Dr Satish DeopujariM.D., DNB. (Pediatrics)

National Chairperson (Ex)Intensive Care Chapter I A PFounder Chairman.....National conference on pediatric critical careProfessor of pediatrics ( Hon ) JNMC:WardhaNagpur : INDIAPHONE 0091-712-2424588 / 2420075Mobile 00 91 9823024588deopujaris@gmail.comdeopujari@rediffmail.com

The evolution of Ventilator

Three problems of ventilation

Evolution of Ventilators………………

What can we manipulate ? 1) Minute ventilation2) Pressure gradient 3) Surface are 4) Pulmonary vasculature 5) SolubilityHow can we do this ?

Applied Physics

Compliance Static compliance Dynamic compliance Resistance Work of breathing

Flow Pressure Volume Surface area

What can we manipulate ?

Compliance

Compliance is a quotient between volume and corresponding pressure change.

C = V

P

Dynamic compliance

Static compliance

The compliance of any structure is the ease is with which the structure distends ( C= ∆ V / ∆ P)

COMPLIANCE

C.C.P.

C.O.P.

VOLUME

PRESSURE

c.c.p. = critical closing pressurec.o.p. = critical opening pressure

PEEP

Pressure

Volume

Optimal Benefit Of PEEP

EX. INS.

Peak pressure

Plateau pressurePressure

Inspiratory pause

Flow

Time

Cst = Tidal volume.

Cc

Cst : static compliance Cc : circuit compliance end expiratory pressure (Pend-ex)Pend-ex = Peep + P peep

Resistance

Compliance

Static compliance

Static pressure – end expiratory pressure

Flow …………………….

Flow indicates circulation of an element per unit of time through a given place

Flow…. Linear

Turbulent

FLOW

Palv

Pmo

FLOW THROUGH A PIPE LIKE STRUCTURE REQUIRES A DRIVING PRESSURE (Palv-Pmo) TO OVERCOME THE FRICTIONAL RESISTANCE

FLOW DEPENDS ON Pressure Difference and Resistance V=P/R

Pressure …………….

Represents the force that a volume of gas exercises upon a unit area.Kinetic theory states that gas molecules bomb the walls of a container .

If volume remains constant , pressure varies in direct proportion to Temperature.If temperature remains constant , pressure varies in inverse relation to Volume .

Increase in pressure decreases volume

Resistance ……………

Resistance is defined as the relationship between pressure (p) and flow ( 0 )Therefore important when there is air flow.

R = -----------

Resistance depends upon Diameter of airway Length of airwayViscosity and density of air

Resistance during inspiration Resistance during expiration

P

O

And how can we do this ?

Conditional variables Control variables Phase variables Trigger variables Limit variables Cycle variables Base line

Conditional variables alone or in combination are

analyzed by Ventilator’s control logic.The state of this variable determines as to which of two types of breath would be delivered.

SIMV is based on timing window and accordingly the ventilator delivers …………………………….a pressure triggered ( patient ) or time triggered( machine) breath.

In this situation the patient effort and time are conditional variables for determining triggering.

Conditional variables Pressure Volume Flow Time

Control variable manipulates the conditional to cause inspiration.Pressure , volume , flow and time are control variables.

The behavior of control Variable remains constant in spite of changed Ventilatory load.

Control variable manipulates the conditionals to cause inspiration.PRESSURE , VOLUME , FLOW and time are control variables.

The behavior of control Variable remains constant in spite of changed Ventilatory load.

Pressure

Rectangular Exponential

Control variable manipulates the conditional to cause inspiration.Pressure , VOLUME , FLOW and time are control variables.

The behavior of control Variable remains constant in spite of changed Ventilatory load.

Volume

Ramp Sinusoidal

Control variable manipulates the conditional to cause inspiration.PRESSURE , VOLUME , FLOW and time are control variables.

The behavior of control Variable remains constant in spite of changed Ventilatory load.

Flow

sinusoidalrectangle ramp

ramp exponential

During pressure support ventilation though one selects a level of support the Inspiration continues till predetermined flow rate or termination criteria is reached.During PSV patient determines the Rate ……………..Inspiratory time…Flow……………..

Peak pressure

Plateau pressureResistance

Compliance

End of inspiration

Volume

Flow

Pressure

Volume control

End of insp. flow

Volume

Flow

Pressure

Pressure control

What does not change …….1) Volume curve 2) Exp. Flow curve

End of insp. flow

Volume

Flow

Pressure

Pressure control

Peak p.Plateau p. Resist.

Compliance

End of insp. flow

Volume

Flow

Pressure

Volume control

Volume limited and pressure limited ventilation ………….

Volume limited pressure limited

Advantages

Tidal Volume guaranteed Precise control of Inspiratory flow Easy detection of changed respiratory impedance

Precise control pf pressure Decelerating flow reported to improve distribution of ventilation decrease dead space ventilation decrease PIP match Inspiratory flow

Disadvantages

PIP vary Inspiratory flow may not match the patients needs

Variable tidal volume Changes in impedance not easily detected

Modes of ventilation or moods of ventilation

PRESSURe

FLOw

VOLUMe

A B C

A normal lung B decreased compliance C increased resistance

Controlled Ventilation…………….

SIMV

Patient triggered ventilationSynchronized to patient breathif the threshold is met .

Patient controlled variables Respiratory rateInspiratory time Clinician controlled variables PIP if pressure limited Tidal volume if volume cycled Inspiratory time if time cycledFlow SIMV rate

Flow cycling …….Insp. Terminated at % of peak flow rather than time………… Synchronizes expiratory and Insp. flow thus total synchrony achieved.

When SIMV  is used, the patient receives three different types of breath:The controlled (Mandatory) breath.Assisted (synchronized) breaths.Spontaneous breaths, which can be pressure supported.

A B C

A .Controlled and time triggeredB .Spontaneous C .Synchronized and assisted

Flow

PaW

Volume

Trigger

Spontaneous breath

Assisted breath

Back up ventilation period

Controlled breath

Spontaneous volume

Trigger Spontaneous breath

Pressure

Volume

Pressure support

Pressure support ventilation is a spontaneous mode of ventilation.Inspiratory effort is assisted by the ventilator at an airway pressure that remains constant during the phase of inspiration.Inspiration is terminated when the peak Inspiratory flow reaches a preset level. (usually 25%)

Patient determines……………… Rate Inspiratory time Airflow

PRVCA control mode, which

delivers a set tidal volume with each breath at the lowest possible peak pressure. Delivers the breath with a decelerating flow pattern that is thought to be less injurious to the lung……

Volume SupportEquivalent to pressure supportset a “goal” tidal volumethe machine watches the delivered volumes and adjusts the pressure support to meet desired “goal” within limits set by you.

Airway Pressure Release Ventilation

Can be thought of as giving a patient two different levels of CPAP Set “high” and “low” pressures with release time.Length of time at “high” pressure generally greater than length of time at “low” pressure.By “releasing” to lower pressure, lung volume is allowed to decrease to FRC

Certain other issues

Fixed insp. TimeTermination sens. off Termination sens. on

Flow

Pressure

Inspiratory cycle off…………

Proper Inspiratory cycle terminationavoids lung hyperinflation and

Increased work of breathing

40 %

10 %

10 %

5%

1%

Exp.

Insp

.

PEEP PIP

Vt.

COMPLIANCE LINE

Pressure limited…

Over distension

Exp.

Insp

.

PEEP PIP

Vt.

COMPLIANCE LINE

Pressure limited…

Exp.

Insp

.

PEEP PIP

Vt.COMPLIANCE LINE

Volume limited…

Pressure – Volume loops

Low compliance

A

B C

D

Volume

Pressure in CM

B C

Volume

Pressure in CMA

D

Normal resistance

Increased resistance

volume

Pressure

Elastic work

Resistive work

Triggering ……………………

Triggering ……………………Neuro – Ventilatory coupling ………….

Central Nervous System

Phrenic Nerve

Diaphragmatic contraction

Chest Wall and Lung expansion

Air way pressure , flow and volume

NAVA Ventilator

Current Technology

Ideal technology

Neurally Adjusted Ventilatory Assist

EA di Waveform

Tidal volume ÷ P plat – PEEP Tidal volume ÷ PIP – PEEP PIP – P plat ÷ Flow rate PIP- P2 ÷ Flow rate

Static compliance Dynamic characteristics

Maximum resistance index

Minimum resistance index

Elastic and resistive property of respiratory System

Time constant

×

Resistive property

Conditional variables

Control variables

Pressure : Volume : Flow

Phase Variables

Trigger : Limit : cycle : Base line

You can comfortably SLEEP even in difficult situation if you know your physiology well……………

Thanks

SLEEP

Mechanical Ventilation is a blend science and art ………………….