Vent Management Flashcards

1
Q

Normal I:E ratio (in a healthy, non-ventilated person) is what?

A

1:2

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2
Q

How do you change I:E ratio?

A

Change the inspiratory time

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3
Q

Give Sarah Crager’s breakdown of the ventilation display.

A

Top bar: “What is actually happening”

Bottom bar: “What I told the machine to do”

Middle section: “How does what I set lead to what is happening.”

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4
Q

What is Vtot?

A

Total minute ventilation calculated by measured Vte (end tidal volume returned by exhalation) by actual RR

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5
Q

Ventilators usually alarm based on what value?

A

PIP going above set threshold (usually 30)

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6
Q

What does the peak inspiratory pressure mean?

A

It is the highest pressure in the airway – from the ETT to the alveoli

PIP is less helpful than plateau pressure, because you don’t care if the ETT encounters high pressures, but you do care if the alveoli see high pressures.

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7
Q

What might be happening if the end-tidal volume is less than your set tidal volume?

A

In a pressure-regulated volume control mode (PRVC), the ventilator will cut off the volume delivered if the peak-inspiratory pressure (PIP) is maxed out.

When this happens, check a plateau pressure. This will let you know if you can safely set the PIP threshold higher.

Also, think about what else you could do to reduce obstructive physiology – such as suctioning airway mucus or giving bronchodilators.

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8
Q

What two parameters are the key to lung-protective ventilation?

A

Low tidal volume (6-8 mL/kg)
High PEEP (whatever value in the range 5-20 cm H2O leads to low FiO2)

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9
Q

What should the goal plateau pressure be?

A

Less than 30 cm H2O

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10
Q

What can cause a person who was previously oxygenating well on a vent to become hypoxemic after they were temporarily disconnected?

A

De-recruitment of alveoli

When the vent is disconnected, the airway pressure drops to zero. If they had edema/ARDS and it took a while to recruit their alveoli, then you may have lost the work you did.

If a person demonstrates that they de-recruit when disconnected, you can clamp the tube prior to disconnecting. Use a clamp without teeth that may cut the plastic.

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11
Q

In a person with no prior blood gases documented, how can you calculate their baseline pCO2?

A

For every 4 mmol/L HCO3 above normal, the pCO2 should be 10 mm Hg above normal.

So if a person’s baseline HCO3 is 36, then their baseline pCO2 is likely 70 mm Hg.
36 - 24 = 12 mmol/L above normal.
12 / 4 is 3
3x10 = 30 mm Hg above normal
30 + 40 mm Hg above normal = 70 mm Hg

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12
Q

If a person with COPD is on a ventilator with appropriate settings (e.g., I:E 1:4, RR 10, Tv 8 mL/kg, PEEP 5) and they are still breath stacking, what might you need to do?

A

Try to increase PEEP.

This is counterintuitive because PEEP is usually a problem in COPD. However, those with COPD have floppy airways

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13
Q

What are the two ways that hyperoxia leads to hypercarbia in COPD patients receiving supplemental O2?

A

In a spontaneously breathing person, supplemental O2 removes their hypoxic respiratory drive which decreases their respiratory rate. Hypoventilation thus leads to hypercarbia.

In a ventilated person, hyperoxia leads to impaired V/Q mismatch. In a person with COPD, the lungs adapt by shunting blood away from severely damaged alveoli. Adding excess oxygen causes the blood vessels that were previously constricted to dilate. Blood then shunts to damaged alveoli that are not ventilating and away from alveoli that are ventilating.

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14
Q

What things can you try to fix vent dyssynchrony (other than paralyzing them or sedating more)?

A

Put them in pressure support mode to see how they’re breathing – what RR, what volumes, what wave form

Speed up inspiratory time. Slow inspiratory times can be a source of discomfort.

Increase minute ventilation.

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15
Q

_________________ is referred to as “open-lung ventilation” because it keeps the airways open.

A

APRV

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