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44 Cards in this Set

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What is compliance?
The ratio of change in volume to change in pressure.
What is the calculation for Dynamic compliance?
TV / (Peak Pressure-PEEP)
What is the calculation for Static compliance?
TV / (Plateau Pressure-PEEP)

What are the normal ranges for adults and children?
Adults: 35-100 mL/cmH20

Children: >15 mL/cmH20
What is Elastance?
A measure of the tendency of a hollow organ to recoil toward its original dimensions upon removal of a distending or compressing force.

What is it reciprocal to?
Compliance
What is Resistance?
Loss of pressure at the end of a tube when a fluid flows through it.
When it comes to resistance with the airway or mechanical resistance of the trach. tube or breathing system, what is a normal resistance level?
2-5 cm H20
If there is a decrease in the caliber of the airway, ETT, or breathing system, what happens to resistance?
It increases.

What are some real examples of instances when resistance would increase?
Bronchoconstriction, secretions, tumor, swelling, foreign body, kink in tracheal tube or dislodgement of tracheal tube, constriction or sharp bends in the breathing system.
Pressure drop can be calculated how?
Resistance x Flow rate

How would you calculate the resistance for this equation?
Peak - Plateau pressure
Plateau pressure is affected only by what?
Compliance
If TV and inspiratory flow stay the same but resistance increases, what happens to the difference between the peak and plateau pressures?
The difference between peak and plateau pressures INCREASES.
What can be done to keep TV constant when resistance increases?
Use an increased pressure or a longer flow for a longer time.

If this isn't done what will happen to the TV?
It will drop.
In terms of induction, what is V.1?
The volume exhaled in the first second; this is passive.

What is a normal V.1?
70%
If V.1 is less than 70%, what does this indicate?
Increased resistance or decreased compliance.
What is FEV1?
Active exhalation; not under anesthesia.

What is a normal FEV1?
More than 80%
A pressure-volume loop mainly measures what?
Compliance
In terms of controlled ventilation, what direction on the pressure-volume loop does inspiration and expiration follow?
A counterclockwise loop

When is it clockwise?
During spontaneous ventilation.
In a pressure-volume loop, what is measured on the horizontal axis?
Pressure
In a pressure-volume loop, what is measured on the vertical axis?
Volume
In a pressure-volume loop, what two things are represented at the highest point of the loop?
Tidal volume (read on the vertical axis) and beginning of expiration.
How can you tell there is PEEP involved in a pressure-volume loop?
The lowest point on the loop corresponds to a non-zero pressure on the horizontal axis.
In a pressure-volume loop, what does the area inside the loop correspond to?
Work of breathing
In a pressure-volume loop, what does the slope of the loop show?
Compliance

What does a loop that is more horizontal than the baseline loop indicate?
A more horizontal loop indicates that a high pressure is required to deliver a relatively low volume.
In a pressure-volume loop, what does a more vertical loop than its baseline loop indicate?
That a low pressure is needed to give a high volume (increased compliance)
What are some examples of factors that cause a decreased compliance in the lungs?
Air embolism, pneumothorax, obesity, curvature of the spine, prone position, narcotics, etc.
What are some factors that contribute to increased lung compliance?
PEEP and resolution of factors that decrease compliance.
How is increased resistance seen on a pressure-volume loop?
Higher pressures with the same or decreased tidal volume.

It will be a clockwise shifted loop with large internal area. Pressure falls rapidly at end-inspiration.
Flow-volume loops measure what specifically?
Resistance
On the horizontal axis of a flow-volume loop, what is measured?
Volume
On the vertical axis of a flow-volume loop, what is measured?
Flow
Where is the zero point for volume located on the flow-volume loop?
On the right of the horizontal axis.

What does the zero point correspond to?
Functional Residual Capacity
In a flow-volume loop, Inspiratory flow moves which way on the horizontal axis?
Lefward as volume increases and drops to zero at end-inspiration. (from its negative point)
At which point is tidal volume represented on a flow-volume loop?
When the volume drops to zero at end-inspiration.
On a flow-volume loop, inspiratory flow is plotted _____ the horizontal axis.
Below
On a flow-volume loop, expiratory flow is shown _______ the horizontal axis.
Above
What is the shape of the flow-volume loop determined by?
Passive lung deflation (this includes elastic properties of the lungs/chest wall and total resistance of the tubes)
A normal shape of a flow-volume loop is a flow rate that _______ rapidly in early _______, quickly reaches a peak, then slows and gradually returns to ______.
increases

expiration

zero
The shape of the expiratory portion of the flow-volume loop changes according to what?
Changes in Resistance
In a flow-volume loop, Increased resistance causes:
Decreased peak expiratory flow, decreased flow throughout exhalation, and possibly decreased TV
How does the shape of the flow-volume loop change in the instance of spontaneous ventilation instead of controlled?
The inspiration portion is more rounded instead of a straighter, steady inhalation.
What are some factors that could cause increased resistance?
Tracheal tube obstruction, bronchoconstriction, airway obstruction, tracheal tube too small
What happens to the inspiration portion of a pressure-volume loop when the patient has a spontaneous respiration?
There will be negative pressure
What does an open loop indicate?
Exhaled volume is less than inhaled volume
What are some negative factors that can cause an open loop?
Incorrect calibration, incomplete exhalation before the next inhalation (COPD, lung retraction), a leak distal to the sensor (partial disconnect, cuff leak, tension pneumo)

What else will a tension pneumo show?
Decreased compliance
What are some normal causes for an open loop?
An uncuffed ETT or use of LMA

Double lumen endobronchial tube (increased resistance)

Gas exchange imbalance (O2 uptake > CO2 excretion or induction where uptake of agent/N2O is high)