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MV - Quiz #5

Mechanical Ventilation Lecture #4

What is the drive mechanism of a ventilator? System used by vent to convert power to work (output control), transmits or converts input power to useful ventilatory work; provides mechanical force needs to generate flow and deliver VT
What are the different types of drive mechanisms? Piston, Reducing Valve, Bellows, Microprocessor-controlled pneumatics, power mechanisms
What are the different types of power mechanisms? Pneumatic, electric, combined
What is the pneumatic power mechanism? Uses pressure gas as a power source, requires 50 psi connection
What is the electric power mechanism? Uses electricity as power source, always plug vent into RED outlet
What is a combined power mechanism? Uses both gas and electricity as power source, needs 50 psi and outlet to work
What is the ventilator control circuit? System that governs ventilator drive mechanism; generates waveform (inspiratory flow pattern)
What is an open loop control circuit? RCP selects desired output (volume or pressure desired); machine then achieves that output without further input from vent or RCP
What is a closed loop control circuit? RCP selects desired output...input is then adjusted to match output; vent measures a specific parameter (flow, pressure, or volume) continuously
What is a mechanical control circuit? Uses levers, pulleys, and cams to control ventilator output
What is a pneumatic control circuit? Valves, nozzles, ejectors, and diaphragms to control pressure output
What is an electric control circuit? Simple switches control VT delivery
What is a fluidic control circuit? Gas flow and pressure controlled without moving parts; uses flow splitters to direct flow of gas
What is an electronic control circuit? Most modern vents - uses resistors, diodes, transistors, and microprocessors to control output; gives greatest flexibility for RCP control
What are the limiting parameters of a ventilator? Alarms and safety measures, parameters that do not cycle from inspiratory to expiratory phase, will limit inspiration if preset value is reached, can be pressure, volume, or flow limited
What are the basic vent settings? RR, mode, VT, FiO2, Peak flow, Sensitivity
What is the RR on the ventilator? Number of time the machine will deliver a breath to the patient (AKA frequency)
What is the mode on the ventilator? Determines how the breath is delivered and how much support the patient will receive from the vent and how much the patient can do on their own
What is the tidal volume setting on the ventilator? Volume of breath delivered, how big of a breath they're getting in VCV; In PCV = achieved VT (varies)
What is the FiO2 setting on the ventilator? Amount of O2 delivered with each breath
What is the peak flow (PF, flow, flow max) setting on the ventilator? Speed of the delivered gas on inspiration, how fast the air is being pushed in, controls I:E ratio, measured in LPM
How does an increased peak flow effect I:E ratio? Decreased I time, Increased E time
How does a decreased peak flow effect I:E ratio? Increased I time, Decreased E time
What does a longer E time prevent? Air trapping (auto-peeping)
What is the sensitivity setting on the ventilator? Amount of negative pressure that must be generated to begin inspiration, determines how easy or difficult it is for patient to initiate inspiration ; only for when patient initiates the breath in between machine breaths (or all breaths on CPAP)
What does the P on a vent represent? Pressure
What does an I on the vent represent? Inspiration
What does an E on the vent represent? Expiration
What does a V on the vent represent? Volume
What does a V with a little dot above it on the vent represent? Flow or minute
What does an F on the vent represent? Frequency
What does a T on the vent represent? Tidal or time
What are the 4 phases the vent must perform to provide a complete breath? Inspiratory phase, inspiratory-expiratory changeover, expiratory phase, expiratory-inspiratory changeover
What is the inspiratory phase? Drive mechanism creates positive pressure gradient (aka trigger - time, pressure, or flow)
What is the inspiratory-expiratory phase? How vent ends inspiratory phase just before expiratory phase (aka limit or cycle); ended by: volume, time, pressure, flow, high pressure limit
What is the expiratory phase? Passive expiration, all expiration is passive on a ventilator (just like spontaneous breathing)
What is the expiratory-inspiratory phase? Completion of expiration until next inspiratory phase begins from initiation by patient or ventilator (depending on mode)
How is a breath triggered on the ventilator? Signal is sent to begin inspiration, either time, pressure, or flow triggered
What is time triggered? Inspiration initiated when a preset time interval has been reached, controlled by RR, ONLY machine breaths
What is pressure triggered? Inspiration initiated when ventilator sense patient's spontaneous inspiratory efforts; controlled by pressure sensitivity, ONLY patient breaths
What is normal sensitivity? -1 to -5 (-2 is ideal)
How does a higher sensitivity (-5) effect ventilation? Less sensitive the setting, harder to initiate a breath...more they have to pull back
How does a lower sensitivity (-1) effect ventilation? More sensitive the setting, easier to initiate breath...less they have to pull back
What should be done if the patient is having difficulty initiating a breath is pressure triggered mode? Decrease sensitivity #, making vent MORE sensitive
What is flow triggered ventilation? Low amounts of continuous air flows through circuit, as patient tries to initiate breath, amount of flow at patient wye changes, this triggers inspiration, controlled by flow (sensitivity) - more flow = easier to inspire, ONLY patient breaths
What are the 5 cycle types? Volume, time, pressure, flow, high pressure limit
What is cycling on the ventilator? Parameters on the vent that terminate inspiration, how the vent ends the breath
What is volume cycled ventilation? Inspiration ends when preset VT is reached, volume is constant, PIP is variable
What is the advantage of volume cycled ventilation? Guaranteed VT
What is the disadvantage of volume cycled ventilation? PIP may increase too high (causing barotrauma); important to monitor PIP
What is time cycled ventilation? Inspiration ends when preset inspiratory time has been met, volume is variable
What is the advantage of time cycled ventilation? Best method to control I:E ratio
What is the disadvantage of time cycled ventilation? VT dependent on lung cL, RAW (atelectasis), very important to monitor exhaled VT
What is pressure cycled ventilation? Inspiration ends when preset PIP is reached, volume is variable (directly with lung cL and indirectly with RAW) , flow and pressure are constant
What is the advantage of pressure cycled ventilation? PIP (and MAP) is controlled (reduces barotrauma; PIP < 50 cmH2O and MAP < 30 cmH2O are optimal
What is the disadvantage of pressure cycled ventilation? Decreased cL and increased RAW = lower VT (can build up CO2; atelectasis), need to monitor exhaled VT (most important to monitor!)
What is flow cycled ventilation? Inspiration ends when inspiratory flow stops (pressure is equal in and out), used during spontaneous breathing
What is the advantage of flow cycled ventilation? Decreased RAW due to less positive pressure being forced in
What is the disadvantage of flow cycled ventilation? Patient may not be able to regulate breathing well enough to normalize CO2
What is high pressure limit cycled ventilation? Safety measure (alarm setting), ends inspiration when high pressure limit value is reach, even if full VT is not delivered, used with volume ventilation to protect against barotrauma, proper settings are essential-do not raise HPL for convenience
What are the four inspiratory flow patterns? Square (constant), accelerating (ascending), decelerating (descending), sine (sinusoidal)
What does the inspiratory flow (peak flow) pattern tell us? Determines how the flow is distributed during inspiration
What is the square waveform? Peak flow delivered immediately at onset and maintained throughout inspiration, abruptly ends (cuts off) flow at start of expiration
What is the accelerating waveform? Peak flow ramps up slowly until peak flow is reached; abruptly ends (cuts off) flow at start of expiration
What is the decelerating waveform? Peak flow delivered immediately at onset, then slowly tapers down
What is the sine waveform? Flow starts slow, goes to peak flow, then slowly back down; most closely resembles spontaneous breathing
Created by: ashconrad417