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Most initial mechanical ventilators were limited in modes. What types did most offer?
Control, Assist Control, IMV, SIMV
Newer mechanical ventilators offer what types of modes?
A/C, SIMV, CPAP (Spontaneous), Pressure Support
Initial mode is usually what kind of support? And in what mode?
Full support and in A/C and SIMV modes
Why is full support mode used?
The reason is to rest the patient's respiratory muscles and allow the ventilator to do all the work of breathing.
What type of targeted breaths are normally the initial breath type of choice: pressure or volume?
Volume in this part of the country
When using the SIMV, what should you set the RR as?
You should set the RR so that it meets or exceeds the patient's own RR or else they will have some WOB
What does Tidal Volume Control do?
It determines the tidal volume delivered to the patient. It is adjustable from 50-2000 ml
When is the Tidal Volume setting required (during what modes)?
It is required during A/C or SIMV volume targeted ventilation
If you increase the tidal volume, what happens to the VE? PaCO2?
An increase in TV = increase in VE = decrease in PaCO2
If you decrease the tidal volume, what happens to the VE? PaCO2?
A decrease in TV = decrease in VE = increase in PaCO2
What should you use for the inital tidal volume settings?
The initial settings should be 8 to 12 ml/kg ideal body weight (use 10 ml/kg for problems)
What tidal volume settings should you use for ARDS patients?
The settings should be around 4 ml/kg of IBW.
How would you get the range for TV?
Take the IBW and multiply it by 8 and 12 to get the low and high ranges.
It is an acute lung injury that is directly induced by positive pressure ventilation. Caused by opening alveoli too far and filling with fluid
What are the 5 ways that VILI can happen?
1. VAP - ventilator acquired pneumonia
What is VAP?
Pneumonia that occurs within 48 hours of being ventilated via a trach or ETT. Diagnosed by CXR AND sputum samples taken from trachea or bronchoscopy
What is barotrauma?
It is damage to the body tissue caused by a difference in pressure between an air space inside or beside the body and surrounding fluid. It affects 5-15% of ventilated patients.
How is pulmonary barotrauma caused?
Caused by the absolute pressures used to ventilate non-compliant lungs
When does barotrauma occur?
During: surgeries, Asthma, COPD, interstitial lung disease, pneumocystis carinii pneumonia
What is volutrauma?
Damage to the lung tissues cause by overinflation of alveoli. A pulmonary capillary is stressed by overdistention and ruptures alveolar, endothelial or basal membranes
What is atelectrauma?
It is the cyclic opening and collapse of alveoli during positive pressure ventilation increases stretch and shear forces resulting in lung injury and surfactant dysfunction.
What is biotrauma?
Lung injury caused by the release of proinflammatory mediators such as cytokines. Basically over-ventilation cause the body to activate it's inflammatory response system which ends up damaging the lungs, filling them with fluid.
What is the respiratory rate control?
The control that determines the number of mechanical breaths delivered by the ventilator per minute
When is the respiratory rate set?
Only set when using a mode of ventilation that delivers controlled (machine) breaths - pressure or volume ventilation
What initial settings would you use for respiratory rate?
You would use 8-12 bpm. Some patients may require higher (12-18)
What would happen to the VE & PaCO2 if you decrease the RR?
A decrease in RR = decrease in VE = increase in PaCO2
What would happen to the VE & PaCO2 if you increase the RR?
An increase in RR = increase in VE = decrease in PaCO2
What is the Total Cycle Time?
It is the total amount of time for an inspiration and expiration to occur.
How would you find out the frequency (how many cycles occur in a minute)?
Take the cycle time and divide it into 60 seconds.
f = 60 / Tct
What is a sensitivity control?
It determines the amount of patient effort that is required to initiate or trigger a mechanically supported breath.
Historically, what was the sensitivity control?
It was a pressure trigger with the patient required to produce enough negative pressure to meet the setting and trigger the breath.
What does flow sensitivity provide?
It provides a continuous flow through the circuit and the ventilator "senses" when the flow drops to a specified level and a mechanical breath is initiated.
What should the flow sensitivity be set to?
There is no standard, but continuous flow should usually be at least 4 or 5 LPM w/ a trigger flow of 1 to 2 LPM
What is the Peak flow control and what does it do?
It determines the speed at which the mechanical breath is delivered to the patient. It is how fast or how slow the breath is delivered.
If the flowrate is increased, what happens to the PIP?
It increases the PIP and the breath is delivered faster therefore decreased inspiratory time.
If the flowrate is decreased, what happens to the PIP?
It decreases the PIP and the breath is delivered slower, therefore increasing the inspiratory time.
You want to achieve an inspiratory time of what with an I:E ratio of what?
Inspiratory time of 0.8-1.2 seconds with a ratio of 1:4, but no less than 1:2.
Why can't peak flowrate be set on pressure ventilation?
It cannot be set because flowrates vary in pressure ventilation based on inspiratory time, set presure, lung compliance and patient demand.
What happens if you are unable to maintain an I:E ratio of 1:1 or more?
It iwll result in an inverse ratio situation, aka a longer inspiration time than expiration. It will also result in air-trapping, increased pressures, decreased venous return and higher risk of VILI.
What is the normal I:E ratio?
It is 1:2 or better (usually 1:4). If it is 1:2, that means that expiration is twice as long as the inspiration.
What does a ratio of 1:1 mean?
It indicates air trapping & auto-peep due to insufficient time for exhalation
How is the I:E ratio determined? Name 3 ways.
1. Tidal Volume Control - Increasing volume increases I-time; decreasing volume decreases I-time
2. Respiratory Rate Control - Increasing rate decreases E-time; Decreasing rate increases E-time
3. Peak Flow Control - Increasing flowrate decreases I-time (indicated when TV or RR is increased); Decreasing flowrate increases I-time (indicated when TV or RR is decreased)
What is a square wave?
It provides constant flow at a selected value; the average flowrate throughout the breath is highest using this pattern which may cause more shearing injury to the lung.
What is an ascending ramp flow pattern?
It provides progressive increase in flow which can be uncomfortable for patients, especially those who are air hungry.
What is a sine wave flow pattern?
It may provide more even distribution of gas in the lungs than the flow of constant flow. It is more comfortable than square wave pattern by low initial flow may still leave patient's wanting more flow at the beginning of inspiration.
What is a descending ramp flow pattern?
Provides high flow at the beginning of breath which results in lower WOB and lower flow at the end of the breath when the lungs are filling up and high flow is not needed. Provides the greatest benefits for the most patients.
What does the oxygen control do?
It determines the oxygen percent delivered and is adjustable from 21% to 100%
Oxygen should be decreased to 50% or below to maintain a PaO2 of what?
80-100 mmHg or for COPDers (55-65 mmHg)
What is PEEP control?
It is used to maintain positive pressure in the airway following a ventilator breath - improves oxygenation.
The initial settings for PEEP are usually what?
From 0 to 5. Many physicians order +5 of PEEP to mimic physiological PEEP
What is inspiratory hold control?
AKA "Inflation Hold" or "Inspiratory Pause"; it keeps the exhalation valve closed causing the ventilator breath to be held in the lungs for a preset time.
What should the sigh volume be set at?
1.5 to 2 times the set tidal volume and the rate should be set at 6 to 12 sighs/hour
How do you determine how much PIP to use in Pressure-targeted Ventilation? (2 methods)
1. Ventilate the patient w/ volume ventilation at desired TV level and obtain the Plateau pressure. Switch to Pressure ventilation and use a set inspiratory pressure that is equal to the measured plateau pressure.
2. Start with a low PIP (10-15) and observe TV measurement. Increase PIP as necessary to obtain desired TV.
The shorter the inspiratory time...
The faster the gas will fill the patient's lungs and the longer the expiratory time.
The longer the inspiratory time...
The slower the gas fills the patient's lungs and the shorter the expiratory time.
What can long inspiratory times lead to?
Lead to improved oxygenation but can also cause air trapping.
What can activate the high pressure alarm?
1. Increasing airway resistance
2. Decreasing lung compliance
What happens when the pressure limit is reached?
The remaining volume is released before being delivered and the patient does not receive the full volume from the ventilator.
What can activate the low pressure alarm?
A leak in the system or when the tubing becomes disconnected.
How is the low tidal volume alarm set off?
When the tidal volume is not delivered. Could be caused by a leak in the system or when the tubing becomes disconnected.
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