Mod 5 Vent Variables Flashcards by Derrick Chuong

how do you determine if you match a patients O2 needs/requirements?

Good CNS function

good perfusion

etc. indeterminable without a mixed venous pressure/sample to get a better idea at the hemoglobin

i.e good LOC

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What are the Vent. Mode basics?

volume control

Pressure control

pressure support

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which pressure is maintain in all vent. modes?

PEEP (range 4-6;but set 5)

Keeps interalveolar airways open

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What is oxygenation and ventilation controlled with?

Oxygenation: FiO2 and MAP
(hypoxic)

Ventilation: RR
(acidotic)

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Vital capacity is a good measure of what?

our ability to cough (and help clear secretions

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What is the purpose of ventilation?

-Supporting/manipulating gas exchange:

-Increase lung volume

-Reduce/manipulate WOB

-Minimize cardiovascular impairment

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What are 2 types of respiratory failure?

Hypoxemic respiratory failure

Hypecapnic respiratory failure

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What value is affected to be classified as hypoxemic respiratory failure?

PaO2 < 60mmHg on room air.

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What values change to be classified as Hypercapnic respiratory failure?

PaCO2 > 45 mmHg

pH < 7.35

Also known as respiratory acidosis

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when hypoxemic respiratory failure results in a normal (A-a) gradient; what is the usual cause?

decreased PiO2 or Hypoventilation

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An increased (A-a) gradient will result when the hypoxemia is due to which defects/conditions?

True shunt

V/Q mismatch

Diffusion defects

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What are classic indications for mechanical ventilation? (4)

Apnea
Acute ventilatory failure
Impending ventilatory failure
Severe refractory hypoxemia

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What are signs of impending ventilatory failure?

WOB

Muscle strength and lung expansion critical numbers

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What are common causes of hypoxemic failure?

V/Q mismatch

shunt

alveolar hypoventilation

diffusion impairment

decreased inspired FiO2

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Causes of Apnea

Arrests

sedation (o.d)

paralytic drugs

high c-spine injury

head injury/trauma

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Signs of impending vent. failure?

air hunger

tachypneic

diaphoretic

WOB

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Neuromuscular failure

guilluain-barre

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refractory failure can be inferred by what factors?

an increase in PaO2 of less than 10mmHg after an FiO2 increase of 0.20 (or more)

PaO2 < 60 of an FiO2 of > 0.40

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slide 7 (mod 5 - A)

edit

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Critical numbers indicating inadequate alveolar ventilation

(i.e needs mech. ventilation)

PaCO2 > 55mmHg

pH < 7.25 (or 7.20)

BOTH must be met to indicate mechanical ventilatory support.

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mechanisms for increased PaCO2 when there is inadequate alveolar ventilation.

Increased deadspace

Increased CO2 production

Decreased alveolar ventilation (Va)

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Critical numbers indicating inadequate lung expansion

(i.e needs mech. ventilation)

Tidal volume < 5 mL/kg

Respiratory rate > 35 bpm

Vital capacity < 10 mL/kg

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Small volumes result in inadequate lung expansion; what are they complications and predicted outcomes if this is the case?

Complications: atelecasis and impaired gas exchange

result in increased RR to maintain Ve (minute ventilation)

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Higher respiratory rates correspond to what?

lower volumes.

Can lead to respiratory muscle fatigue

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what is vital capacity?

The volume of air exhaled after a maximal inspiration

why is vital capacity a important value when determining whether or not a patient needs mechanical ventilation?

Vital capacity indicates both muscle strength and lung expansion ability; TLDR; reflects the ability to cough and clear the airway.

How much vital capacity is needed for an adequate cough?

2 x tidal volume (Vt)

How do you measure vital capacity?

typically with a wrights (turbine) or bedside spirometer.

which patients would test vital capacity for?

those with progressive muscle weakness. (ALS, GBS, MG etc.)

Critical numbers that indicate inadequate muscle strength (i.e needs mech. ventilation)

-Max inspiratory pressure (MIP) greater than or equal to -20 cmH2O -Max expiratory pressure (MEP) less than 40 cmH2O -vital capacity < 10 mL/kg -max voluntary ventilation < (2 x Ve)

Normal tidal volume?

5 - 8 mL/kg

Normal vital capacity?

65 - 75 mL/kg

Normal max inspiratory pressure (MIP) what is it a measure of?

-80 to -100 cmH2O Measures patients muscle strength

How do you measure max inspiratory pressure (MIP)? who would it be done for?

Uses nose plugs; a pressure gauge, and a one-way valve that allows for exhalation only. patients with progressive neuromuscular disorders (i.e MG, GBS, ALS)

Normal Max expiratory pressure (MEP)

Normal > 100cmH2O

How do you calculate minute ventilation (MV) and what is a normal range?

MV = RR x Vt Normal = 5-6 lpm

Critical value for WOB (i.e needs mech. ventilation)

Minute ventilation [MV (or Ve)] > 10 LPM Deadspace to tidal volume ratio (Vd/Vt) > 0.60

what are complications with minute ventilation in relation to WOB? *edit*

Ve needed to maintain a stable PaCO2 may become so high that it can’t be reached by the patient. at > 10 LPM; increased probability of respriatory failure developing 2 degrees to muscle fatigue

Normal deadspace to tidal volume ratio (Vd/Vt)

0.25 - 0.40 (25 - 40 %)

It takes work to move the air in and out of deadspace. Why does Deadspace increases WOB

to maintain alveolar ventilation; which is also increased

For a given PaCO2, what variables increase/decrease to maintain PaCO2?

Deadspace (Vd) and minute ventilation (Ve)

M5 slide 17 (left off) *edit*

What is continuous mandatory ventilation (CMV)?

Every breath is controlled by the ventilator -may be vent. initiated (mandatory) -may be patient initiated (assisted) -vent. does all the WOB after initiated. FULL vent. support.

Define intermittent mandatory ventilation (IMV)

Goal is to only deliver set # of mandatory breaths -all breaths delivered above set rate are spontaneous

what is continuous spontaneous ventilation (CSV)?

breaths may be supported or unsupported by the ventilator

What is the main difference in trigger variable for assisted vs. mandatory breaths?

Assisted breath: patient begins inspiration but the ventilator controls inspiratory phase and ends inspiration. Mandatory breaths are triggered only by time.

What are spontaneous breaths?

breaths that are triggered and cycled by the patient. it can be supported or non supported

Non-supported spontaneous breaths: can be defined as?

Breaths that are triggered, limited, and cycled by the patient (vent does nothing) The vent controls the baseline only; all phases except the baseline are controlled by the patient

Define supported spontaneous breaths

Breaths that are triggered and cycled by the patient, but limit and baseline are controlled by the vent. Amount of Vent support determines WOB the patient must do

Ventilators: control system - phase variables

Triggers: Time, Flow, Pressure Limit: Pressure, Volume, Flow Cycle: pressure, volume, flow, time Baseline

Ventilators: What is a Time triggered variable?

Controlled or mandatory breaths. Breath is delivered after an amount of time has passed. -breath is mandatory because vents start it. *need a RR to get a time trigger*

Ventilators : A/C refers to what?

breaths are either assisted or controlled. -patient triggered or time triggered.

What is an advantage of assist/control (CMV) ventilation?

If patient doesn’t trigger the breath, there is backup of time triggered breaths.

Ventilators: What does max sensitivity mean?

Ease for patient to trigger a breath.

Ventilators :What is a limit variable?

a variable that can reach/maintain a parameter before inspiration ends but does not terminate inspiration

What are the 3 limit variables for Ventilators?

Pressure Volume Flow

Ventilators: 2 ways to Pressure limit inspiration?

When looking at a Ventilator, what are the 3 graphs displaying?

In descending order: Pressure (cmH2O) Flow (L/m) Volume (mL)

What is PEEP?

Positive End-Expiratory Pressure: Keeps airway pressure above atmospheric throughout breathing cycle.

What are the advantages of PEEP?

PEEP maintains a patients FRC and can help improve oxygenation. -referred to as CPAP when using w/spontaneous breathes

What is VC-CMV? What is the Trigger, limit, cycle, and baseline? *edit* add slide 56

Volume controlled; continuous mechanical ventilation

How could you go about increasing lung volumes on a ventilator?

End-inspiration End-expiration FRC

What affects can mechanical ventilation have on cardiac function?

Can reduce myocardial demand secondary to hypoxemia and increased WOB

what factors increase PIP?

Anything that increases Pr or Pc

Does Pplat have a direct or indirect relationship with Volume & PEEP?

Direct

Does Pplat have a direct or indirect relationship with compliance?

Inverse

Variable relationships: If you have [I] time and Vt; what can you calculate?

Flow [I]time = Vt / Flow (Litres per second)

Variable relationships: What variable does RR affect?

Expiration time; Explanation: TCT = 60/RR --> TCT = I + E TCT = Time cycled between breaths

What is Flow?

How fast gas/fluids are moving Measurement: Liters per minute

Positive airway devices: how do you increase pressure?

Increase flow = Increase pressure

What happens to CO2 when RR increases?

It decreases; you blow off CO2

When would you not want to increase RR given a high CO2?

When pH is still normal; Pt could have a abnormal normal chronic condition; i.e emphysema or COPD are compensated by HCO3 so its normal.

In volume control; how would you decrease inspiratory time?

Increasing flow; air is delivered faster.

Will a decreased PiO2 result in a decreased or increased [A-a] gradient?

normal A-a

When would hypoxemic resp. failure result in a normal A-a gradient?

When it is due to a decreased PiO2 and Hypoventilation

Hypoxemic resp. failure will result in a high or low PaO2?

Low

Hypoxemic resp. failure will result in a high or low PaCO3?q

Normal to Low

Hypoxemic resp. failure will result in a high or low P(A-a)O2?

high or normal (normal if decreased PiO2 or hypoventilation)

Hypercapnic resp. failure will result in a low or high PaO2?

Low

Hypercapnic resp. failure will result in a low or high PaCO2?

High

Hypercapnic resp. failure will result in a high or low P(A-a)O2?

Normal

Combined Type I and II resp. failure result in a high or low PaO2?

Low

Combined Type I and II resp. failure result in a high or low PaCO2

High

Combined Type I and II resp. failure result in a high or low P(A-a)O2?

High

When the vital capacity [VC] is below 15-20, what does it indicate?

A lack of muscle strength and lung expansion to produce a adequate cough.

How do you know if someone doesn't have an adequate cough based on vital capacity?

VC < 15-20 mL/kg VC of 2 x Vt is needed for an adequate cough

A normal MV is what? and when are we concenred?

Normal = 5-6 Lpm Critical > 10LPM

What is a normal MIP? and when are we concerned?

-80 to -100 cmH2O Critical >= -20 cmH2O

What does MIP measure?

Pt's muscle strength

What is a normal MEP? and when are we concerned?

Normal > 100 cmH2O Critical < 40cmH2O

Any circuit distal to the WYE is added what?

Mech. deadspace

What is the point of heated wires in vent. circuits? (2)

Prevents rainout Prevent condensation

Why are water traps on some ventilators?

To collect rainout

True or False: Frequently changing the circuit is a good way to prevent contamination and decrease the risk of vat?

False. There is an increased risk of VAP with frequnet circuit changes (no more than q7d)

Mod 5 Vent Variables Flashcards

(94 cards)