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16 Cards in this Set
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Assignment 3 |
Egan page 1027 to 1033 Chapter 46 page 333 to 334 |
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Inspiratory time: expiratory time (I:E ratio) |
Low Compliance (change in volume over change in pressure is compliance) :Such as ARDS, the I:E ratio can be changed to improve distribution of ventilation and oxygenation :For ARDS you would push gas in slow to improve oxygenation, for COPD you would push gas in fast to improve oxygenation by increasing exhalation time and expiratory breaths :Example 1:2 or 1:1
Low elastance (obstructive patients have this) so they inflate nicely, but do not deflate cause of low elastance :air trapping, as seen in COPD, high flowrate with higher I:E ratio allows for the patient to empty their lung better (1:4 or 1:5)
Compliance = 1/elastance
HIgh elastic recoil means stiff lung and poor complinace (pulmonary fibrosis)
Poor elastance means high complinace (COPD) |
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Fraction of inspired oxygen |
The goal of oxygen therapy is provide the lowest possible fraction of inspired oxygen (FiO2) to meet metabolic needs :That is necessary to meet oxygenation goals should be used :The same is true for mechanical ventilation
Appropriate FiO2 will decrease the likelihood that adverse consequences such as: :Absorption atelectasis (too high FiO2, o2 washes out the nitrogren(the filler gas) which keeps the alveoli distended and results in collapsed atelectasis :Airway or parenchymal injury
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Modes of ventilation: the Basiccs (must know these) |
Assist control ventilation (volume Control) ACVC Assist control Ventilation (Pressure control) ACPC Pressure support ventilation PSV Intermittent mandatory ventilation volume control (synchronized) IMV Intermittent mandatory ventilation pressure control (synchronized) |
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Assist control ventilation |
A set tidal volume (if set to volume control) or a set pressure and time (if set to pressure control) is delivered at a minimum rate, (using this mode, a patient can trigger a breath as often as they want, when they do trigger a breath, they are assisting) Every breath is a ventilator breath, but the patient has the ability to trigger a breath. (the control part of this is, they will get a minimum set rate if they don't trigger the breaths)
Additional ventilator breaths are given if triggered by the patient
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Pressure support ventilation |
The patient controls the respiratory rate, Ti, inspiratory flow and Vt during inspiration. (all we set is the pressure)(this is spontaneous in pressure) PSV provides the patient support to overcome the increased work of breathing. (PSV is an inspiratory mode) :imposed by the disease process :Endotracheal tube :The ventilator circuitry |
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Intermittent mandatory ventilation |
Breaths are given at a set minimal rate: mandatory However if the patient chooses to breathe over the set rate, no additional ventilator breath is given :SIMV is that it allows patients to assume a portion of the ventilatory work :originally invented for ventilator weaning (with assist control, every breath is a ventilator breath even the ones initiated by the patients, but with this, not all breaths are ventilator breaths so spontaneous breaths interspersed with mandatory breaths) :Spontaneous breaths are always pressure supported (Rarely used if ever) |
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Intermittent mandatory ventilation |
SInce SIMV is usually associated with greater WOB than AC, it is not used as the initial ventilator mode Like AC, SIMV can deliver set tidal volumes (volume control) or a set pressure and time (pressure control) Decreased mean intrathoracic pressure generated by spontaneous efforts leads to increased venous return, which leads to increased cardiac output |
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Mode comparisons in book |
Assist control AC: advantages is it reduced work of breathing compared to spontaeous breathing
AC Volume ventiation: advantages is it guarantees delivery of set tidal volume
AC Pressure control ventilation: Advantages is it allows limitation of peak inspiratory pressure and oxygenaton (PCV)
Pressure support ventilation: advantages is patient comfort and improved patient ventilator interaction
synchronized intermittent mandatory ventilation (SIMV) advantage is less interference with normal cardiovascular function (two types of breath are spontaneous breaths and ventilator breaths |
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Disadvantages of each mode |
ACV: potential hemodynamic effects, may lead to hyperventilation AC Volume ventilation: may lead to excessive inspiratory pressure AC Pressure control ventilation: hyper or hypoventilation with RAW or CL changes Pressure support ventilation (PSV): variable patient tolerance and WOB Synchronized intermittent mandatory ventilation (SIMV): increased wob compared to AC
VOlume ventilation, pressure is variable, in pressure ventilation, volume is variable
With volume ventilation, volume is constant, if compliance decreases then pressure will increase with pressure ventiatlion, pressure is constant, if compliance decreases, then volume decreases
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Initiation of mechanical ventilation |
Primary goals of mechanical ventilation: (First goal is to decrease WOB) :Adequate oxygenation/ventilation :Reduced work of breathing: synchrony, in sync with vent :Avoidance of high peak pressure Initial seeings :FiO2 high then titrate down :Initial Vt should be: ::8 to 10 ml/kg ::ARDS consider tidal volumes between 5 to 8 ml/kg with increase in PEEP |
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Initiation of mechanical ventilation |
PEEP in diffuse lung injury and ARDS to support oxygenation and reduce FiO2 Avoid choosing ventilator settings that limit Te(expiratory time) that cause or worsen auto PEEP For decreasing oxygenation, inadequate ventilation, or increase PIPs due to intolerance of ventilator consider: (auto peep is internal peep that can slowly add up increasing pressures, can be very dangerous) :Sedation :Analgesia :Neuromuscular blockade |
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Trouble shooting the ventilator |
Common problems :High peak pressure :Patient with COPD :Ventilator Synchrony :ARDS (can develop or VAP) If PIP are increasing :Check compliance and RAW :If peak pressures are high and plateau pressures are low you have an obstruction (increased airway resistance) :If both peak pressures and plateau pressures(or static pressure) are high, then you have decreased lung compliance or stiff lung |
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Trouble shooting the ventilator |
High peak pressure differential: High peak preassures and low plateau pressures Mucous plug, bronchospasm, ET tube blockage or biting tube High peak pressure and high plateau pressures ARDS, pulmonary edema, pneumothorax, ET tube migration ot mainstem bronchus, pleural effusion. |
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Troubleshooting the ventilator |
COPD/asthma with decrease SPO2 and increase PaCO2 differential includes :Air trapping is of high concern leading to auto: PEEP :Management options include CaO2 X CO = DO2, normal is 1000 ml/ minute Decrease vent rate, decrease tidal volume, increase flowrate for faster delivery of Vt, adjust I:E ratio, increase sedation. The rate setting of the vent is the expiratory time, if you turn down the rate your E time goes up. |
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Troubleshooting the ventilator |
Increase in patient agitation and dissynchrony on the ventilator :Could be secondary to overall discomfort ::Increase sedation :Could be secondary to feelings of air hunger, options include ::increase Vt ::Increase flow rate ::Adjust I:E ratio Flow and volume are the two components of inspiratory time Rate is the one component of expiratory time |
