introduction to pediatric ventilation

Introduction to Pediatric VentilationBill Chesser, RRT

Dept. of Cardiopulmonary CareShands Hospital

Introduction to Pediatric Ventilation

• History• Conventional Modes• Adjudicative Modes• Non-Conventional Modes• Wave Forms

Forrest Bird• 1955 Bird Mark 7

Released.• 1963 Bird Oxygen

Blender Released.• 1969 Baby Bird

Released

Bird Mark 7 (1955)• One of the first Adult

Ventilators.• Pressure Cycled.• Used today for IPPB.• Seen in “Bullitt”.

Baby Bird (1969)• Decreased Infant

Breathing Mortality from 70% to 10%.

• Time Cycled – Pressure Limited.

• Constant Flow.

Parts of a Breath• Cycle Time: The combination of the

Inspiratory and Expiratory Phase.• Cycle Time = 60 ÷ Rate• Rate of 10 has a cycle time of 6 seconds.

Parts of a Breath• Inspiratory Phase: The active part of the

breath in which the ventilator delivers the tidal volume.

• Exspiratory Phase: The passive part of the breath in which the tidal volume is released. (Conventional Ventilation).

Respiratory Terms• Compliance: The ability to stretch. (Change in

Volume/Change in Pressure)• Elastance: The ability to recoil back to a

steady state• Resistance: The impeding force to flow.

Resistance = (Ppeak – Pplateau)/Flow. Raw=(Texpiratory/3)/Compliance.

Naming the Mode• What changes Inspiration to Exhalation?• How is Tidal Volume Delivered?

Time Cycled• Inspiratory Time (TI) is set.• Tidal Volume = Inspiratory Time x Inspiratory

Flow. (minus resistance, compliance and gas compressibility)

• Inspiratory Flow may be set or variable.

Time Cycled - Pressure Limited

• Inspiratory Time is set.• Tidal Volume is variable.• VT = TInspiratory x Inspiratory Flow.• Inspiratory Flow may be set or variable.• Pressure is Set, with excess flow/pressure

being vented to the outside for the duration of the Inspiratory Time.

Volume Cycled• Inspiration ends upon the delivery of a set

Tidal Volume.• Tidal Volume is constant, Inspiratory Pressure

is variable.• Inspiratory Flow is set.• Inspiratory Time = Tidal Volume/Inspiratory

Flow x 60 (square wave only).

Volume Assured, Pressure Regulated Ventilation (VAPRV)

• Known as VC+ on PB840• Inspiratory Time is set.• Inspiratory Flow is variable.• Target Tidal Volume is set, ventilator

measures Pt compliance/resistance and calculates a PIP to reach desired VT.

Pressure Cycled• Inspiration ends and exhalation begins upon

reaching a set pressure.• Bird Mark 7 is the only Pressure Cycled

Ventilator.

Control Ventilation• The Rate sets the cycle time.• The ventilator fires at the set cycle time

regardless of patient respiratory effort.• The patient can not breathe between ventilator

breaths.• Used in Anesthesia Machines in 1950’s.

Intermittent Mandatory Ventilation

(IMV)• The rate sets the cycle time.• The ventilator fires at set cycle time regardless

of patient respiratory effort.• The patient is allowed to spontaneously breath

in between mandatory breaths with variable tidal volumes.

Synchronized Intermittent Mandatory Ventilation

(SIMV)• Rate sets the cycle Time.• Just before the Mandatory Breath, the

ventilator “Looks” for patient inspiratory effort and cycles with the patient effort.

• The patient is allowed to spontaneously breath in between mandatory breaths with variable tidal volumes.

Assist-Control Ventilation• Rate sets cycle time.• If the patient does not initiate a breath before

the cycle time, the ventilator fires.• If the patient initiates a breath before the cycle

time, the ventilator gives a Set tidal volume and Resets the cycle time.

• Tidal volume may be Volume Controlled or Time Cycled-Pressure Limited.

Airway Pressure Release Ventilation (APRV)

• Downs/Stock: Crit Care Med 1987 (May) Pg459-61

• Low Pressure Time of 0.6 – 1.2 seconds.• Set High Pressure• Set Low Pressure (5cmH2O or Lower).• Rate Usually 8 – 12 breaths/minute.

Airway Pressure Release Ventilation (APRV)

• Rate of 8 b/m is a cycle time of 7.5 seconds.• If the Low Pressure Time is 0.6 seconds, the

High Pressure Time is 6.9 seconds.

P E E P H , P E E P L a n d P S P r e s s u r e R e l a t i o n s h i p s

P E E P H a n d P E E P L a r e s p e c i f i c s e t t i n g s

P

T

P E E P H S e t t i n g

P E E P L S e t t i n g

Airway Pressure Release Ventilation (APRV)

• Used for severe ARDS.• Eliminates CO2 due to High Elastic Recoil of

Non-Compliant Lung.• Improves oxygenation and ventilation by

improving V/Q mismatch.• Allows spontaneous breathing at any point in

the ventilatory Cycle.

APRVWays of Choosing the High

Pressure• 28-35 cmH2O and work down.• Mean airway pressure of conventional

ventilation.• Plateau pressure of conventional ventilation.• PHigh and TExhalation which delivers tidal volume

of 6-10 ml/Kg.

APRV Weaning• Wean FIO2 first.• Wean PHigh to keep VT 6-10 ml/Kg.

– As compliance improves, volume will increase with same pressure.

– When PHigh is at 10-15 cmH2O, return to Conventional Ventilation or CPAP.

Pressure Support• Developed to overcome increased Work of

Breathing (WOB) caused by the ETT.• VT should be 75% of desired mechanical VT.• Having PS too high makes weaning difficult.• Tracheotomy tubes have little resistance.

Pressure Support• Tidal volume is based upon patient effort and

lung compliance.• Inspiratory phase is terminated as percent of

total flow delivered (PB840).• Flow is determined by patient inspiratory

effort.

High Frequency Ventilation (HFV)

• Rate of above 150 breaths per minute.• Good for Eliminating CO2.• High Frequency Oscillatory Ventilation.• High Frequency Jet Ventilation.

– Requires conventional ventilator for PEEP.

High Frequency Oscillatory Ventilation (HFOV)

• Amplitude• Mean Airway Pressure• Rate (Hz)• Inspiratory Time (33%)• FIO2

HFOV-Amplitude• Adjust to get good chest

“wiggle”.• Raising amplitude

decreases CO2.

HFOV-Mean Airway Pressure

• Set 2-5 cmH2O higher than conventional MAP.

• CXR to check for over distension.

• Increase MAP to raise PaO2.

HFOV-Rate• 1 Hz = 60 cycles per second.• Neonates: 10-15 Hz.• Infants: 8-12 Hz.• Pediatrics/Adults: 5-10 Hz.

HFOV-Rate• Both inspiration and

exhalation are active.• Decrease Hz to decrease

PaCO2.

HFOV-Things to Know• Takes hours to see initial results.• Suction as little as possible (Q12 hours).• Not as effective in adult population.

How Much is Too Much?• Old School – Look at the patient!

– Chest movement.– Breath sounds.– Chest X-rays.– Arterial Blood Gases.

• New School– Old School + Wave Forms

Basic Pressure Waveform

PEEP

PI P

Pplat

resistanceflow

compliancetidal vo lume

N o active breathingTreats lung as sing le unit

end -inspiratoryalveolar pres sure

W a v efo r m s

1 2 3 4 5 6

30

SecP awcm H 2O

A BC

PIP

Baseline

Mean Airway Pressure

-10

T y p ic a l F lo w C u r v e

1 2 3 4 5 6

S E C

60

60E X H

IN S P

V.

L P M

A BC

D

E

D ete c tin g A u to -P E E P

The transition from expiratory to inspiratory occurs without the expiratory flow returning to zero

1 2 3 4 5 6

SEC

1 2 0

1 2 0

V.

LPM

M andatory B reath

E xp ira tion

0 20 40 602040-60

0.2

LIT E R S

0.4

0.6

P awcmH2O

Insp ira tion

V T

Flow-Volume Loop• A: Critical Opening

Pressure.• B: Over Distension

Pressure.• C: Critical Closing

Pressure.

Volume

Pressure

A

B

C

The Whole Picture• What mode is best for the patient?• Are we over ventilating?• Should we allow permissive hypercapnia?• What is the patient fluid status?• Does the patient have infections?