Mechanical Ventilation of the Critically Ill Child

73
Mechanical Ventilation of the Critically Ill Child: Where do we stand in 2006? Ronald C. Sanders Jr., M.D., M.S. Assistant Professor, Dept. of Pediatrics Division of Critical Care, Shands Children’s Hospital University of Florida Gainesville, Florida

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Mechanical Ventilation of the Critically Ill Child

Transcript of Mechanical Ventilation of the Critically Ill Child

Page 1: Mechanical Ventilation of the Critically Ill Child

Mechanical Ventilation of the Critically Ill Child:

Where do we stand in 2006?

Ronald C. Sanders Jr., M.D., M.S.Assistant Professor, Dept. of Pediatrics

Division of Critical Care, Shands Children’s Hospital

University of FloridaGainesville, Florida

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Outline

Physiological Concepts• Pediatric Considerations• Work of Breathing (WOB)

Indications for Ventilatory Assistance• Initial Settings for Mechanical Ventilation

Mechanical Ventilation and the Pediatric Heart Patient

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Basic Respiratory Physiology

West, JB. Respiratory Physiology. 5th Edition. 1995.

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Junqueira LC et al.Basic Histology. Fifth Edition.1986.p.390.

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Junqueira LC et al. Basic Histology.Fifth Edition.1986.p.395.

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Basic Respiratory Physiology

Alveolar Gas Equation

PAO2 = PIO2

-PA

CO2

RPI

O2 = (PB - PH2O) x FIO

2 ; R = 0.8

West, JB. Respiratory Physiology. 5th Edition. 1995

A-a gradient = PAO2- PaO2

( Acceptable gradient < 20 mm Hg onroom air or less than 70 on 100% O2)

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Basic Respiratory PhysiologyLi

ters

6

Total Lung Capacity

Vital Capacity

Tidal Volume

Residual Volume

Functional Residual Capacity

Inspiratory Reserve Volume

Expiratory Reserve Volume

8

4

2

0

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Distribution of Blood FlowWest Zones

Zone 1

Zone 2

Zone 3

PA

Pa

P

> Pa > Pv

> PA > Pv

a> Pv > PA

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PEEP

Definition• Positive end expiratory pressure

Gattinoni L, Caironi P, Pelosi P and Goodman L. What Has CT Taught Us about ARDS? Am J Respir Crit Care Med 2001

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Pressure-Volume Relationships

100

75

50

25

0-40 -20 0 20 40

Pressure (cm H20)

Vita

l Cap

acity

(%)

Chest wall

Lung

Chest wall and lung

TLC

FRC

At high lung volumes, complianceof the resp systemis decreased p-vcurve flattens as it becomes fullydistended

At low lung volumesreduced compliancemay be due to stiffeningof chest wall.

Whenever lung volumesfalls below closing volume,lung compliance will alsofall due to derecruitmentof functioning units

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Children vs. Adults

Airway• In children, the airway is more anterior and the

epiglottis is floppy.

• The airways are smaller.– Poiseulle’s Law states that resistance is inversely

related to the 4th power of the radius (laminar flow).

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Children vs. Adults

Chest Wall• In children, the chest wall is more compliant

which limits the capacity for gas exchange.

• This anatomical feature may necessitate increased respiratory rates to maintain adequate minute ventilation. This leads to increased metabolic activity.

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Children vs. Adults

0

10

20

30

40

50

60

70

Premature Term > 2 Years

DiaphragmIntercostal Muscle

Type

I M

uscl

e Fi

bers

(%)

(slo

w-tw

itch,

hig

hly

oxid

ativ

e)

Cote CJ, Ryan JF, Todres ID et al. A practice of anesthesia for infants and children. 2nd ed. Philadelphia: WB Saunders, 1993.

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Outline

Physiological Concepts• Pediatric Considerations • Work of Breathing (WOB)

Indications for Ventilatory Assistance• Initial Settings for Mechanical Ventilation

Mechanical Ventilation and the Pediatric Heart Patient

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Respiratory System Loads

The combined effect of compliance and resistance constitute the load experienced by the ventilator and ventilatory muscles.

The elastic load is the “pressure” necessary to expand the lungs and chest wall (i.e. volume/compliance).

The resistance load determines the “pressure” necessary to deliver gas at a particular flow rate (i.e. flow x resistance)

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FLOWFLOW

VOLUMEVOLUME

RESISTANCERESISTANCE

COMPLIANCECOMPLIANCE

VolumeVolume

ComplianceCompliancePressure =Pressure = + flow x resistance+ flow x resistance

P = Flow x ResistanceP = Flow x Resistance

Compliance = Compliance = ∆∆ VolumeVolume∆∆ Pressure Pressure

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Total Work of Breathing

Total Work Total Work of Breathingof Breathing ==

PhysiologicPhysiologicWorkWork

ImposedImposedWorkWork++

Elastic work toElastic work toexpand lungs andexpand lungs andchest wall and flowchest wall and flowresistive work to resistive work to overcome airwayovercome airwayresistanceresistance

Resistive workResistive workimposed by imposed by breathing breathing apparatus (e.g.apparatus (e.g.endotracheal tube,endotracheal tube,breathing circuit, breathing circuit, and ventilatorand ventilator’’ssdemanddemand--flow system)flow system)

WOBT

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V

P

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P

V

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Patient and Ventilator Work

VT

PAW

Pes

Insp

TIME

Exp

WOB P

WOB P + V

WOB V

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Evaluating WOB in Ventilated Subjects

• Are there differences in WOB based on mode of ventilation?

Hypothesis: The WOBT will be unchanged between the SV300,VIP and the EV4 despite mode of triggering.

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MethodsFor WOB data, airway pressure and flow rate were measured at the proximal end of the ET tube using a differential flow transducer.Intrapleural pressure was measured using an esophageal catheter.The transducers and esophageal catheter were connected to a Bicore CP-100 pulmonary monitor.

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MethodsVentilator

BicoreCP-100

0

0

0

VolumeFlowratePES

HME

PNEUMOTACHOGRAPH(MeasurementofVolumeandFlowrate)

EsophagealPressure(P )ES

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WOB-Campbell Diagram

II

EE

--4040 --3030 --2020 --1010 00 1010

5050

3535

VVTT

FRCFRC

CCLLCCCWCW

100100

Flow resistive workFlow resistive work

Elastic workElastic work

Imposed workImposed work

Stored energy of theStored energy of thechest wallchest wall

Work imposed byWork imposed bythe breathing app.the breathing app.

PhysiologicPhysiologicWorkWork

% V

ital Capacity

% V

ital Capacity

IntrapleuralIntrapleural pressure (cm Hpressure (cm H220)0)

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Total Work of BreathingSV 300 vs VIP Bird

(Both on Pressure Triggering)Pressure Support 5 cm H2O

0

0.2

0.4

0.6

0.8

1

1.2

1.4

SV 300Bird

* p=0.028**p=0.028

*87%**122%

PEEP 0 PEEP 3cm H2O

WOBTJ/L

Sanders RC, Thurman TL, Holt,SJ, Taft K and Heulitt MJ. Work of BreathingAssociated with Pressure Support Ventilation in Two Different Ventilators.

Pediatric Pulmonology. 32:62-70, 2001

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Total Work of BreathingSV 300 (Flow Trigger) vs VIP Bird (Pressure Trigger)

Pressure Support 5 cm H2O

0

0.2

0.4

0.6

0.8

1

1.2

1.4

SV 300Bird

* p=0.043**p=0.028

*125%

**144%

PEEP 0 PEEP 3

WOBTJ/L

Sanders RC, Thurman TL, Holt,SJ, Taft K and Heulitt MJ. Work of BreathingAssociated with Pressure Support Ventilation in Two Different Ventilators.

Pediatric Pulmonology. 32:62-70, 2001

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POWER BUSY

Digital Analog

12345678

10

910111213141516

BIOPAC Systems, Inc. MP100

Analog C

hannelsZERO SPAN CD 15

ZERO SPAN CD 15

SV300

pneumotach

Transducer

Carrier demodulators

UIM100A

HMETo PigTo Ventilator

All signals collected from the Drager Babylog 8000were routed via the pneumotach.

Transducer

Millennia XKU 300MHZ

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a- b Start of deflection of flow to most negative deflection of pressurea - c Start of deflection of flow to maximum flow

SV 300

17.500 18.000 18.500 19.000seconds

0.00000

5.00000

10.0000

15.0000

cmH

20

pres

sure Insp. Flow

Flow

Volume

Insp. PressureExp. Pressure

Pressure

Exp. Flow

Start of deflection of flow

Maximum flow

Most negative deflection of pressure

a b c

Vent signal

Flow, and Pressure are signals received from pneumotach, Flow is integrated for VolumeInsp. Flow, Exp. Flow, Insp. Pressure and Exp. Pressure are signals received from the SV 300 VentilatorVent Signal is a signal received from the ventilator to indicate patient trigger

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Patient and Ventilator Work

VT

PAW

Pes

Insp

TIME

Exp

WOB P

WOB P + V

WOB V

a b c

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SV 300, Flow Trigger, Pressure Support 5, PEEP 0

17.500 18.000 18.500 19.000seconds

0.00000

5.00000

10.0000

15.0000

cmH

20

pres

sure

a- b Start of deflection of flow to most negative deflection of pressurea - c Start of deflection of flow to maximum flow

a b c

Insp. Flow

Flow

Volume

Exp. Pressure

PressureExp. Flow

Vent signal

Insp. Pressure

84 ms 235 ms

-.38 cmH20

delta p = .53 cmH20

Sanders RC, Thurman TL, Holt,SJ, Taft K and Heulitt MJ. Work of BreathingAssociated with Pressure Support Ventilation in Two Different Ventilators.

Pediatric Pulmonology. 32:62-70, 2001

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Evita 4 Flow Trigger, Pressure Support 5, PEEP 0

a- b Start of deflection of flow to most negative deflection of pressurea - c Start of deflection of flow to maximum flow

1.5000 2.0000 2.5000 3.0000seconds

-5.00000

0.00000

5.00000

10.0000

cmH

20

pres

sure

Flow

Volume

Pressure

341 ms

a b c139 ms

-2.48 cmH20

delta p = 3.94 cmH20

Flow, and Pressure are signals received from pneumotach, Flow is integrated for Volume

Sanders RC, Thurman TL, Holt,SJ, Taft K and Heulitt MJ. Work of BreathingAssociated with Pressure Support Ventilation in Two Different Ventilators.

Pediatric Pulmonology. 32:62-70, 2001

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Bird (Pressure Trigger)

-5.00000

0.00000

5.00000

10.0000

cm H

20

pres

sure

Flow

Start of deflection of pressure

Volume

Maximum flow

Most negative deflection of pressure

a b c d e

Maximum pressure

Flow

Start of deflection of pressure

~ 440 ms

a- b Start of deflection of pressure to most negative deflection of pressurea - c Start of deflection of pressure to maximum flowa - d Start of deflection of pressure to second increase in pressurea - e Start of deflection of pressure to max pressure

.0000 1.5000 2.0000 2.5000seconds

Flow, and Pressure are signals received from pneumotach, Flow is integrated for Volume

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Outline

Physiological Concepts • Pediatric Considerations • Work of Breathing (WOB)

Indications for Ventilatory Assistance• Initial Settings for Mechanical Ventilation

Mechanical Ventilation and the Pediatric Heart Patient

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Indications for Mechanical Ventilation

Ventilatory FailureHypoxiaHemodynamic InstabilityICP ManagementAirway protection

Slutsky AS. Consensus Conference on Mechanical Ventilation. Intensive Care Medicine 1994

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Ventilatory Failure

A clinical diagnosis!ApneaPaCO2 > 60 (in patient with previous normal lungs)Vital capacity < 15 ml/kgDead space/tidal volume ratio> 0.6

Martin LD, Bratton SL. Principles and Practice of Respiratory Support and Mechanical Ventilation. In: Rogers MC,ed. Textbook of Pediatric Intensive Care, 1996.

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Hypoxia

Cyanosis despite FiO2 > 0.6PaO2 < 70 torr with FiO2 > 0.6

AaDO2 > 300 torr with FiO2 = 1.0Qs/QT > 15-20% Qs/QT = Cco2 – Cao2

Cco2 – Cvo2

Martin LD, Bratton SL. Principles and Practice of Respiratory Support and Mechanical Ventilation. In: Rogers MC,ed. Textbook of Pediatric Intensive Care, 1996.

[Normal = 0.03 – 0.07]

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Hemodynamic Instability

Imbalance between metabolic supply and demand.

Typically, objective measures of oxygen and ventilation (e.g. PaCO2) are normal.

Agitation, pain, blood draws and performing procedures places the patient in peril.

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Hemodynamic Instability

2 y.o male with 3 day history of shortness of breath, lethargy and emesis.

Patient intubated due to respiratory distress.

Determined to have poor pulses & echocardiogram reveals an ejection fraction of ~ 20%.

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Dilated Cardiomyopathy Case

0

50

100

150

200

250

300

6.9

7

7.1

7.2

7.3

7.4

7.5

7.6

PaCO2PaO2pH

Extubated

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3-18-06

3-13-06 3-16-06

3-21-06

Dilated Cardiomyopathy Case

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Dilated Cardiomyopathy Case

0

5

10

15

20

25

30

Base Deficit

Lactate

Fluid Balance+ 450 ml

Lasix, BumexMetalozone

IVF

BNP Level>54,000

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Outline

Physiological Concepts • Pediatric Considerations • Work of Breathing (WOB)

Indications for Ventilatory Assistance• Initial Settings for Mechanical Ventilation

Mechanical Ventilation and the Pediatric Heart Patient

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Recommended Criteria For Acute Lung Injury (ALI)

Acute onset of respiratory disease with bilateral infiltrates on a frontal chest x-ray.

Pulmonary Artery Wedge Pressure (PAWP) < 18 mm Hg or no clinical evidence of left atrial hypertension[yet may coexist]

Bernard GR et al. The American-European Consensus Conference on ARDS Am J Respir Crit Care Med 1994.

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Recommended Criteria For ALI & ARDS

*OxygenationALI PaO2/FiO2 < 300ARDS PaO2/FiO2 < 200

* regardless of PEEP

Bernard GR et al. The American-European Consensus Conference on ARDS Am J Respir Crit Care Med 1994.

Comparison of P/F Ratios

0

50

100

150

200

250

300

350

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43

Time (Days)

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Acute Lung Injury [ALI] Case #1

BC was a 5 y.o. with history of renal transplant for ESRD 2º to HUS who presented to an outside hospital for evaluation of fever.

She developed respiratory failure due to CMV pneumonitis that progressed to endotracheal intubation and conventional mechanical ventilation 8 days later.

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ALI Case #1Her pulmonary status deteriorated further and she required high frequency oscillatory ventilation (HFOV).

She developed renal failure and pancreatitis.

Her ventilation support was maximized and pulmonary hemorrhage developed.

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ALI Case #1After 5 days in the PICU, Tertiary Care Center (TCC) was consulted for Extracorporeal Membrane Oxygenation (ECMO). Patient did not meet criteria.

She was transferred to TCC after a 17 day stay in PICU. Her peak inspiratory pressures were between 40 and 50 cm H2O.

The patient required multiple fluid boluses and she developed refractory hypoxemia and hypercarbia despite maximum support. Care withdrawn after 46 days.

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ALI Case #2

JM was a 16 y.o. WM who was involved in a MVA at an intersection in Northwest AR vs. an 18-wheel semi-truck.

He sustained multiple injuries including a clavicle fx, rib fx, pneumothorax, ruptured spleen, T2 spine fx and multiple lung contusions.

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ALI Case #2 He required splenectomy and was placed on mechanical ventilation.

During his hospitalization, he developed multiple pneumothoraces and pneumomediastinum requiring several chest tubes. A tracheobronchial tear was suspected, but never confirmed.

He accidently extubated himself on the 2nd day and had a questionable aspiration event.

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ALI Case #2 Transferred to TCC 5 days after accident for ventilation management of Acute Respiratory Distress Syndrome (ARDS).

In referring hospital: FIO2 100%, Positive End-Expiratory Pressure (PEEP) 15 cm H2O and Tidal Volume (TV) of 700ml (12.5 ml/kg). Weight = 56 kg

At TCC: FIO2 100%, PEEP 17 cm H2O and TV decreased to 350 ml (6.5 ml/kg)

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ALI Case #2

Over the next 45 days, the patient eventually required 18 days of HFOV, developed neuropathy of critical illness, frequent management of pulmonary secretions and eventually tracheostomy.

He was successfully weaned to a tracheostomy collar and transferred to the rehabilitation unit.

His recovery went well, the tracheostomy was reversed and he was discharged home 4 months after the accident.

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A-a Gradient Comparison

0

100

200

300

400

500

600

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43

Time (Days)

JM Mean A-a Grad

BC Mean A-a Grad

Alv

eola

r-ar

teria

l oxy

gen

grad

ient

(A

-a g

radi

ent)

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Comparison of P/F Ratios

0

50

100

150

200

250

300

350

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43

Time (Days)

PaO 2

/ Fi

O 2

Rat

ios

BM PF Ratios JM PF Ratios

Comparison of P/F Ratios

PaO

2/F

iO2

Rat

ios

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Initial Mechanical Ventilation Settings

ObjectivesSupport oxygenation and ventilation while avoiding ventilator-induced injury.

Goals• Peak Inspiratory Pressure (PIP) < 35 cm H2O• Tidal Volume (TV): 6-8 ml/kg• FIO2

< 0.55

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Initial Mechanical Ventilation Settings

FIO2at 1.0 (in noncardiac patients)

• Pulse ox > 95% and PaO2> 80 mm Hg

Positive End-Expiratory Pressure (PEEP)• Start at 5 cm H2O and titrate in 2 cm H2O steps

every 5 minutes.

Inspiratory Time (“I Time”)• Newborn 0.6 second• One year to 12 years 0.7 second• Adolescent-Adult 1.0 second

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Initial Mechanical Ventilation Settings

Rate: normal for age• < 1 year 30 - 35• 1-6 years 25 - 30• > 6 years 20 – 25(Rates need to be lower in pts with obstructive lung

disease)

Tidal Volume: 6-8 ml/kg in patients with lung injury• TV of 10 ml/kg is reasonable in patients without

lung injury.• Always assess for symmetrical chest sounds and

movement.

I:E ratio: 1:2

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Cardiopulmonary Bypass and Respiratory Mechanics

20-30minutes

4hours

7hours

Induction ofanesthesia

OffBypass

Ranieri, VM et al. Time-course of impairment of respiratory mechanics after cardiac surgery and cardiopulmonary bypass. Crit Care Med 1999;

27:1454-1460 .

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HLHS Case

5 day old girl with HLHS characterized by poor cardiac function and cyanosis.

Patient taken to the OR for Norwood Stage I correction with modified Sano technique.

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HLHS & The Sano Procedure

HypoplasticLeft Heart

Small Aorta Sano Shunt

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HLHS Case

Pre-operativeCXR

Post-operativeCXR

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HLHS Case

POD #1CXR

POD #3CXR

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Cardiopulmonary BypassCongenital Heart Disease

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Mechanical Ventilation in the Post-Operative Congenital Heart

What is an appropriate amount of PEEP?

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Congenital Heart Disease Pulmonary Vascular Resistance

60

70

80

90

100

110

120

60 100 150 175Lung Volume (ml)

Vasc

ular

Res

ista

nce

(cm

H2O

/L/m

in)

PVR is lowest at FRC!

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Summary

Compared to adults, infants and children have developmental features that result in lower respiratory reserves.

After deciding on mechanical ventilation, think of elastic and resistive loads faced by the patient after re-establishing homeostasis.

Always provide PEEP to maintain FRC in order to keep alveoli recruited, PVR decreased and volutrauma/barotrauma minimized.

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Go Gators!!