Exam 3 Anesthesia Ventilators [7/9/24] Flashcards
1
Q
Define ventilator.
A
- An automatic device that will provide/augment:
- Patient ventilation
- Patient oxygenation
S2
2
Q
On the anesthesia workstation, ventilators essentially replace what component?
A
- The green reservoir bag
S2
3
Q
What ventilation mode was available from old ventilator models?
A
- Only controlled mandatory ventilation [CMV]
- Only offered volume-controlled ventilation
- No PEEP
- Couldn’t provide high enough inspiratory pressure (PIP)
S3
4
Q
Define barotrauma
A
- Injury resulting from high airway pressures
S4
5
Q
What is compliance?
A
- Ratio of a change in volume to a change in pressure
- C= ΔV/ΔP
S4
6
Q
Decrease in compliance in the breathing system causes what?
A
- Decrease in compliance in breathing system causes decrease in Vt as volume is used expand to system (volume controlled)
S4
7
Q
How do newer vents compensate for system compliance?
A
- New vents will alter the volume delivered to compensate for system compliance (pressure control)
S4
8
Q
What is work of breathing?
A
The energy that the patient/ventilator expends to move gas in and out of the lungs.
S4
9
Q
What is Peak Pressure (PIP) ?
A
- The maximum pressure during the inspiratory phase time
S4
10
Q
Define FGF.
A
- Gas that is coming into the machine that picks up vapor.
S5
11
Q
- On older vents, as FGF increases, what happens to tidal volume?
- In newer vents, if there is excess FGF, what happens?
A
- Old Vents: as FGF increases, the tidal volume increases
- New Vents: have excess FGF divereted during inspiration
S5
12
Q
What is Fresh Gas Compensation?
A
- This is a way to prevent FGF from affecting tidal volume by measuring tidal volume and adjusting the volume of gas delivered by the ventilator
S5
13
Q
What is inspiratory pause time?
A
The time during which lungs are held inflated at a fixed volume and pressure. (Inspiratory plateau)
can increase the pause time to keep the alveoli open
- Google: Inspiratory plateau is measured during the inspiratory pause.
S5
14
Q
What is the I:E ratio?
A
- Ratio of the inspiratory phase time to the expiratory phase time
S6
15
Q
- Normal I:E Ratio
- Give an example of when youd want a longer I:E ratio.
A
- 1:2 (1 sec inspiration : 2 second expiration)
- We spend more time expiring
- slow exhalation = keeps pressure in chest for longer period of time —>increases intrathoracic pressure (decreases venous return and CO)
-obese, CO2 inflation, trendelenburg = increase inspiratory pressure more which we want to limit.
-Change I:E to 1:1.5 or 1:1 to limit gas in the chest
S6-lecture
16
Q
- What is an inverse ratio ventilation?
- what is an example?
A
- Inspiratory phase time is longer than the expiratory phase time
- 2:1 (2 sec inspiration : 1 sec expiration)
S6
17
Q
The sum of all tidal volumes in one minute
A
- Minute volume
S6
18
Q
What is the spill valve?
A
- The valve in the ventilator that allows excess gases to be sent to scavenging system during exhalation (Outside of the vent bellows)
S7
19
Q
What is the exhaust valve?
A
- valve that opens to allow driving gas to exit the bellows housing (Inside of the bellows)
If youre EXHAUSTED you are inspiring a lot, therefore the exhaust valve works during inspiration
S8
20
Q
Factors that affect ventilation
A
- Compliance
- Leak
S9
21
Q
Compliance affects ventilation. What are the 2 types of compliances?
A
- system compliance: bent tube
- patient compliance: asthma, COPD, trendelburg, obese
S9
22
Q
- Where can a leak occur?
- How does a leak affect delivered tidal volume?
A
- around the tracheal tube or supraglottic device
- Leaks will cause a decrease tidal volume that can’t be compensated by the ventilator
S9
23
Q
Components of bellow ventilator
Components of bellow ventilators
A
- Driving gas supply and FGF [double circuit]
- Either O2, air, or mix
- Controls
- Alarms
- Pressure-limiting mechanism
- Bellows assembly: accordion-like device
- Housing
Housing has Driving gas, Bellows have FGF, CAP
S10-11
24
Q
Components of bellow ventilator
Some ventilators can switch between driving gases, when would they do this?
A
during a loss of pressure
S10
25
# Components of bellow ventilator
* Driving gas supply is equal to?
* Total Oxygen Used by anesthesia machine
* Driving gas is equal to minute ventilation
* Total Oxygen Used by anesthesia machine = Flow control [1-2L/min] + Vm 4-5L/min [breath the pt gets from the bellow] + driving gas 4-5L/min [gas in housing]
| S10
26
# Components of bellow ventilator
What do controls do in bellow ventilators?
* regulate flow, volume, timing and pressure
| S10
27
# Components of bellow ventilator
What does the driving gas do to the bellows?
* The driving gas is the gas *external* to the bellows that cause them to collapse.
| S10 Andy?
28
# Components of bellow ventilator
* What kind of alarm does the bellow ventilator have?
* What are the two standard alarms on the ventilator?
* Alarms: high, medium, and low priorities
* **Must have: low and high pressure alarms**
| S10
29
# Components of bellow ventilator
What is the most common cause of low-pressure ventilator alarms?
* Disconnection of a circuit
| S10 Lecture
30
# Components of bellow ventilator
What are examples of high-pressure ventilator alarms?
* Kinking of the ETT
* Occlusion of mask
| S10 lecture
31
# Components of bellow ventilator
* What is the pressure limiting mechanism ?
* What is a good set point/number ?
* limits inspiratory pressure
* 10 cmH2O above peak pressure with desired Vt
| S11
32
# Components of bellow ventilator
What is the housing of the below anesthesia ventilator made of?
What does it allow for?
How do you determine how much Vt is given?
* Clear plastic cylinder
* Allows movement of bellows to be observed
* Has scale on side for rough estimation of tidal volume
| S11
33
What are the 2 types of ventilators?
1. Bellow Ventilators
2. Piston Ventilators
| S12/14
34
Bellows are pneumatically driven, how do they work?
* Driving gas squeezes gas out of bellows into lungs
| S12
35
How/whendo the bellows refill?
* Fill on exhalation
* Exhalation and FGF in circuit refills bellows
| S12
36
What are the two kinds of bellow arragement?
Which one is safer?
* Ascending Bellows (standing): **safer**
* Descending Bellows (hanging)
| S12
37
What is the ascending bellows doing on inspiration and expiration?
* ascends on expiration
* descends on inspiration
| S12
38
What is the descending bellows doing on inspiration and expiration?
* descends on expiration
* rises on inspiration
| S12
39
Why are ascending bellows considered safer?
* If there is a disconnection in the circuit, the bellows will **fail to rise on exhalation**, which will trigger the CRNA to know something is wrong.
* For descending bellows, they will **continue to descend even if there is a disconnection d/t gravity.**
| S12
40
What are problems that can be encountered bellows?
* improper bellows seating
* hole in bellows
* scavenging system closed
| S13
41
What is the result of improper bellow seating?
inadequate ventilation
| S13
42
What is the result of having a hole in the bellows?
* alverolar hyperinflation/barotrauma
* if driving gas is O2, pts FiO2↑
* if driving gas is air, pts FiO2 ↓
| S13
## Footnote
1. As bellow collapses the gas goes into the housing instead of pt.
2. Can also cause barotrauma d/t driving gas pressure pushing in (gas in the housing leaks into the bellow)
43
what is the problem with scavenging sytem being closed?
waste gases vented to room/atmosphere
| S13
44
Components of piston ventilators
* mechanically driven motor
* like plunger of syringe
* no driving gas [single circuit]
* uses dramatically less gas [O2, air]
* doesnt alter Vt based on compliance
| S14
45
List the qualities of the piston ventilator
* Doesnt alter Vt based on compliance
* accurate tidal volumes
* very small piston chamber
* hidden on machine.. no visual ventilation
* very quite
4 V qualities: Vt, Very small/quiet, visual ventilation is hidden
| S14
46
What are probems encountered with the Piston ventilator?
* refills even with disconnection
* like descending bellows
* entrain room air during leaks
* it dilutes oxygen/volatiles
| S15
47
What is the most commonly used mode of ventilation?
* Volume control
| S16
48
What is volume control mode of ventilation?
What are the set parameters in volume control?
* Preset tidal volume is delivered (fixed parameter)
* The machine will give a set tidal volume regardless of the patient's condition
* Set parameters: Vt, RR, I:E ratio
| S16
49
Volume control mode can cause excessive ____ pressure.
* inspiratory
| S16
50
In volume control mode, what happens if pt initiates additional breaths?
* additional breaths at machine preset Vt
| S16
## Footnote
VT: 500 and RR 10. If pt initiates an extra breath (RR now 11) the extra breath will get Vt of 500.
51
What conditions would a volume control mode not be beneficial for the patient?
* Conditions with decreased compliance and FRC
* Obese/Pregnant patients
* Trendelenburg/Lithotomy procedures
* Patients with lung pathology
* Patients that need to be weaned from the vent
| S16- Andy
52
How much tidal volume should be delivered to a patient on a ventilator?
* 4-6 mL/kg
| S16- Andy
53
Describe pressure control ventilation.
What are the set parameters in pressure control?
* Preset pressure is quickly achieved during inspiration. [fixed parameter]
* Set: PIP, RR, and I:E Ratio
| S17
54
What happens to tidal volume in pressure control ventilation.
* Tidal volume changes with resistance and compliance
| S17
55
What will insufflation of the abdomen do to inspiratory pressure?
* Increase inspiratory pressure, which will cause a low tidal volume.
| S17-Andy?
56
What is the good thing about pressure control ventilation?
* This vent setting protects lungs from barotrauma of excess pressure
| S17-Andy?
57
What is the bad thing about pressure control ventilation?
* can cause atelectasis and hypoventilation
* *The pressure delivered in this mode might not develop enough tidal volume for the patient.*
| S17
58
What are ways to deliver more tidal volume in pressure control ventilation mode to patients with low lung compliance?
* Increase PIP
* Use Inverse I:E ratio, longer inspiration than expiratory time. The body will have time to adapt to increased pressure.
| S17- Andy
59
Describe Volume Guarantee Pressure-Control.
* Maintains tidal Volume by adjusting PIP over several breaths.
* Prevent sudden Tidal Volume changes d/t compliance
* Lost insufflation
| S18
60
What is Assist Control Ventilation?
* Predetermined negative pressure will trigger breath
* Breath is at preset tidal volume
| S19
61
What is Intermittent Mandatory Ventilation (IMV)?
* Mandatory ventilator breath is set
* Additional native breaths at variable tidal volume
* Allows breath stacking
| S19
62
What is SIMV?
* Synchronizes ventilatory-driven breaths with spontaneous breaths
* Provides backup to weaning ventilator
* **Best for weaning**
| S20
63
What is Pressure Support?
* PIP and inspiratory time set
* Vt equates to the native effort
* Need apnea alarm
| S20
64
Why cant standard ventilators be used in MRI?
* Standard machines have variable amounts of ferromagnetic substances
| S21
65
What are solutions for using a ventilator during an MRI?
* MRI compatible machines
* Anesthesia machine kept outside in hallway
* Machine bolted to wall
* Aluminum tanks or pipeline gas supply
**MAMA** what are the solutions for vents for MRI
| S21
66
General Hazards: What can cause ventilation failure?
* Fluid in electronic circuitry (excessive humidity)
* Leaking bellows housing
* Extremely high FGF
* Disconnection from power supply
FLED
| S22
67
General Hazards: How can there be a loss of breathing system gas?
* **Failure to occlude spill valve**
* **Leak in the system**
* Pipeline failure (lecture)
* Empty cylinder (lecture)
| S22
## Footnote
Need to do daily anesthesia machine check
68
General Hazards: What can cause incorrect ventilator settings?
* Incorrect settings!!! (easy to turn knobs)
- Inadvertent bumping
- Not adjusted for new case (preset at 700 & 10)
- Not adjusted for position/pressure changes
- Ventilator turned off for xrays (cholangiogram)
| S23
69
Advantages of a ventilator
* Allows anesthesia provider to devote energy to other tasks (free hands)
* Decreases fatigue
* Produces more regular rate, rhythm, and Vt
| S24
70
Disadvantages of a ventilator
* Loss of “feel” (reservoir bag)
* Components are hard to clean or fix
* Lack user-friendliness
* Older versions may not have all the desired modes
* Noisy or too quiet
* Expensive if it requires high-flow driving gases
Lost CLONE
| S25
71
What is the trace gas concentration?
* Concentration of a gas far below that needed for anesthesia or detected by smell
| S27
72
Trace concentration units
* PPM (parts per million)
| S27
73
100% of gas is how many PPM?
1,000,000, PPM
| S27
74
1% of gas is how many PPM?
10,000 ppm
| S27
75
Higher levels of trace gas concentration are seen where?
* Pediatric anesthesia
* Dental surgery
* Poorly vented PACU's
| S27
76
* What is the maximum TWA concentration (ppm) for anesthetic agents:
* halogenated agent alone
* nitrous oxide
* What is the maximum TWA concentration (ppm) for combo of halogenated + nitrous oxide: :
* Halogenated agent:
* Nitrous oxide?
* Dental facilities (nitrous oxide alone)
⭐️
| S28
## Footnote
kane said we need to know this slide!!!
77
What are the 6 common causes of OR waste gas contamination?
* Poorly fitting masks
* Use of uncuffed ETT
* Failure to turn off vaporizer
* Flushing circuit into room
* Filling vaporizers...spills
* Scavenging system leaks
PUFFFS
| S29
78
For years what did old studies conclude about trace gas exposure/vapor leaks?
* Spontaneous abortions
* Spontaneous abortion in spouses
* Infertility
* Birth defects
* Impaired performance
* Cancer/mortality
* Liver disease
* Cardiac disease
Cancer Spontaneously Injected Liver/Cardiac Into Births
| S30
## Footnote
These negative side effects of gas exposure has been mitigated with the scavenger system
79
Scavenging system function.
* Removes the collection of gases from equipment used to administer anesthesia or exhaled by the patient.
* Removal of these gases outside the work environment
* Have active and passive systems
| S31
80
Describe the passive scavenging system:
* Location:
* Passage of airflow
* Where is volume exhausted?
* Where is the disposal tubing?
* Attached to room ventilation
* Air flows through room after being filtered and adjusted for humidity and temperature
* Entire volume is exhausted to the atmosphere.
* Disposal tubing from the anesthesia machine is attached to the exhaust grill and removed with room air.
* very economic; uncommon
| S32
81
Describe the active scavenging system:
* Location:
* What must it be able to provide?
* What should be close to the anesthesia machine?
* Attached to central vacuum system
* Must be able to provide high volume (30L/min)
* Need plenty of suction outlets and close to anesthesia machine
| S33
82
How do we prevent excessive trace gas in the procedural room?
* 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 (passive system) as possible
| S34
83
What are causes of a hypoxic inspired gas mixture?
* Incorrect gas in the pipeline
* Incorrectly installed outlets
* Oxygen tubing or hoses attached to 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
| S36
84
How does Hypoventilation occur on the ventilator?
* Insufficient gas
-switch from pipeline to cylinder
-replace cylinder
* Obstruction
* Leaks
* Main machine power off
* Breathing system leaks (disconnections)
-absorbent, connectors, gas sampling
BLO MI if I hypoventilate
| S37
85
What are possible reasons why we would have blocked inspiratory/expiratory paths?
* Mask wrapping
* Absorbent wrapping
| S38
86
How can the ventilator cause hypercapnia?
* Hypoventilation
* Excessive dead space
* Absorbent failure (increased baseline on etCO2)
* Defect coaxial system
**Head** causes hypercapnia
| S39
87
How does an anesthetic agent overdose occur with the anesthesia machine?
* Vaporizer accidentally on
* Overfilled vaporizer
* Incorrect agent in vaporizer
* Interlock system failure
* Tipped vaporizer
Vent Overdoses If It Tips
| S40
88
What are ways to prevent inadvertent exposure to volatiles?
* Change breathing system hoses and bag
* Change fresh gas supply hose
* Change absorbent
* Use very high oxygen flows to flush the machine
* Remove vaporizers
* Use an auxillary flowmeter for supplemental oxygen
| S41
