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25 Cards in this Set
- Front
- Back
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What is PEEP?
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Positive End Expiratory Pressure
physiological = 3 to 5 cmH20 keeps alveoli inflated Expiration maneuver |
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What is auto-PEEP?
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intrinsic or inadvertent PEEP
result of too short E time air trapping --> increased PCO2 |
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Describe PIP
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Peak Inspiratory Pressure
Pressure required to force the gas through the resistance of the airways and the gas volume as it fills the alveoli |
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Describe Plateau Pressure
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Pressure measurement taken after a breath has been delivered to the pt and before expiration has begun
used to measure Cs of alveoli |
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What is elastance?
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The tendency of an object to return to its original state after being stretched-
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Define pulmonary compliance.
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change Volume / change Pressure
l/cmH2O how easily the lungs expand normal = 0.1 l/cmH2O c ETT = .04 - .05 l/cmH2O |
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How is pulmonary compliance measured?
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use Plateau Pressure
Cs = ExhVt/ (Pplateau - PEEP) |
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What is resistance?
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AKA: frictional forces
Raw = PTA/flow (sec) PTA = PIP- Pplateau normal = 0.6 - 2.4 cmH2O/l/sec |
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How can resistance be manipulated?
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changing length and diameter of tube
increase length = increased R increase diameter = decreased R changing flow rate increase flow = increased R |
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Normal values for resistance.
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non-intubated = 0.6 - 2.4 cmH2O/l/sec
intubated = 5-7 cmH2O/l/sec |
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Normal values for compliance
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non-intubated = 0.1 l/cmH2O
intubated = 0.035 - 0.5 l/cmH2O |
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What are time constants?
How are the calculated? |
The rate at which individual lung units fill or empty
Product of compliance and resistance C*R normal = 0.1 sec |
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How do compliance and resistance affect time constants?
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increased R, increased C = Long TC
decreased R, decreased C = Short TC |
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How many TC's represent 95% filling or emptying of the lung?
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3
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How are ventilators pneumatically powered?
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Depend entirely on a compressed gas source for power
50 PSI Like the Bird |
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How are ventilators electrically powered?
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Rely on electricity to function
On/Off switch controls I,E, flow and alarms |
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How do ventilators use combined power?
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Use both power sources
One or two gas sources (variable FiO2) Electric: internal functions Gas: provide energy to deliver breath |
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Describe the Internal Circuit, including both the single and double circuits
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Single: allows gas to go directly from power source to pt. Currently used.
Double: generates gas flow that compresses another mechanism |
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Pressure-controlled vs. Volume-controlled breaths
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Pressure-Controlled: volume and flow may vary depending on pt's lung characteristics
Volume-Controlled: pressure varies depending on lung characteristics |
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Define mandatory mechanical breaths
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Started, controlled and ended by ventilator.
Ventilator does ALL WOB |
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Define assisted mechanical breaths
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Started by pt. but controlled and limited by ventilator
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How is a breath triggered? With pressure and flow?
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Pt. triggering
vent can "sense" attempts to breath. Negative P or flow will trigger vent to begin inspiration |
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How is a breath "limited"? With what variables?
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Inspiration can be timed (ventilator triggered)
Can also control max. pressure, volume or flow. Doesn't end I just limits variables |
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What is the difference between Pressure-limiting and Pressure-cycling?
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Limiting: max P is set as a safety feature, will never exceed, but doesn't end I
Cycling: when max P is reached I ends |
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How does CPAP or PEEP improve oxygenation?
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CPAP: mode or ventilation, but pt is spontaneously breathing
PEEP: mehanically vented pt. both prevent early airway closure and increase FiO2 |
