DR/ MAHMOUD EL

NAGGAR

Egyptian Board of NeonatologyJune 1, 2016

1

2. VENTILATORY MODES

Definition of Mechanical

Ventilation

June 1, 2016

2

Mechanical ventilation is the

movement of gas in and out of

the lung by an external source

(an automatic mechanical device)

connected directly to the patient.

Purpose of MV

June 1, 2016

3

Facilitate alveolar ventilation and carbon dioxide removal.

Provide adequate tissue oxygenation

Reduce the work of breathing

Relieve respiratory distress and Reverse respiratory muscle fatigue

Permit lung healing

Avoid complications

Mechanism of action of MV

Patient

lung

Expiration

Patient

lung

Inspiration

Expiratory valve

Leak

Continuous flowContinuous flow

spontaneo

us

Mechanism of action of MV5

Spontaneous Inspiration

Hera NICU 2016

Volume Change

Gas Flow

Pressure Difference

Mechanical Ventilation

Hera NICU 2016

Pressure Difference

Volume Change

Gas Flow Patient

lung

Inspiration

Basic design of ventilatory

circuit

Hera NICU 2016

Expiratory valve

Hera NICU 2016

Unique challenges during

neonatal ventilation

Children ≠ Small adult

Neonate ≠ Small child

10

Classification of Mechanical

ventilators

June 1, 2016

11

1- By power source:

a) Pneumatic

b) Electrical

2- By rate:

a) Conventional

b) High frequency

Classification of Mechanical

ventilators

June 1, 2016

12

3- By pressure relationship to the patient:

a) Negative

b) Positive

4- By cycling mode at termination of inspiration:

a) Volume cycling

b) Pressure cycling

c) Flow cycling

d) Time cycling

e) Mixed cycling

Classification of Mechanical

ventilators

June 1, 2016

13

5- Loop control of ventilator output:

a) Opened loop

b) Closed loop

Negative-pressure ventilators (iron lungs)

Hera NICU 2016

•Non-invasive ventilation first used in Boston Children’s Hospital in 1928

•Used extensively during polio outbreaks in 1940s – 1950s

Polio outbreaks

June 1, 2016

15

Iron lung polio ward at Rancho Los Amigos Hospital in 1953

Negative pressure

ventilation16

Recent –Ve pressure

ventilator

Hera NICU 2016

1st Positive pressure

ventilation

June 1, 2016

18

• Invasive positive pressure ventilation first used at Massachusetts General Hospital in 1955

• Now the modern standard of mechanical ventilation

Volume control Vs Pressure

control

June 1, 2016

19

Volume control is good and

bad

Guaranteed tidal volume, even with variable

compliance and resistance

Less atelectasis compared to pressure

control

Can cause excessive airway pressure

The limited flow available may not meet the

patient desired inspiratory flow rate –

asynchrony

Leaks leads to volume lossHera NICU 2016

Pressure control is good and

bad

Limit excessive airway pressure

Improve gas distribution

Less tidal volume as pulmonary mechanic

change

Potentially excessive VT as compliance

improves

Hera NICU 2016

Open Vs closed loop

ventilation

June 1, 2016

22

June 1, 2016

23

1- Set tidal volume

With

2- Safer pressure limit

Target of

neonatal

ventilation

Conventional Neonatal

Ventilators

June 1, 2016

24

Pressure limited

Time cycled

Continuous flow

ventilators

In all pressure controlled

ventilation modes

June 1, 2016

25

Tidal Volume supplied depend on:

1- PIP- PEEP2- Lung mechanics3- Respiratory drive

of the patient

Why volume control not

suitable of newborn?

June 1, 2016

26

Use of small number of tidal volumes

Leak around un-cuffed ET

True tidal volume is influenced by ventilator

circuit compliance

Comprisable volume of the circuit including the

humidifier, can affect the tidal volume

Breath Types during mechanical

ventilation Mandatory (controlled)

Ventilator does the work

Ventilator controls start and stop

Spontaneous Patient takes on work

Patient controls start and stop

Assisted Patients triggers the breath

The ventilator delivers the breath as per control variable

Supported Patients triggers the breath

Ventilator delivers pressure support

Breath cycles at set flow

Hera NICU 2016

Hera NICU 2016

June 1, 2016

29

Ideal ventilator design

June 1, 2016

30

Achieve all the important goals of mechanical

ventilator

Provide a variety of modes that can ventilate

even the most challenging lung diseases.

Has monitoring capabilities to adequately

assess the ventilator and patient performance.

Has safety features and alarms that over lung

protective strategies.

Neonatal ventilator.

Ideal ventilator mode

June 1, 2016

31

The mode which deliver a breath that:

Synchronized with the patient spontaneous breathing

Maintain adequate and consistent tidal volume and minute ventilation at low airway pressure.

Response to rapid change of lung mechanic or patient demands.

Provide the lowest possible work of breathing.

A mode of ventilation is only as good as the operator who applies it.

Anatomy of Pressure waveform

Hera NICU 2016

Ti Te

Pre

ssu

re

Begin

inspiration

Cycle to expiration

Time

Flow determines rate

of rise and reaching

peak pressure

Pressure limited =

“PIP”

PEEP

∆pMAP

Which mode?

June 1, 2016

33

IMV

A/C SIPPV

SIMV

CPAPPS

SIMV&

PS

CM

VVG

BIPAP ASV

PC

V

VCV

D. Single or more type of breath

during the mode?Hera NICU 2016

Classification of ventilatory

modes

June 1, 2016

35

Trigger:

1- Machine ( IMV)

2- Patient ( SIMV, SIPPV, PS)

Control:

1- Pressure

2- Volume

3- Dual-control

Classification of ventilatory

modes

June 1, 2016

36

Cycling:

1- Time

2- Flow

3- Volume

Types of breaths during ventilation:

1- Mandatory ( controlled)

2- Spontaneous

3- Assisted

4- Supported

Intermittent Mandatory

Ventilation

Controlled Mechanical

Ventilation

Hera NICU 2016

Trigger

Controll

ed

Cycling

Types of

breaths

2 Types of breaths of IMV

June 1, 2016

38

Hazards of desynchronization

June 1, 2016

39

Baby fighting with the ventilator

Inconsistent tidal volume delivery

Inefficient gas exchange

Increase the work of breathing

Abnormally high intra-thoracic and intra-pulmonary pressures leads to Barotrauma

Decreased venous return

Increase intra-cranial pressure leads to IVH

Sub-optimal training of respiratory muscle

So, synchrony is extremely important

and can be achieved by detecting infant’s

inspiratory effort and using it to trigger

positive pressure inflation (triggered-

ventilation).

Patient trigger ventilation

sensors

June 1, 2016

41

+ −

∆ P⟇

∆ P

E

June 1, 2016

42

Neurally adjusted ventilatory

assistance

June 1, 2016

43

Steps in the process of activating

a ventilator breath(NAVA).

Trigger sensitivity

June 1, 2016

45

It determine how easy to the patient to trigger

the ventilator to deliver a breath.

Increase the sensitivity improve patient

ventilator synchronization.

High sensitivity my result in false or auto-

triggering.

The Neonatal flow sensor

Hera NICU 2016

Hot wire anemometer

Sensitive to 0.17 mL

0 - 30 lpm range

Weighs 10 grams

0.5-1 mL added

deadspace

Virtually no resistance

Inexpensive

6 month use

Flow Sensor Measurement

Principle

Hera NICU 2016

Hot wire anemometer:

• Two tiny platinum wires are heated to 400°C

• One wire is shaded to determine direction of gas flow

• Wire cooling is proportional to gas flow

• Flow is integrated with time for volume measurement

Limitations of the flow sensor

June 1, 2016

48

If ET leak, expiratory tidal volume may be

underestimated.

Imposing 1 ml of a dead space , which may

increase the WOB in very tiny preterm.

If less than the expected expiratory tidal

volume due to ET leak is registered as a

negative flow and trigger a ventilator breath,

auto-triggering.

Limitations of the flow sensor

June 1, 2016

49

Humidity; water will create significant

fluctuations of accuracy.

Secretions- surfactant; reading above or below

baseline in the presence of zero flow

Very delicate-breaks easily, wears-out due to

processing and age

Assist/Control

Synchronized Intermittent Positive Pressure

Ventilation

Hera NICU

2016

Trigger

Controll

ed

Cycling

Types of

breaths

Trigger window

June 1, 2016

51

2 Types of breaths on A/C

June 1, 2016

52

Synchronized Intermittent

Mandatory Ventilation

Hera NICU 2016

Trigger

Controll

ed

Cycling

Types of

breaths

Trigger windo

w

3 Types of breaths of SIMV

June 1, 2016

54

June 1, 2016

55

A/C Vs SIMV

June 1, 2016

56

More stable tidal volume

Less tachypnea

Smaller blood pressure fluctuation

Smaller tidal volume

Lower work of breathing

Faster weaning from mechanical ventilator

Pressure support ventilation

(PSV)

June 1, 2016

57

Trigger

Controll

ed

Cycling

Types of

breaths

Paw

V•

insp

exp

Patient or

vent ilator

initiated

inspiration PSV cycled

expiration

Peak flow

Drop to 15%

of peak flow

Pressure Support Ventilation

Set Pinsp

Hera NICU 2016

PSV Vs A/C

June 1, 2016

59

PSV, Allow the newborn more control over the

respiratory pattern, with synchronization at the

end of inspiration not only the beginning.

PSV, Decreasing asynchrony by minimize the

chance of active expiration against high

positive pressure.

PSV, Automatically adjust Ti according to

change in patient time constant breath by

breath.

PSV, Allow the infant to sigh as needed to

prevent atelectasis.

Synchronized intermittent

mandatory ventilation &

pressure support

June 1, 2016

60

Trigger

Controll

ed

Cycling

Types of

breaths

Proportional Assist Ventilation (PAV)&

Neurally adjusted ventilatory

assistance(NAVA)

June 1, 2016

61

New ventilatory modes designed to assist

spontaneous ventilation

The breath delivered is similar to PS but the

pressure support level is variable and is

proportional to patient spontaneous effort

a) The harder the patient work = the more

support by ventilator

b) The less the patient work = the less

support is provided

Tidal volume

June 1, 2016

62

Volume Guarantee

June 1, 2016

63

Working principle of Volume Guarantee. According to a set tidal volume, inspiratory pressure is automatically regulated by the ventilator.

Volume Guarantee (Dual-Control

Mode)

June 1, 2016

64

Several breaths may be needed to reach the target tidal volume after a sudden change.

Maximum

pressure

Principle of working of Volume

Guarantee

June 1, 2016

65

Test breath

Measure Vt

Inspiratory

pressure

Same

inspiratory

pressure

Inspiratory pressure

Compare to set VtMore

Equal

Less

Why volume targeted ventilation in

neonate?

Consistent VT Stable PaCO2 Stable CBF Less IVH

Hera NICU 2016

Open the lung and keep it

opened

June 1, 2016

67

The benefit of

Volume Targeted

Ventilation can not

be realized without

ensuring that the

tidal volume is

evenly distributed

throughout

an (open lung)

Ventilate in safe window

June 1, 2016

68

Volume guarantee why?

June 1, 2016

69

It is volu-trauma than baro-trauma

More stable tidal volume

Wean PIP if lung mechanics improved

Less hypo-capnea

Work better with A/C than SIMV

Bio-trauma decreased with TV 5ml/kg

Faster weaning from mechanical ventilator

Pressure Support + Volume

Guarantee

Concept of “Auto-weaning”

Hera NICU 2016

PIP

C lung

Vt

ExtubateTime

Patient control

Hera NICU 2016

Mandatory Minute Ventilation

MMV

June 1, 2016

72

Guarantee a minimum minute ventilation ( RR x TV)

If the patient maintain a MV above the set MV this mode will function like PS mode

If the patient MV falls below the set MV the mode will deliver mandatory breaths ( SIMV or IMV + VG), only the numbers of breaths that required to return patient MV to the set MV

Depends on the patient ventilatory drive

When the spontaneous breathing increased, fewer mandatory breaths will be provided

PC- MMV

June 1, 2016

73

Relationship between patient

effort and ventilator pressure

during various ventilation

modes.

Adaptive Support Ventilation

!!!???

June 1, 2016

75

Body weight

Sex

ASV delivers pressure-controlled breaths using an adaptive (optimal) scheme .

“Optimal” means minimizing the mechanical work of breathing

The machine selects a tidal volume and frequency that the patient’s brain would presumably select if the patient were not connected to a ventilator.

This pattern is assumed to encourage the patient to generate spontaneous breaths.

Different ventilatory modes

and their characteristics

Weaning byPIPInspiratory

time

Ventilator

respiration

rate

Assistance

of each

breath

Inspiratory

trigger

Ventilatory

mode

RR&

PIP

Fixe

d

Fixe

d

Fixe

dNoNoIMV

RR&

PIP

Fixe

d

Fixe

d

Fixe

dNoYesSIM

V

PIPFixe

d

Fixe

d

Variabl

eYesYesAC/

SIPP

V

PIPFixeVariablVariablYesYesPS

Thanks