This document discusses the role of mechanical ventilation in congenital heart disease. It begins by defining mechanical ventilation and its history. It then covers the goals, ideal design, and components of mechanical ventilation. Several sections discuss how mechanical ventilators work, including different modes, parameters, and the effect on the cardiovascular system. The document concludes by covering indications for mechanical ventilation in congenital heart disease and initial ventilator settings.

1. Role of Mechanical Ventilation in Congenital
Heart Disease
Dr. Md. Mostafizur Rahman Bhuiyan
Phase A Resident
Department of Paediatric Cardiology

2. Definition:
• Mechanical ventilation • Normal ventilation
It is a device to inflate the lungs artificially by
positive pressure

3. History:
• The earliest breathing machine was
the Drinker respirator. It was
invented in 1928 and was known as
an ‘iron lung’ for people whose
breathing muscles had
been paralyzed by polio. They used
negative pressure to help patients
breathe while lying inside the iron
lung’s airtight chamber.
•In 1949, American engineer John
Haven Emerson developed an
positive pressure anesthetic
ventilator.

4. Goals of Mechanical Ventilation:
1. Achieve and maintain adequate
pulmonary gas exchange
2. Minimize the risk of lung injury
3. Reduce patient work of breathing
4. Optimize patient comfort
5. To normalize blood gases and provide
comfortable breathing

5. Ideal Ventilator Design
1. Achieves all the important goals of mechanical
ventilation
2. Provides a variety of modes that can ventilate
even the most challenging pulmonary diseases
3. Has monitoring capabilities to adequately assess
ventilator and patient performance
4. Has safety features and alarms that offer lung
protective strategies

6. Components of MV

7. How mechanical Ventilator works:
A) Breath:
A breath is one cycle of positive flow (inspiration) and negative flow
(expiration)
Inspiratory time is defined as the period from the start of positive flow to the
start of negative flow.
Expiratory time is defined as the period from the start of expiratory flow to
the start of inspiratory flow.
Mechanical
Time (sec)
Spontaneous
Paw(cmH2O)
Inspiration
Expiration
Expiration
Inspiration

8. How mechanical Ventilator works:
A) Breath: A breath is assisted if the ventilator does work on the patient.
an assisted breath is identified as a breath for which airway pressure
(displayed on the ventilator) rises above baseline during inspiration.
An unassisted breath is one for which the ventilator simply provides the
inspiratory flow demanded by the patient and pressure stays constant
throughout the breath.
Assisted Controlled

9. How mechanical Ventilator works:
B) Control: A ventilator assists breathing using either –
1) Volume control (VC) means that 
1) both volume and flow are preset prior to inspiration.
2) The ventilator will continue to "force" that set volume into the lungs
regardless of the pressures being generated, i.e Vt is guaranteed.
2) Pressure control (PC) means that  the pressure of each breath remains
constant. In other words, when the ventilator reaches a preset pressure
limit inspiration is terminated. The amount of volume delivered is entirely
dependent on the lung compliance of the patient. The main benefit of
pressure controlled ventilation is -
a. airway pressures are controlled.
b. mechanically ventilated much more comfortable and better tolerated.
c. It also decreases the risk of barotrauma to the alveoli and bronchi.
3) Time control (TC) means that  none of the main variables (pressure,
volume, or flow) are preset. In this case only the inspiratory and expiratory
times are preset.

10. How mechanical Ventilator works:
Trigger: The start of inspiration is called the trigger
1. Time triggering: The machine is set to give a
breath every 8 seconds, or 10 seconds, or
whatever rate you program into the machine.
2. Pressure triggering: When a pt initiates a
breath, the ventilator circuit detects a drop in
intrathoracic pressure & delivers a breath to
the patient.
3. Flow triggering: during pt induced inspiration,
ventilators detect changes in flow & delivers a
breath to the pt.

11. How mechanical Ventilator works:
• Cycle: The end of inspiration is called the cycle event.
The cycling of a mechanical ventilator breath occurs after a set value is reached.
Four variables are used to determine when to cycle to exhalation:
1. Pressure Cycling
1. When a certain pressure threshold is reached, inspiration is cycled into
exhalation.
2. Pressure cycling can be viewed as a safety feature to avoid elevated and
sustained inspiratory pressure.
2. Time Cycling
1. MV breath switches from inspiration to expiration after a set time threshold is
reached. This can be accomplished by setting the respiratory rate, inspiratory
time, or inspiratory-expiratory ratio.
3. Volume Cycling
1. The ventilator cycles to expiration once a set tidal volume has been delivered.
4. Flow Cycling
1. For a given tidal volume when the patients inspiratory flow is decreased to a
predetermined level (25% of peak inspiratory flow) the breath would cycle
into exhalation.

12. ACCELERATING
DECELERATING
SINE
SQUARE
How mechanical Ventilator works:
Different air flow patterns:

13. Modes of Ventilation:
the manner or method a breath is delivered by the ventilator
1. Continuous Mandatory Ventilation (CMV)
Previously known as controlled mechanical
ventilation
2. Assist/Control Ventilation (A/C)
3. Synchronized Intermittent Mandatory Ventilation
(SIMV)
4. Spontaneous Modes
1. Pressure Support Ventilation (PSV)
2. Continuous Positive Airway Pressure (CPAP)

14. CMV
•When the termination of a breath is
under the control of the mechanical
ventilator, it is referred to as a
mandatory breath.
•Indication:
•seizure,
•chest injury
• if pt “fights” the vent
•complete rest for pt. for 24 hr.,
•In this mode pt. is properly
medicated with a combination of
sedatives, respiratory depressants
and neuromuscular blockers.
Mechanical
Time
(sec)
Paw(cmH2O)
Time
Triggered
Breath

15. Volume control
Tadal volume ml
RR b/m
PEEP cmH2O
PIP depends on pt
Fio2 %
Ti / I: E 0.1 – 5 Sec with
I:E 1:2
Trigger Flow > 0
Pressure - 20 to 0
Pause time 0 – 30% or
0-1.5 sec
Inspiratory
Rise time
Adult : 0 to 0.4
Infant: 0 to 0.2
OTHER NAME: IPPV /CMV, VCV-
A/C, Volume A/C,
VC-CMV, VC-AC
Pressure control
Tidal volume ml
RR b/m
PEEP cmH2O
PIP cmH2O above
PEEP
Fio2 %
Ti / I: E 0.1 – 5 Sec with
I:E 1:2
Trigger Flow > 0
Pressure - 20 to 0
Inspiratory
Rise time
Adult : 0 to 0.4
Infant: 0 to 0.2
OTHER
NAME:
P-CMV, PCV-A/C,
Pressure A/C

16. Assist/Control Ventilation (A/C)
•Assist-control refers to a mode of ventilation when a patient receives a
combination of ventilator-initiated and patient-initiated mandatory breaths.
•If a patient on an AC of 14 with a total breathing rate of 16 breaths per minute, is
triggering two additional breaths per minute, but, all 16 breaths are being delivered
by the ventilator.
•Advantages of AC mode:
•Increased patient comfort
•Easy corrections for respiratory acidosis/alkalosis.
•Low work breathing for the patient.
•Disadvantages of AC mode:
•barotrauma is a concern in stiff lungs.
•If exhalation time is inadequate auto-PEEP develops.  diminished venous
return  hypotension.
•hyperventilation

17. SIMV
 Breaths are given at a set minimal rate, however if the patient chooses to
breath over the set rate no additional support is given
 Like AC, SIMV can deliver set tidal volumes (volume control) or a set pressure
and time (pressure control)
“synchronized window” refers to the time just prior to time triggering in which the vent. is
responsive to the pt.’s effort (0.5 sec is typical)
Advantages include maintaining resp. muscle strength, reduces V/Q mismatch, decreases
mean airway press., helps wean pt
 SIMV is usually associated with greater work of breathing than AC ventilation and
therefore is less frequently used as the initial ventilator mode

18. SPONTANEOUS
•A spontaneous breath is a breath for which the patient
both triggers and cycles the breath.
•A spontaneous breath may be
•assisted or
•unassisted.
•Rate and tidal volume during spontaneous breathing
are determined by patient. Role of ventilator during
spontaneous vent. is to provide the
•flow adequate to fulfill a patient’s insp. demand
•provide adjunctive modes such as PEEP or PS to
complement the spontaneous effort
Time (sec)Inspiration
Expiration

19. CPAP:
•PEEP is applied on expiration.
•PEEP causing alveoli to remain open and not fully
deflate.
•This mechanism for maintaining inflated alveoli helps
increase partial pressure of oxygen in arterial blood,
and an increase in PEEP increases the PaO2
SPONTANEOUS

20. Pressure support:
The patient initiates every breath and the ventilator delivers breath
with the preset pressure value.
In Pressure Support
•Patient regulates their own respiratory rate and their tidal
volume.
•the set inspiratory pressure support level is kept constant
•a decelerating flow.
•Pressure support improves oxygenation, ventilation and
decreases work of breathing.
•Cycling: when the inspiratory flow rate decreases, inspiration
ends and expiration starts
PSV is entirely dependent on the patient’s effort; if the patient
becomes apneic, the ventilator will not provide any mechanical
breath.
SPONTANEOUS

21. Parameters of MV:
Tidal volume (Vt) : (Tidal Volume - the amount of air delivered with
each breath.)
8-10 ml/kg
Respiratory Rate - number of breaths per minute
Ti / I : E 0.1 – 5 Sec with
I:E 1:2
Pressures
PIP (maximum amount of pressured delivered during each
breath ) - 16-20cmH2O
PEEP 3-5 cmH2O
Pressure support 5-10
FiO2 – fraction of inspired oxygen
Trigger:
Flow > 0
Pressure - 2 to 0
Mode
Flow pattern

22. Effect of MV on cardiovascular system
• The cardiovascular and respiratory systems act as a
functional unit.
• Mechanical ventilation – modifies pulmonary volumes,
• Tidal volume by influencing autonomic nervous system
reactivity can provoke tachy- or brady-cardia
• Decreases cardiac filling volumes (pre-load)
• alters pulmonary vascular resistances.
• intrathoracic pressures are enlarged, which cause
• decrease in right atrium filling and
• an increase in right ventricle afterload.

23. Effect of MV in cardiovascular system: contd.
• If coronary flow is impaired, myocardial contractility is
reduced.
• In cardiac failure – MV is especially beneficial because :
– it corrects hypoxia and respiratory acidosis,
– decreases the work of breathing, and
– improves stroke volume.
• Mechanical ventilation in congenital heart diseases is indicated
either –
– as lifesaving support or
– as physiopathological treatment to modify the ratio
between pulmonary and systemic flow

24. Indication of MV
1. Respiratory failure:
• Hypoxia (PaO2 < 50)
• Hypercapnia (PaCO2 > 50)
• Respiratory distress (RR increased), use of accessory muscles
2. Shock
3. Chest trauma
4. Neuromuscular dysfunction
5. stroke & General anaesthesia
6. Electrolyte imbalance
7. Acute severe airflow obstruction
8. Acute lung injury/ARDS
9. Inability to protect airway
10. Congenital heart disease

25. Indication of MV
Cardiac indication:
1. CHF
• Sepsis Syndrome
• cardiomyopathy,
• infectious myocarditis
2. Tachyarrhythmias
3. Cardiogenic Shock : In the immediate postoperative
period in complex congenital heart disease –
1. patients should be on controlled mechanical
ventilation until hemodynamic functions improve.
2. Adequate PEEP should be applied to prevent and
relieve atelectasis.

26. Indication of MV: congenital heart disease
CHD causing CHF or cardiogenic shock thus requiring MV are:
•Defects with increased pulmonary blood flow (if excessive pulmonary blood
flow is present, the aim of respiratory support is to increase pulmonary
vascular resistance by using high levels of airway pressure and even by
delivering FiO2<21%. )
1. Very large ASD, VSD, PDA  volume overload
2. Truncus arteriosus: CHF in older children due to post repair truncal
insuffciency or conduit stenosis.
3. TAPVC – comes with heart failure
•Left Heart Outflow Tract Obstruction
1. Aortic stenosis (AS) : severe aortic insuffciency and ultimately left
heart failure is seen in
1. Critical AS in the neonatal period &
2. older children following repair of AS suffer from restenosis
2. Coarctation of the aorta (CoA) : may present as late as 8 weeks of
age with signs of cardiogenic shock.
3. Hypoplastic left-sided heart syndrome (HLHS): commonly presents
within the fIrst 7 days of life.

27. Indication of MV: congenital heart disease
•Defects with decreased pulmonary blood flow (there is low
pulmonary flow, the lowest possible intrathoracic pressures
should be used, especially in cases of pulmonary hypertension,
which will also require high FiO2.) Immediate intervention is
indicated in any cyanotic infant whose ABG shows :
•pH <7.28 or
•PaCO2 >50 mmHg
•PaO2 <50 mmHg on a
•FiO2 >0.5
1. Tetralogy of fallot (TOF) : for management of recurrent severe
tet spells
2. Critical pulmonary stenosis (PS) and pulmonary atresia with
intact ventricular septum
3. Transposition of great arteries (TGA) associated VSD may
present with CHF

28. Indication of MV: congenital heart disease
•Arrhythmias.
•Dilated and hypertrophic cardiomyopathies are a common
etiology of pediatric heart failure.
•hypotension  due to low cardiac output and in the most
severe cases, fulminant pulmonary edema
•ET intubation indicated to:
1. Decrease work of breathing (to decrease the
metabolic demands of both the respiratory muscles
and heart, thus decreasing stress on the already
failing cardiopulmonary system)
2. PIP: higher mean airway pressure will decrease
intrapulmonary shunting created by the fluid filled
alveolus.
3. PEEP: higher, it may limit venous return to the heart

31. ET intubation:
• ET tube size:
– Gestational age /10, if cuffed 0.5 size less
• Depth of insertion:
– internal tube diameter (in mm)×3.
– in children >2 years of age: Depth of insertion (cm)=(age in
years/2)+12; [eg. 10yr/2+12=17cm
• Confirm placement:
– Capnography
– Lung sound
– Vapour in ET tube
– No gastric distension
– Stat improving
• cuffed ET Tube  cuff pressure should be below 20 cm H2O.
• Uncuffed TTs should be sized to allow a leak ∼20 cm H2O

32. Initial ventilator setting:
Initial
ventilator
setting
Premature
neonate
Neonate Infant
/small child
< 12 kg
Large child
> 12 kg or,
Adolescent
Mode Pressure
control
Pressure
control
Volume
control+PS
Volume
control
Rate 40-50 20-25 Infant/Small
Child 16-20
12-16
PEEP 3-5 3-5 3-5 3-5
Ti 0.3 – 0.4 0.5 – 0.6 0.6-0.7 0.7-0.9
PIP 16-20 16-20 16-20 18-25
Vt 5-8 ml / kg 5-8 ml / kg 5-8 ml / kg 5-8 ml / kg
Fio2 0.6 and titrate or 100% and wean down

33. Complication of mechanical ventilation
1. Increased airway pressures and lung volumes
1. Barotrauma/volutrauma(stretch injury):-
pneumothorax, pneumopericardium,
pneumoperitoneum, subcutaneous emphysema.
2. Decreased cardiac filling and poor perfusion.
3. Other organ dysfunction-renal, hepatic, and CNS.
Pulmonary parenchymal damage.
4. Adverse effects on gas exchange.
5. Increased extravascular lung water.
2. Endotracheal/tracheostomy tube
1. Tracheal mucosal swelling,
2. ulceration or damage.
3. sinusitis/middle ear infection.
4. Laryngeal edema, subglottic stenosis.
5. Granuloma formation leading to airway obstruction.

34. 3. Nosocomial infections
1. Ventilator associated pneumonias.
2. Sepsis.
4. Pulmonary circulation
1. Increased pulmonary vascular resistance.
2. Compression of alveolar vessels.
5. Mechanical operational problems
1. Mechanical ventilator/compressor failure/alarm failure.
2. Inadequate humidification.
6. Other systems
1. Decreased hepatic blood flow.
2. Decreased cerebral venous drainage.
Complication of mechanical ventilation

35. Weaning
1. Is the cause of respiratory failure gone or
getting better ? –
2. Is the patient well oxygenated and ventilated ?
3. Can the heart tolerate the increased work of
breathing?

36. Extubation : indication
•“Awake ” patient
•control of airway reflexes,
•minimal secretions
•Minimal oxygen requirement
•Minimal rate -SIMV rate of < 10,
•Minimize pressure support (5- 10)
•Adequate muscle tone
•Minimal/no inotropic support,
•normal electrolytes and no fluid overload

37. Extubation - Procedure
1. Keep NPO 4hrs before planned extubation
2. Suction endotracheal tube and deflate cuff if using a cuffed tube.
3. Suction the oral cavity and nostrils.
4. Following instrument should be ready –
1. laryngoscope and correct size ETTube.
2. Nebulisation with beta stimulant/adrenaline
3. Intravenous steroids dexamethasone 0.6mg/kg iv(maximum dose of 12mg)
4. Ideally, ventilator to be on standby at least 24hrs post extubation.
5. Intravenous frusemide
6. Do blood gas 20mins after extubation;
7. Post extubation CXR not needed routinely but only if clinically indicated by desaturation
or increased work of breathing.
• Anticipate extubation failure in all patients and parents should be made aware earlier on so
that there is no disappointment.

38. Thank you