Exam 3 Anesthesia Ventilators (7/9/24) Flashcards
The definition of an “anesthesia ventilator” is an Automatic device designed to provide/augment these 2 things.
- Patient Ventilation
- Patient Oxygenation
What does the ventilator replace on anesthesia workstations?
Replaces the reservoir bag
What were/are some of the disadvantages to older ventilators?
- Provided only controlled mandatory ventilation (CMV)
- Couldn’t provide high enough inspiratory pressure
- Couldn’t provide PEEP
- Offered only volume control ventilation
What is the definition of barotrauma?
injury resulting from high airway pressures
What do decreases in compliance in a breathing system cause?
A decrease in tidal volume
In newer ventilators, this mode alters the volume delivered to compensate for system compliance.
Pressure controlled
The energy expended by the patient/ventilator to move gas in and out of lungs:
Work of Breathing
What is the definition of Peak Pressure?
A. Maximum pressure during the expiratory phase time
B. Maximum pressure during the inspiratory phase time
C. Minimum pressure during the expiratory phase time
D. Minimum pressure during the inspiratory phase time
B. Maximum pressure during the inspiratory phase time
In older vents, as ___ increased so did ___.
FGF
Tidal Volume
What is fresh gas compensation?
A means to prevent FGF from affecting Vt by measuring Vt and adjusting volume of gas delivered by the ventilator
Normal I:E ratio
1:2
The spill valve allows excess gases to be sent to the ____ during ___.
Scavenging system
Exhalation
This is the valve that opens to allow driving gas to exit the bellows housing:
Exhaust Valve
DURING INHALATION
What are some factors affecting ventilation?
- System Compliance
- Patient Compliance
- Leaks around tubes
True or False:
Leaks cause a decrease in tidal volume that can be compensated for by the ventilator.
FALSE:
Leaks cause a decrease in tidal volume that can’t be compensated for by the ventilator.
The Bellows Ventilators have a “Pressure-limiting mechanism” that limits _____ pressure.
What are some patient comorbidities/active issues that will cause a “High-Alarm”?
Limits Inspiratory Pressure
Things like ARDS, Pulm Edema may cause a High Alarm but we can alter the alarm settings to avoid the constant alarming
What is a good set point for the Pressure limiting mechanism on Bellows Ventilators?
10cm H2O above peak pressure with desired Vt
What squeezes gas out of the bellows, into the lungs?
How do the bellows get refilled?
Driving gas squeezes gas out of bellows into lungs
Exhalation and FGF in circuit refills bellows.
Ascending vs Descending Bellows:
Safer:
Descends on Inspiration:
Continues to descend even if disconnected:
“Standing”:
“Hanging”:
Rises on Inspiration:
Safer: Ascending
Descends on Inspiration: Ascending
Continues to descend even if disconnected: Descending
“Standing”: Ascending
“Hanging”: Descending
Rises on Inspiration: Descending
What may occur if there is improper bellows seating?
What about a hole in the bellows?
Improper seating: Inadequate ventilation
Hole: Alveolar hyperinflation/barotrauma OR the oxygen can leak out and we can also see inadequate ventilation here
A hole can be either too much or too little o2 getting to the patient
Bellows ventilators are ___ driven, whereas piston ventilators are ___ driven.
Bellows ventilators are pneumatically driven, whereas piston ventilators are mechanically driven.
True or False:
Piston Ventilators use dramatically more gas compared to bellows.
FALSE:
Piston Ventilators use dramatically LESS gas compared to bellows.
What are some problems associated with Piston ventilators?
Refills even with disconnection
Entrain room air during leaks (Dilutes oxygen/volatiles)
What is the most commonly used ventilator mode?
Volume-Controlled
Use of volume controlled ventilation can cause excessive inspiratory pressure. What can we do if this occurs?
Decrease Tidal volume if this happens = eventually decrease RR or I:E ratio if still having issues
Use of what type of ventilator mode achieves a preset pressure very quickly during inspiration?
Pressure Control
In Pressure Control, Tidal volume changes based on what?
Changes based on resistance and compliance.
With increased resistance, there will be a decreased tidal volume. Therefore, we may need to increase the PIP in order to get more volume
2 Adverse outcomes that may arise with Pressure control?
Atelectasis and Hypoventilation
How does the machine maintain Tidal volume in “Volume Guarantee Pressure-Control?
What does this help prevent?
Machine maintains Vt by adjusting PIP over several breaths
Prevents sudden Vt changes d/t compliance
What type of cases, per Dr. Kane, is Volume Guarantee Pressure-Control very beneficial for?
Laparoscopic Cases/Anything with CO2 insufflation
In assist control ventilation, how is a breath triggered?
Via a predetermined negative pressure
Assist control ventilation may cause hyperventilation. How can we fix this issue?
Switch to Intermittent mandatory ventilation:
* Mandatory ventilator breaths are set
* Additional native breaths at variable Vt
Intermittent mandatory ventilation allows for this negative effect:
What can we do if this occurs?
“Stacking”
Switch to SIMV = No “stacking”
SIMV forces an ___ delay. Which helps avoid stacking.
Inspiratory Delay between breaths.
Describe the “Pressure Support” vent setting:
- PIP and inspiratory time set
- Vt equates to native effort
- Need apnea alarm
- Used a lot for weaning
What are some ways that ventilation failure may occur?
- Disconnection from power supply
- Extremely high FGF
- Fluid in electronic circuitry
- Leaking bellows housing
How might loss of breathing system gas occur?
- Failure to occlude spill valve
- Leak in system
What are some advantages of using a ventilator?
- Allows anesthesia provider to devote energy to other tasks
- Decreases fatigue
- Produces more regular rate, rhythm, and Vt
What are some disadvantages of using a ventilator?
Trace Gas Concentrations:
50% of a gas is equal to ___ ppm.
500,000 ppm
100% = 1,000,000 ppm
Where may higher levels of Trace gases be seen?
- Pediatric anesthesia
- Dental surgeries
- Poorly ventilated PACU’s
NIOSH Recommendations for Trace anesthetic gas levels:
What are some ways our operating rooms can be contaminated with anesthetic gases?
- Poorly Fitting Masks
- Use of Uncuffed ETT’s (Peds)
- Filling Vaporizer and it spills
- Failure to turn off vaporizer
- Flushing circuit into room
- Scavenging system leak
Passive vs Active Scavenging:
Attached to Central Vacuum System:
Very Economic:
Entire volume is exhausted to atmosphere:
Attached to room ventilation system:
Must be able to provide high volume:
Attached to Central Vacuum System: Active
Very Economic: Passive
Entire volume is exhausted to atmosphere: Passive
Attached to room ventilation system: Passive
Must be able to provide high volume: Active
Things we as anesthesia providers can do to decrease the amount of trace anesthetic gases in the OR.
- Improve Mask fit
- Turn off gas flow during intubation
- 100% washout of gas at the end of the case
- Prevent spills
- Place machine close to exhaust grill as possible
What are some ways in which we could deliver hypoxic inspired gas mixtures to our patient?
If you are switching over from the pipeline to the cylinder and are unaware that the cylinder is empty, what may you cause in regards to the patients breathing?
Hypoventilation:
This can also be seen if there are leaks, disconnections, obstructions
What are some ways hypercapnia could occur?
- Iatrogenic Hypoventilation
- Absorbent failure
- Excessive dead space
- Defect coaxial system
Possible ways patients could experience an overdose of anesthetics:
- Tipped vaporizer
- Vaporizer accidentally on
- Incorrect agent in vaporizer
- Interlock system failure
- Overfilled vaporizer
A patient who is the last case of the day tells you in pre-op that they have had a horrible experience with anesthesia in the past and one of their family members suddenly died after recieving something called “sevo”. How can we ensure this patient does not have inadvertant exposure to volatiles?
- Change everything that is disposable on the anesthesia machine
- Use very high oxygen flows to flush out the machine
- Remove the vaporizers completely
- Use the auxillary flowmeters for supplemental oxygen
Disposable: Hoses, reservoir bag, Fresh gas hose, absorbent
