flows to flush machine
Remove vaporizers
Use axillary flowmeter for supplemental oxygen
