1
Q
What are we manipulating w/ pre-oxygenation?
A
Functional Residual Capacity (FRC)
- Expiratory Reserve Volume (ERV) + Residual Volume (RV)
- Increasing this allows more time for intubation
2
Q
What are the differences between an ICU vent and an Anesthesia vent
A
Anesthesia
- Bellows or piston driven
- Semi-closed circuit
- Exhaled gases to scavenger
- Need reservoir for exhaled gases
- Flowmeters plus vaporizers
ICU
- Usually piston
- Open circuit
- Exhaled gases to atmosphere
- No reservoir for exhaled gases
- Oxygen blenders
3
Q
What are 3 Advantages of the Ventilator
A
- Provider free for other tasks
- Decrease fatigue
- Produce more regular rate, rhythm, and TV (creates more hemodynamic stability)
4
Q
Disadvantages of the Ventilator
A
- Loss of feel (#1 reason)
- Cannot physically push the breath into the patient and therefore cannot feel the compliance - Older versions have less features
- Components are hard to clean and fix
- Not user friendly
- May be too noisy or too quiet
- May require high driving gas flows which is $$$
5
Q
What is Barotrauma
A
Injury resulting from high airway pressure
6
Q
What is Compliance
A
Ratio of a change in volume to a change in pressure
- Expressed in ml/ cmH2O
- Lungs, chest wall, breathing tubes, and reservoir bags have compliance
7
Q
What is Continuous Positive Airway Pressure (CPAP)
A
Airway pressure maintained above ambient during spontaneous respiration
8
Q
Label the contents of one breath cycle
A
- Expiratory Flow Time: time from beginning to end of expiration
- Expiratory Pause Time: time from end of expiration until inspiration begins
- Expiratory Phase Time: add the two time above
- Inspirations Flow Time: time from beginning to end of inspiration
- Inspiration Pause Time: time during which lungs are held inflated at a fixed volume/ pressure (zero flow)
- Also called inspiration hold, inspiratory plateau
- Inspiratory Phase Time: add the two times above
9
Q
What is I:E ratio
And what patients would you use it for?
A
Ratio of inspiratory phase time to Expiratory phase time
- Typically exp. phase longer but if done in reverse then it is called
- Inverse ratio ventilation
- Normal = 1:2 — 1 sec to inspire, 2 sec to expire
- Reverse = 2:1
Patient’s with disease states: emphysema, asthma, COPD
10
Q
What is minute volume?
A
Sum of all tidal volumes in one minute
11
Q
What is Peek Pressure?
A
Maximum pressure during inspiratory phase time
12
Q
What does PEEP stand for and what is it?
A
Positive End Expiratory Pressure (PEEP)
- Airway pressure above ambient at end of Expiratory phase in controlled ventilation
- APL valve in spontaneous breathing patients
- Patients under anesthesia can’t sigh or produce surfactant
13
Q
What is Resistance?
A
Driving pressure to change in flow rate
- cmH2O/L/sec
14
Q
What is a Sigh?
A
Deliberate increase in TV for 1+ breaths
- Patients who are spontaneously breathing do this as a form of PEEP
- Patients on the ventilator can’t do this
If a patient is desating d/t no ventilation give a sigh to re-expand alveoli
15
Q
What is Work of Breathing?
What are 3 signs ?
A
Energy expended by patient/ventilator to move gases in and out of lungs
- Joules/L
- WOB = grunting, accessory muscle use, retractions, belly breathing, nasal flaring, increased respiratory rate
16
Q
What are 3 factors that affect Tidal Volumes?
A
- Fresh Gas Flow
- in older machines: increased flow - increased RR - increased I:E = increased TV
- New machines divert extra FGF during inspiration - Compliance
- decrease compliance = decrease TV
- Stiff chest harder to get Vol. in
- New machines compensate for compliance in the machine checkout procedure but changes in circuit configuration (i.e. adding length) will result in inaccuracy of compensation - Leak
- ETT/LMA leak can not be compensated for by ventilator
17
Q
Optimal vent setting provide what?
List 5
A
- Distending pressures
- Alveolar recruitment
- V/Q matching
- Homogeneity
- Prevention of Ventilator Induced Lung Injury (VILI)
- Research says w/ better hemodynamics there is decreased mortality & MODs
18
Q
What are the 4 main components of a Bellows Ventilator?
A
- Driving Gas Supply
- Pneumatically powered but electronically controlled
- Needs driving gas, air or O2 ($), do not use during power failure d/t cylinder use being short lived
- Controls
- Regulates flow, Volume, Timing, & Pressure
- Alarms
- REGULATION: must have both high and low pressure alarm
- Pressure limiting mechanism
- REGULATION: adjustable mechanism to limit inspiratory pressure
- potential for operator error
- Prevents barotrauma
- Set inspiratory pressure 10 cmH2O above peek pressure with desired TV
- REGULATION: adjustable mechanism to limit inspiratory pressure
19
Q
Why would the alarm for high Peek Inspiratory Pressure be going off?
A
- Decrease compliance in the chest (Broncospasm)
- Surgeons open retractors more & add more padding in the chest cavity
- Could be someone leaning on the patient
- Adding air into the belly (laproscopic cholecystectomy)
- Coming off paralytic or anesthesia is light
- Breath stacking
20
Q
What are the 3 safety valves in the Bellows assembly and what do they do?
A
- Exhaust Valve
- opens to allow gases from the housing chamber into the environment on beginning of exhalation (does not contain volatile) - Spill Valve
- allows excess FGF inside Bellow (accordion) to be sent to scavenging system during end of exhalation (contains volatile)
- this prevents extra pressure/ volatile to go to the patient - Safety Relief Valve
- expels excess gas from housing if driving pressure too high, will see in Mid-inspiration
21
Q
How are Piston Driven Ventilators different that Bellows?
A
- Electronically driven
- Reservoir bag not isolated on exhalation but is on inhalation
- Reservoir bag used to modulate pressures in the system = prevent negative inspiratory pressure (safety feature)
- Inspiration pushes gases into breathing system and excess into reservoir bag
22
Q
What are 2 Advantages of the Piston Ventilator?
A
- Decrease cost due to no driving gas
2. More accurate TV at constant velocity
23
Q
What is the main disadvantage of the Piston Ventilator?
A
Air entrainment from disconnect may not generate alarm
- The disconnect could come from either the circuit at the point of the CO2 line or a flutter valve stuck open
- If this occurs we worry about awareness d/t dilution
24
Q
What are some considerations when taking a patient to MRI and they are on a ventilator?
A
- MRI compatible machine - Cannot use a standard machine b/c of ferromagnetic substances
- If you have to use an anesthesia machine have to keep it in the hallway — have to have extension tubing
- Use pipeline supply - cannot take cylinders in or have to have nonferrous cylinders
25
What are 4 main things that can go wrong with ventilators?
1. Ventilation Failure
- no power supply, too high FGF, fluid in electronic circuitry, leaking bellows, left on for periods long than 24 hrs
2. Loss of Breathing System Gas
- Failure to occlude spill valve (bellows) (all flow sent to scavenger(?), system leak (less apparent in descending bellows, that’s why they are obsolete)
3. Incorrect Settings
- not adjusted for new case, not adjusted for new position/pressure changes, vent turned off for x-ray
4. Pressure Problems
- O2 flush on inspiration w/ APL valve closed (use) = Barotrauma (high pressure O2 flush = 35 - 75 L/min)
- Insufficient Expiratory time = auto Peep - breath stacking, barotrauma
26
What are the most common Vent Modes?
| 7
1. Volume Control
2. Pressure Control
3. Assist Control
4. Spontaneous Intermittent Mandatory Ventilation (SIMV)
5. Pressure Support Ventilation (PSV)
6. Constant Positive Airway Pressure (CPAP) & Bi-level Positive Airway Pressure (BiPAP)
7. Airway Pressure Release Ventilation (APRV)
27
What 2 Factors do ventilator settings depend on ?
1. Compliance: ability to stretch/expand the chest
2. Gas exchange: oxygen delivery at alveoli
- Can assess these via blood gases
28
If your patient’s blood gas read:
- pH 7.4, PCO2 45, PaO2 50
What would you change on your vent setting?
Mode, Vt, Peep, RR, FiO2, I:E
Add Peep
| - If you just increase FiO2 & they have collapsed alveoli you are not going to get the full benefit of O2
29
How do you calculate a normal PaO2?
Take the FiO2 x 5 and it gives you what the PaO2 should be according to the FiO2 setting
- Normal PaO2 = 80 - 100
- this is a range where all systems work the best
30
What 2 ventilator settings would you use if your patient was not spontaneously breathing?
Positive Pressure Ventilation:
1. Volume Control
2. Pressure Control
31
Volume Control Ventilation
- Preset tidal volume on a timer
- Pushes vol. into patient no matter what
- Vt does not depend on patient effort, resistance, or compliance changes
- Volume does not change — Pressure varies
- Good for paralyzed patients
- Inspiratory phase can be limited if excessive airway pressures are reached
- Inspiratory flow too high = High PIP (Peek Inspiratory Pressure)
- giving them a breath too quick
- Change in compliance = change in PIP
32
Consideration for exhalation on Volume Control Ventilation
- Exhalation is passive
- requires appropriate time (I:E= 1:2 or 1:3)
- Dependent on patient’s resistance & elastance (pressure required to inflate lungs) or compliance
- Pts w/ an increase need longer time to exhale
- At the end of expiration airway pressure returns to atmospheric pressure or to what PEEP is set at
- If not allowed enough time to exhale = high intrathoracic pressure
= decreased venous return & cardiac output
= increased risk of barotrauma
= displacement of the diaphragm & inspiratory muscles from their optimal functional position
33
Pressure Control Ventilation
- Vent will deliver the breath at a preset pressure in a given time
- Delivers breath no matter the patient’s effort
- Pressure is set - Volume varies
Good for:
- Lung injury
- Single lung ventilation
- SUPRAGLOTTIC AIRWAYS (if you give a set vol. the extra could go into belly = aspiration)
- good to have a set pressure for LMAs (20 cmH2O)
- Partial airway obstructions
- b/c the decelerating flow patterns provide the best delivery of gas to the alveoli
34
Which vent mode in the sedated patient is better for alveolar recruitment?
Pressure control
- it is a more consistent & uniform way to give breaths
- maximizes oxygenation for the patient
- homogeneity (all the same)
35
Which vent mode is preferred if you have to have a set MV (minute ventilation)?
Volume control
- Minute ventilation = RR x Vt
- normal is 4-6 L/min
- RR and Vt are present in VC vs. PCV when Vt fluctuates
36
In a spontaneously breathing patient what ventilator modes are used?
And which ones are for Sedated & Non-sedated pts.
Negative Pressure Ventilation:
Sedated patients:
1. Intermittent mandatory ventilation (IMV)
2. Assist Control (AC)
3. Synchronized intermittent mandatory ventilation (SIMV)
4. Pressure support ventilation (PSV)
5. Airway pressure release ventilation (APRV)
Non-sedated patients:
1. CPAP
2. BiPAP
3. APRV
37
Benefits of using synchronized breathing ventilator modes:
1. restoring gas exchange
2. Unloads the WOB/ resp muscle use
3. Relieving dyspnea - assist the patient if they are weak but still allow them to use their diaphragm
In the critically ill patient’s:
1. Reduces sedation and paralysis
2. Minimize cardiovascular side effects of mechanical vent.
3. Decreases disuse diaphragm atrophy
4. Improves V/Q mismatch (uniform O2 delivery
38
Synchronized Intermittent Mandatory Ventilation (SIMV)
- The vent is synched with the patients own breathing
- It detects patient driven inspiration to deliver:
- Vt or pressure
- Rate
- minimum mandatory ventilation rate
- Does not require I:E ratio
- Good for facilitating emergence from anesthesia
- allows for titration of medication so we don’t snow them
- If settings too high = can knock out the patients spontaneous drive to breathe
39
Assist Control
- Vent delivers a preset Vt whether the patient initiates it or not
- VC/PCV on steroids - accentuates every breath
- Ideal for muscle recovery b/c the vent does most of the work
- Good for: (ICU pts)
- Post resuscitation
- Acute resp distress syndrome (ARDS)
- Bad for: (OR, especially on emergence)
- Anxious patients who frequently trigger the vent = hyperventilation
- Needs adequate time for exhalation or it increases the risk of barotrauma or pos. Drive ETCO2 down and disrupt pH
40
Pressure Support Ventilation
- Provides positive pressure to patient initiated breath
- No set R
- Vt determined by:
- PS level
- lung characteristics
- Patient effort
- No effort = no breath
Bad for:
- Hyperventilating patient = breath stacking
Good for:
- reducing the WOB, increasing FRC, oxygenating obese pts, supraglottic airways, weaning, vent harmony
41
Airway Pressure Release Ventilation (APRV)
- Rarely used
- Inverse ratio of inhalation pressure
- Typically 10:1 (5 sec : 0.5 sec)
- Used mainly as a rescue therapy for ARDS
- Extra time to inhale
- Has to be carefully monitored so you don’t have breath stacking
42
Benefits of PEEP/CPAP/BiPAP (4)
1. More uniform distribution of Vt
2. Increased FRC
3. Better arterial oxygenation
4. Redistribution lung water
5. Reduced V/Q mismatch
43
What are 5 protective lung strategies
1. Low Vt = 6- 8 mL/kg PBW)
2. Maintaining Pplat less than 30 cmH20 (if pleural pressure is normal)
3. Use PEEP & recruitment maneuvers (sigh)
4. Reduce FiO2
5. Permissive hypercapnia (controlled increase in PCO2, reduces inflammation, & relaxing smooth muscles)
44
5 Reasons why you might be getting a Vent alarm
| DOPES
```
D = Dislodgment
O = Obstruction of ETT - mucus plug, bitting, kink
P = Pneumothorax
E = Equipment malfunction
S = Stacked Breaths or dis-synchrony
```
45
Low Peak Pressure Alarm
Think Leak
- Problem = can’t generate pressure needed to oxygenate patient
- Common issue = ETT too high or dislodged, cuff leak, chest tube leak
- Least likely issue = bronchopulmonary fistula
46
High Pressure & normal Plateau Alarm
Think Resistance
Problem = smaller diameter for air flow
Common issues =
- Bronchospasm
- Mucus plug
- Aspiration
- Hemoptysis (blood in airway)
- Water condensation
- Kink
47
High Peak Pressure & High Plateau Alarm
Think Compliance
Problem = lungs resisting ventilation
Common issues =
- Worsening pneumonia
- Pulmonary edema
- Auto PEEP
- Right Mainstem intubation
- Tension Pneumothorax
Least likely issue =
- Diaphragm injury
- Compartment syndrome
- Circumferential burn (constriction)
48
Hypoxia with normal curve
Think Shunt
Problem = increase dead space ventilation or poor perfusion
Common issues =
- Pulmonary embolism
- Hypovolemia
- Shock
- AV fistula
Least likely issues =
- Intracardiac shunt (PFO)
49
What is the first thing you should do if you have High Airway Pressure?
Disconnect from the circuit & manual vent while you locate the problem
- if you leave patient connected to high pressures it will cause barotrauma
Intro To Anesthesia
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Decks in class (5)
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