10 Maxims Fro Modes of Mechanical Ventilation

Question 1

A breath is a cycle of what

Answer 1

A breath is one cycleof positive flow (inspiration) and negative flow (expiration) defined in terms of the flow-time curve

Question 2

Inspiratory Time Definition

Answer 2

Inspiratory time is defined as the period from the start of positive flow to the start of negative flow

Question 3

Expiratory Time Definition

Answer 3

Expiratory time is defined as the period from the start of expiratory flow to the start of inspiratory flow

Question 4

When is a breath considered to be assisted

Answer 4

An assisted breath is one for which the ventilator does some or all of the work of breathing

For constant flow inflation, work is defined as inspiratory pressure multiplied by tidal volume

Question 5

A ventilator will assist breathing using either

Answer 5

Pressure Control

Volume Control

This will be based on the equation of motion for the respirtory system

Question 6

Equation of Motion for the Respiratory System

Answer 6

P_vent+ P_mus= Elastance x Volume + Resistance x Flow

Supposing that expiration occurs passively, as it does in the majority of cases, Pmusc and Pvent are absent and the equation of motion therefore becomes:

-Resistance x Flow = Elastance x Volume

The minus sign at the left of the equation indicates the negative direction of the expiratory flow and suggests that during passive expiration the flow is generated by the energy stored in the elastic component during inspiration.

Question 7

Pressure Control in Regards to Equation of Motion

Answer 7

-Resistance x Flow = Elastance x Volume

Pressure control (PC) means that inspiratory pressure is present as either a constant value or it is proportional to the patient’s inspiratory effort

Volume and flow change will change with elastance and resistance

Question 8

Volume Control in Regards to Equation of Motion

Answer 8

-Resistance x Flow = Elastance x Volume

Volume control (VC) means that both volume and flow are preset prior to inspiration. In other words, pressure changes with changes in elastance and resistance.

Question 9

Breaths are classified according to

Answer 9

The trigger which is what starts inspiration

The cycle which is what ends inspiration

Question 10

The Trigger and Cycle Varible Can Be Either

Answer 10

Patient Initiated or Machine Initiated

Question 11

Machine Triggered Breath

Answer 11

Inspiration is started due to a signal from the Ventilator which is independant of the patient

Question 12

Patient Triggered Breath

Answer 12

Inspiration is started due to a signal from the patient which is independant of the ventilator

Question 13

Patient Cycled Breath

Answer 13

Patient cycling means ending inspiratory time based on signals representing the patient determined components of the equation of motion, (i.e, elastance or resistance and including effects due to inspiratory effort).

Question 14

Flow Cycline

Answer 14

Form of pt cycling

When the rate of flow decreases to a pre set threshold which is determined through pt lug mechanics

Question 15

Machine Cycling

Answer 15

Inspiration is ended due to factors determined by the ventilator

Question 16

Based on the triggering and cycling event breaths are classified as

Answer 16

Sponatneous or Manadatory

Question 17

Spontaneous Breaths

Answer 17

A spontaneous breath is a breath for which the patient both triggers and cycles the breath

A spontaneous breath may occur during a mandatory breath (e.g. Airway Pressure Release Ventilation)

A spontaneous breath may be assisted or unassisted.

Question 18

Mandatory Breaths

Answer 18

A mandatory breath is a breath for which the machine triggers and/or cycles the breath
A mandatory breath can occur during a spontaneous breath (e.g., High Frequency Jet Ventilation)

A mandatory breath is, by definition, assisted.

Question 19

Basic Breath Sequences

Answer 19

Continuous mandatory Ventilation (CMV)

Intermittent Mandatory Ventilation (IMV

Continuous Spontaneously Ventilation (CSV)

Question 20

Continuous Mandatory Ventilation

Answer 20

Spontaneous breaths are not allowed between mandatory breaths

Question 21

Intermittent Mandatory Ventilation

Answer 21

Spontaneous breaths may occur between mandatory breaths

Question 22

Continuous Spontaneous Ventilation

Answer 22

All breaths are spontaneous

Question 23

5 Basic Ventilatory Patterns

Answer 23

VC-CMV,

VC-IMV,

PC-CMV,

PC IMV,

PC-CSV

Question 24

VC-CSV

Answer 24

The combination VC-CSV is not possible because volume control implies machine cycling and machine cycling makes every breath mandatory, not spontaneous.

Question 25

TC-IMV

Answer 25

possible but rare

Question 26

Within each Ventilatory Pattern there are several types that can be distinguished by their target schemes.

Answer 26

Set-Point

Dual

Bio-Variable

Servo

Adaptive

Optimal, Intelligent

Question 27

Targeting Scheme

Answer 27

A targeting scheme is a description of how the ventilator achieves preset targets.

A target is a predetermined goal of ventilator output.

Question 28

Within Breath Targets

Answer 28

include inspiratory flow or pressure and rise time

tidal volume

constant of proportionality between inspiratory pressure

patient effort

Question 29

Set Point Targeting

Answer 29

Targeting scheme where the operator sets all the parameters or either volume or pressure

Question 30

Dual Control Targeting Scheme

Answer 30

A targeting scheme that allows the ventilator to switch between volume control and pressure control during a single inspiration (mid breath)

Ex. VAPS

Question 31

Bio-Variable Targeting Scheme

Answer 31

A targeting scheme that allows the ventilator to automatically set the inspiratory pressure or tidal volume randomly to mimic the variability observed during normal breathing

Will try to mimic variability in human breathing by varying Vt breath to breath

Question 32

Servo Targeting Scheme

Answer 32

A targeting scheme for which inspiratory pressure is proportional to inspiratory effort

More effort leads to more support

Ex. Tube Compensation

Question 33

Adaptive Targeting Scheme

Answer 33

A targeting scheme that allows the ventilator to automatically set one target (e.g. pressure within a breath) to achieve another target (e.g. average tidal volume over several breaths)

Ex. Volume support, PAV, NAVA

Question 34

Optimal Targeting Scheme

Answer 34

A targeting scheme that automatically adjusts the targets of the ventilatory pattern to either minimize or maximize some overall performance characteristic (e.g. minimize the work rate done by the ventilatory pattern)

Tries to achieve optimal breathing based WOB curves

Ex. ASV

Question 35

Intelligent Targeting Scheme

Answer 35

A targeting scheme that uses artificial intelligence programs such as fuzzy logic, rule based expert systems, and artificial neural networks.

Auto adjust settings based on monitored parameters such as etCO2 and SpO2

Smart Care, Intellivent

Question 36

A Mode Of Ventilation is Classified Based on What

Answer 36

1. Control Varible (pressure or volume) for the primary breath
2. Breath Sequence (CMV, IMV, CSV)
3. Primary Breath Targeting Scheme (for CMV or CSV)
4. Secondary Breath Targeting Scheme (IMV)

Question 37

The Primary Breath

Answer 37

The “primary breath” is either the only breath there is (mandatory for CMV and spontaneous for CSV) or it is the mandatory breath in IMV.