Anesthesia Ventilators (Exam III) Flashcards
What were the deficiencies of older ventilators?
- Couldn’t provide high enough inspiratory pressure
- No PEEP
- Offered only volume control ventilation.
What allows driving gas to exit the bellows housing?
Exhaust valve
What is fresh gas compensation?
Machine compensation meant to prevent FGF from affecting set VT.
What is the inspiratory pause time?
What is another name for this?
Inspiratory Plateau = time in which lungs are held in the inflated position.
What is the ratio for inspiration to expiration?
1:2 typically
What is inverse ratio ventilation?
When I:E is inversed so that inspiratory time is double that of expiratory time.
What is minute volume?
VT for one minute = V̇T
When is peak pressure measured?
Inspiratory phase
What ventilator valve that allows excess gas to scavenged during exhalation?
Spill valve
What is work of breathing?
Energy expended by patient/ventilator to inhale and exhale.
What are the factors that affect delivered VT?
- FGF
- Compliance
- Leaks
Decreases in compliance cause a decrease in _____.
VT
What is the driving gas?
O₂ and/or medical air
What alarms are required on a ventilator?
Low Pressure
High Pressure
What is a good set point for our pressure limiting mechanism?
10 cmH₂O above the patients average inspiratory pressure.
10 cmH₂O above peak pressure.
What allows for observation of the bellows?
Bellows Housing (clear plastic cylinder)
What are the advantages/disadvantages of an ascending bellows?
- Safer
- Descends on inspiration
- Fails to rise if disconnected
Ascending bellows will _______ on inspiration.
descend
What are the advantages/disadvantages of a descending bellows?
- Rises on inspiration
- Continues to descend (d/t gravity) even if disconnected
What would occur with a bellows if an NGT were placed in the lung?
Bellow would collapse & “clap” due to lack of air in the lung.
What factors affect deliver VT?
- FGF
- Compliance
- Leaks
What is the most commonly used ventilator mode?
Volume Control
What parameters are set during VC ventilation?
- VT
- Respiratory rate
- I:E ratio
What should a patients VT be set to?
4-6 cc/kg
Would V̇T increase or decrease with tachypnea in a patient on volume control?
Increase. ↑ RR = ↑ V̇T on VC.
What parameters are set with Pressure Control (PC) ventilation?
- PIP
- RR
- I:E ratio
What factor changes with Pressure Control ventilation?
VT
What causes changes in tidal volume with pressure control ventilation?
Resistance & compliance
________ lungs are necessary with pressure control ventilation.
Compliant
What lung ventilation mode will protect the lung from excess pressures (and thus barotrauma) ?
PC (Pressure Control)
How would one better fill the lung in pressure control mode?
- ↑ inspiratory time
- ↑ RR
This mode of ventilation prevents sudden VT changes due to compliance.
Volume guarantee Pressure Control
What’s an example of something that would cause a rapid change in compliance?
Loss of insufflation
How does Volume Guarantee Pressure Control ventilation work?
Maintains VT by adjusting PIP over several breaths
This mode of ventilation gives a set tidal volume in response to negative pressure (aka attempted breath).
Assist Control (AC) Ventilation
Which type of ventilation allows for patient initiated inspiration at variable tidal volumes?
Intermittent Mandatory Ventilation (IMV)
How do Intermittent mandatory ventilation and Assist Control ventilation differ?
Each requires a patient inspiratory effort & negative pressure.
- AC = set tidal volume
- IMV = variable tidal volumes
Which type of ventilation allows for breath “stacking”?
IMV
What is SIMV?
Spontaneous Intermittent Mandatory Ventilation
This allows for synchronization of ventilator breaths w/ patient attempted breaths.
Which parameters are set with Pressure Support?
- PIP
- Inspiratory time
Which ventilator mode necessitates an apnea alarm?
Pressure Support
Which ventilator mode would be best for weaning off a ventilator?
- Pressure Support (PS)
- SIMV
What are common causes of ventilator failure?
- Disconnection from power supply
- ↑ ↑ ↑ FGF
- Fluid in electronic circuitry
- Leak in bellows housing
What two factors could cause a loss of breathing system gas?
- Failure to occlude spill valve
- System leak
100% of a gas is ________ ppm.
1,000,000
1% of a gas is ______ ppm.
10,000
Where are higher levels of trace gas noted?
- Pediatric anesthesia
- Dental surgeries
- Poorly ventilated PACU’s
What issues are potentially associated with trace amounts of VAA’s?
- Spontaneous abortions
- Infertility
- Birth defects
- Impaired performance
- Cancer
- Liver disease
- Cardiac disease
What is a passive scavenging system?
Exhaled gasses are vented to OR atmosphere and then room ventilation system removes.
What is an active ventilation system?
- High volume 30L/min
- Lots of suction
- Attached to central vacuum system that directly removes exhaled gasses.
What are possible causes of hypercapnia associated with the anesthesia machine and ventilator?
- Hypoventilation
- Absorbent failure
- ↑ VD
- Defective Coaxial system
