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
What is the adjustable rate on most standard adult ventilators?
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 level should the plateau pressure be maintained at if possible?
< 30 cmH2O
What would happen if the plateau is increased higher than 30?
There are increased mortality rates
What is the Total Cycle Time?
It is the total amount of time for an inspiration and expiration to occur.
What is the formula for Tct?
Tct = Ti + Te
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 pressure sensitivity level be set to?
-1 to -2 cmH2O
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.
How does adjusting the flowrate affect the PIP?
It alters it because of airway resistance.
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.
What are the adjustable ranges for Peak flow?
It can range from 20 to 120 LPM
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.
What are the initial settings for Peak flow? As in, what should you start the patient on?
When is the only time you can set peak flow?
During volume ventilation.
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 I:E ratio?
It is a comparison of the inspiratory time to the expiratory time.
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.
Should the inspiration exceed the expiration?
What does a ratio of 1:1 mean?
It indicates air trapping & auto-peep due to insufficient time for exhalation
What does an inverse ratio indicate?
It impedes venous return.
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%
What would you initially put the oxygen setting on?
100% until you obtain an ABG
Oxygen should be decreased to 50% or below to maintain a PaO2 of what?
80-100 mmHg or for COPDers (55-65 mmHg)
If you cannot maintain a PO2 of 50-60%, what should you do to improve oxygenation?
What is PEEP control?
It is used to maintain positive pressure in the airway following a ventilator breath - improves oxygenation.
PEEP is adjustable from what to what?
0 to 50.
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 is the inspiratory hold used for?
It is used to obtain a plateau pressure
Inspiratory hold control is adjustable from what to what?
0 to 2 seconds. It is normally set on 0
What is sigh control?
It is to mimic an actual sigh
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.
In pressure-targeted ventilation, what is set instead of Peak Flow?
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.