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S1 > Ventilatory Terminology/formulas > Flashcards

Ventilatory Terminology/formulas Flashcards

1
Q

Define “compliance” , what are the two subsets of it.

A

The extensibility of the lungs and chest wall.

-dynamic (measured during breathing) and Static (change in volume for any given applied pressure)

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2
Q

Define “flow”

A

Volume moving across time

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3
Q

Define “pressure”

A

Positive pressure to assist/ push a breath into the lungs

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4
Q

Define “Dead space”

A

Any area of lung that is ventilated but does not participate in gas exchange.

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5
Q

Define “shunt”

A

Area of lunch that receives blood but is not ventilated

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6
Q

Define “PEEP”

A

Positive end expiratory pressure

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7
Q

Define “auto-peep”

A

PEEP cause by progressive accumulation of air (air trapping) due to incomplete expiration prior to inhalation at the next breath

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8
Q

Define “transpulmonary peep”

A

Pressure required to breathe in, generated by the gradient across the respiratory system.

(Useful to set peep)

Formula:

airway pressure-esophageal pressure

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9
Q

Define “bias flow”

A

Continuous backflow of gas within the vent circuit responsible for replenishing oxygen and remaining CO2 from the patient circuit

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10
Q

Define “resistance “

A

The opposition to airflow in the patient’s respiratory system

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11
Q

Define “plateau pressure”

A

The pressure applied to the alveoli and small airways by a mechanical ventilator during the end of an inspiratory pause.

Formula

Pplat=(VTe/Cstat) + PEEP

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12
Q

Define driving pressure

A

The measure of stress on the respiratory system between the end of inhalation and the end of exhalation.

Formula:

P=Vt/cstat

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13
Q

Define “static compliance” (Cstat)

A

Static compliance is the measurement of pulmonary compliance when there is no airflow.

Cstat= Vt (Pplat-PEEP)

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14
Q

Define a “truncated” waveform

A

A distorted version of an original waveform that has been cut at points where the signal amplitude exceeds the measurement limits of the sensor

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15
Q

Define a non-truncated waveform

A

A waveform that is original and not distorted

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16
Q

Define critical airway opening pressure

A

Elastic pressure at which the gas volume delivered to a patient is 4ml greater than the volume compressed in an occluded circuit.

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17
Q

Define VTe

A

Expired tidal volume

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18
Q

Define Vt

A

Tidal volume

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19
Q

Define Te

A

Expiratory time

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20
Q

Define Ti

A

Inspiratory time

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21
Q

What causes the “high pressure” alarm to trigger

A

The ventilator pressure has reached or exceeded the set limit.

Causes:
-tubing is kinked
-water in the circuit
-increased mucous secretions
-bronchospasm
-coughing, gagging, fighting (undersedated)

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22
Q

What causes the Low Vt alarm to activate

A

Inadequate tidal volume

Causes:
-circuit leaks
-decreased compliance
-need for suctioning
-tube displacement

23
Q

What causes the high rate alarm to sound

A

The rr has exceeded the set limit

Causes
-agitation
-inadequate sedation
-pain/physiological process

24
Q

Define the Low Vmin alarm and what are ways to trouble shoot it

A

Triggered whenever the expiratory volume falls below the present threshold

Checks:
-leaks, disconnections, pilot balloon, tube verification, tube cuff and vent settings

25
Q

Define the DOPES pneumonic

A

Displacement
Obstruction
Pneumothorax
Equipment failure
Stacked breaths

26
Q

What is asynchrony

A

Occurs when patient breathes do not match ventilator controlled breaths

27
Q

What are 7 ventilator related causes of asynchrony

A
  1. Inappropriate sensitivity setting
  2. Prolonged I-time
  3. I-time too short
  4. PCV/PSV applied pressure too high, rise time too short
  5. Muscle effort resulting from mechanical inflation
  6. I-time too long relative to the patients I-time
  7. VC flow setting is too low or too high
28
Q

What are 4 patient causes of asynchrony

A
  1. Respiratory muscle weakness or auto-peep
  2. Transmission of pressure or flow oscillations secondary to cardiac activity
  3. Restrictive lung mechanics in PSV (fibrosis etc)
  4. Excessive ventilator demand, increased neural drive
29
Q

What is the equation for Pplat?

A

Pplat= Vt/Cstat + PEEP

30
Q

What is the equation to determine driving pressure?

A

DP=Vt/Cstat

31
Q

What is the equation to determine minute ventilation? Vmin

A

Vmin=RR x Vt

32
Q

What is the equation to determine the I:E ratio?

A

I:E =rr x i-time

33
Q

Define i-time

A

the amount of air in and out in one respiratory cycle

34
Q

What is the expired tidal volume representative of?

A

Expired tidal volume, the amount of gas leaving the lungs at the end of exhalation. May not necessarily match Vt

35
Q

Define Peak inspiratory pressure

A

The highest level of pressure at any given delivery of gas. Primarily altered by airway resistance.

36
Q

Where is PIP mostly felt within the patient

A

The upper airways.

37
Q

What are three approaches to addressing patient assynchrony?

A
  1. Adjust the ventilator
  2. Revisit sedation
  3. Paralyze
38
Q

Define Flow (VCalc)

A

Flow is the speed of airflow during inhalation, measured in L/min

39
Q

What primarily influences flow?

A

I-TIME primarily influences flow

40
Q

Measured at end of inspiration. This pressure is being felt by the alveoli. It is the pressure applied to the small airways and alveoli during an inspiratory pause, or no flow state, on the ventilator.

What is this reffering to?

A

Plateau pressures. Pplat=Vt/Cstat

41
Q

What is the acceptable limit for Pplat?

A

30cmh20

42
Q

What are three ways to reduce high Pplat?

A
  1. Reduce Vt
  2. Increase compliance (recruitment manouvers, proning)
  3. Decrease PEEP
43
Q

How does an esophageal balloon catheter aid us in dealing with high Pplats?

A

Esophageal balloon catheters give us the TPp, by comparing Pplat-Pes we seperate the lungs from the chest wall. We can see exaclty what is going on in the lungs without external influence—this may allow us to tolerate higher than normal Pplats.

44
Q

What are three ways to identify Pplat

A
  1. Formula
  2. No flow state
  3. Ventilator screen
45
Q

In volume control/assist mode, what are the six constants and 1 variable

A

Volume, RR, i-time, flow, fio2, sensitivity. The variable is pressure.

46
Q

In VC/A what components result in triggering of the vent?

A

Time, Flow,

47
Q

How is volume control mode cycled?

A

I-time, Volume target.

48
Q

What are the 4 constants, and two variables in PCV

A

Constants: pressure, rr, i-time, fio2
Variable: Flow, Vt

49
Q

How is PCV triggered?

A

I-time, flow triggered (depends on sensitivity levels)

50
Q

How is PCV cycled?

A

Time, Flow displacment in Assist.

51
Q

In pressure control, what will increasing i-time and pressure result in?

A

Increased volume.

52
Q

Define SCMV+

A

SCMV+ is a volume targeted, pressure regulated mode of ventilation. NOT Volume mode. Pressure will ramp up in increments of 2 until Vt is achieved.

53
Q

What are the four points of focus for interpreting a pressure volume loop?

A

-zone of resistance
-Critical airway opening pressure
-zone of optimal compliance
-Zone of overdistention

54
Q

For setting alarm parameters on the ventilator. What are the ranges for the alarms we set?

A

Pressure: 20 above, 10 below
Vmin: 1.5 above, 1.5 below
RR: 8-10 above, 12-16 below
Vt: 6cc/kg lower limit, 8cc/kg upper.

S1 (8 decks)

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