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Clinical Pract Review - Basics of Mech Ventilation
Terms in this set (42)
What was the first lung that created negative pressure in children?
The iron lung in Boston's children hospital (1928)
What is the goal of mechanical ventilation?
To achieve maximum oxygenation with the least trauma; ↓ PaCO₂ & ↑ PaO₂
Bellows use ______ for the drive gas to compress the bellows
Piston driven ventilators use a ______ to compress the bellows
Pipeline pressure has no effect on the following type of ventilation:
What is the most common ventilator mode?
What is volume control ventilation?
fixed volume at constant flow & variable pressure
How is PIP kept low with volume control ventilation?
low inspiratory flows
What can result from too low inspiratory flow with volume control ventilation?
What can result from too high inspiratory flow with VCV?
TV reached before end of inspiratory time = inspiratory pause
How can risk of lung injury be decreased with VCV?
by ↓ set pressure limit
The following reflects compliance in VCV?
Plateau pressure-resting pressure during inspiratory pause
What are the advantages of VCV? (2)
Maintains constant TV, precise control of PaCO₂
What are the disadvantages of VCV (2)
Potential for ↑ airway pressure & acute lung injury; inability to compensate for leaks
What are initial settings for VCV? (RR, TV, limits, PEEP, I:E ratio)
RR: 6-12 bpm
Pressure limit: 30-35 cm H₂O
PEEP: 0 cm H₂O
I:E: 1:2 for 10 bpm
What is pressure controlled ventilation?
fixed pressure at variable volume
How can atelectasis and barotrauma be avoided with PCV?
adjust target pressure for reasonable TV
What does a square waveform imply with pressure control mode?
constant airway pressure & will limit the pressure
Up to how much volume can be delivered with PCV?
When is pressure control mode of ventilation most useful? (9)
Unsealable airways (kids, bronchopleural fistulas)
Increased insp flow demands
Poor oxygentation (ARDS/ALI)
Increased peak airway pressures
What are the advantages of pressure control ventilation? (5)
1. Variable DECELERATING flow pattern for improved gas exchange
2. Reduces peak pressure and risk of BAROTRAUMA
3. Insp flow and time are independent of each other
4. More EVEN distribution of air regardless of compliance
5. Compensates for LEAKS
What are the disadvantages of pressure control ventilation? (4)
1. Requires closer monitoring
2. Doesn't guarantee MV or TV
3. Increased risk of AutoPEEP (pressure builds up in alveoli-stacking breaths)
4. Hypoventilation secondary to changes in lung compliance and resistance
How should the peak pressures be calculated with pressure controlled ventilation?
difference between the end-expiratory plateau pressure & set PEEP (should be < 20cm H₂O)
What should the PEEP be set at with pressure controlled ventilation? (health & with airway ds)
healthy: 0-5cm H₂O
airway ds: 7-12cm H₂O
What is SIMV?
Synchronized Intermittent Mandatory Ventilation (SIMV)
1. Assisted but not controlled RR
2. Allows pt to breath spontaneously but doesn't assist
3. Allows for assisted breaths if pt initiates along w/ set rate
What ventilator mode allows for assisted breaths of patient initiates their own breath?
What ventilator mode prevents bucking and breath stacking and is used in emergence?
What settings should be set with SIMV other than RR & TV?
sensitivity & trigger
What ventilator mode helps augement inflation volumes of spontaneous breaths?
Pressure support ventilation
What is the preferred with use of a supraglottic device?
Pressure support ventilation
What could cause inappropriate triggering with pressure support ventilation? (3)
leaks, patient movement, cardiac contractions
What ventilator mode is useful for increasing FRC; recruiting collapsed alveoli and improve V/Q matching?
What is PEEP?
Positive End Expiratory Pressure;
Pressure is applied at end of expiration to maintain alveolar recruitment
What are the disadvantages of PEEP? (4)
1. Increases intrathoracic pressure
2. Long-term may lead to ARDS
3. Pneumothrorax, pulmonary edema
4. ↓BP, ↓Venous return & CO
What ventilator mode helps in left side heart failure?
What is CPAP?
Constant PEEP, spontaneous breathing
What is I:E ratio?
Ratio of the inspired phase time to expiratory phase time. I:E of 1:2 means inspiratory time is 1/3 of ventilatory cycle
What mode of ventilation is more desirable in kids <10kg and why?
PCV: limits peak pressures, improves lung distribution, rapid improvement in lung compliance & oxygenation may be seen
What may lead to hypoventilation with mechanical ventilation? (6)
1. ventilator failure
2. breathing system gas loss
3. incorrect settings (defaults, previous pt settings)
4. ventilator turned OFF
5. flow obstruction
6. PEEP (may ↓ TV)
What are the hazards of mechanical ventilation? (8)
4. excessive airway pressure
5. negative pressure during expiration (hanging bellows)
6. alarm failure
7. electromagnetic interference
8. loss of electrical power
What can holes in bellows, ↑ inspired O₂, and ↓ anesthetic gas lead to?
What can lead to negative pressure during expiration?
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