MECHANICAL VENTILATION IN PEDIATRICS

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MECHANICAL VENTILATION IN PEDIATRICS

• PRESENTED BY DR.MAYSA ABDULHAQ
• Moderator DR.NADWA AL-ZOHLOF

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Contents

• Basics of ventilators/ control pattern and modes.
• Indications /aims .
• Initial settings/adjusting of ventilator
  settings
• Problems during ventilation and complications
• Weaning stratigies

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The Basics of Mechanical Ventilation
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• Depending on connecting prosthesis, mechanical
  ventilation is defined
• non-invasive ventilation when inferior airways
  are not invaded to introduce external gases into
  lungs. Prostheses largely used are nasal and
  facial masks to perform non-invasive.
• invasive ventilation when tracheal intubation or
  tracheostomy are used to connect patient to
  ventilator.

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There are two ways to give a breath
Volume Controlled
Pressure Controlled
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Ventilators Modes control variables

• Control Variables
• The control variables\independent variables,
  determined by the clinicians and include
  pressure, flow, or volume.
• must overcome the elastic and resistive forces to
  allow gas delivery to the patient.
• During expiration, the elastic and resistive
  elements of the respiratory system are passive,
  and expiratory waveforms are not directly
  affected by the modes of ventilation or the
  controller.

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volume controller

• When the clinician presets a volume pattern, it
  operates as a volume controller Volume is an
  independent variable and pressure is a dependent
  variable. pressure then varies with compliance.
  Expiration is passive, and the expiratory profile
  is not directly affected by the mode of
  ventilation but rather by compliance and
  resistance

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Volume Control

• The patient is given a specific volume of air
  during inspiration.
• The PIP observed is a product of the lung
  compliance, airway resistance and flow rate. The
  ventilator does not react to the PIP unless the
  alarm limits are violated.
• The PIP tends to be higher than during pressure
  control ventilation to deliver the same volume of
  air.

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What do you set?
Volume Controlled
You set Tidal volume Peak flow Rate FiO2 PEEP
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Volum Control Ventilation

• Controlling pH and pCO2 is done by controlling
  minute ventilation. You can set both the
  respiratory rate and the tidal volume.
• Controlling pO2 you can adjust the FiO2, the PEEP
  and, indirectly, the PIP by adjusting the tidal
  volume (bigger TV yields bigger Pmax) although we
  dont do this so much in practice

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Pressure Controller

• when the clinician presets the pressure pattern,
  the ventilator operates as a pressure controller
  Pressure is the independent variable, and volume
  is the dependent variable determined by the level
  of pressure.and is the function of lung
  compliance and airways resistance.

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Pressure Control

• The pressure is constant throughout inspiration.
• The ventilator adjusts the flow to maintain the
  pressure.
• Flow decreases throughout the inspiratory cycle.
• Volume delivered depends upon the inspiratory
  pressure, I-time, pulmonary compliance and airway
  resistance.
• The delivered volume can vary from
  breath-to-breath depending upon the above
  factors. MV not assured.
• Good mode to use if patient has large air leak,
  because the ventilator will increase the flow to
  compensate it.

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What do you set in PC?
Pressure Controlled
You set Pressure limit Time spent in inspiration
(Itime) Rate
You set FiO2 PEEP
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Pressure Control Ventilation

• Controlling the pH and pCO2 is done by
  controlling the minute ventilation. You can set
  the RR, but the TV is managed indirectly.
• Controlling the pO2, again you can adjust the
  FiO2 and the PEEP, in addition you control the
  PIP.

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Volume vs. Pressure
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Modes of Ventilation

• the mode of ventilation is a description of the
  way a mechanical breath is delivered.
• In general we are trying to accomplish one of two
  things for a patient using mechanical
  ventilation either to control their ventilation
  and oxygenation, which they are unable to do, or
  to support them as they wean from ventilatory
  support. Hence, we can look at ventilator modes
  as either Control Modes, or Support Modes.

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Modes of Ventilation

• Mechanical ventilation can be applied both
  invasively or non-invasively in the following
  ways
• Controlled mechanical ventilation Pressure
  controlled Ventilation PC, Volume Controlled
  Ventilation VC, , Pressure Regulated Volume    
  Controlled Ventilation PRVC , High Frequency
  Ventilation ,CMV and IMV.(which are rarely , if
  ever, used today),
• Supported spontaneous breathing Pressure Support
  Ventilation and     Volume Support Ventilation
• Mixed respiratory support (SIMV)Synchronized
  Intermittent Mandatory Ventilation .SIMV/PS
• Assisted spontaneous breathing Continuous
  Positive Airway Pressure (CPAP

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AC (assist control) or VC (Volume Control)

• Characteristics preset rate and tidal volume
  (sometimes PIP), full mechanical breath is
  delivered either triggered by patients
  respiratory efforts, or if not sufficient- the
  preset mechanical rate is maintained
  automatically.
• Uses for patients who have a very weak
  respiratory effort, allows synchrony with the
  patient but maximal support. Not a weaning mode,
  as at any rate they are getting complete
  mechanical support.
• Advantages a fairly comfortable mode, providing
  a lot of support.
• Disadvantages can lead to hyperventilation if
  not closely monitored, not able to wean in this
  mode.

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Assist Control (A/C)
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PRVC (Pressure Regulated Volume Control)

• Characteristics a volume control assist control
  mode, In this mode, a target minute ventilation
  is set.
• The ventilator will adjust the flow to deliver
  the volume without exceeding a target inspiratory
  pressure.
• Uses in patients with high airway pressures,
  although it can be used in any patient.
• Contraindications none in particular
• Advantages No change in minute ventilation if
  pulmonary conditions change. The desired TV can
  be guaranteed at the lowest PIP necessary to
  achieve it thus minimizing the barotrauma.
  Disadvantages new, Hard to use on a
  spontaneously breathing patient or one with a
  large air leak. Not a weaning mode.

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IMV (Intermittent Mandatory Ventilation)

• Characteristics set breath delivered at a fixed
  interval. No patient interaction, but allow the
  patient to breath through the ventilator circuit
  by providing gas flow( unlike CMV). pressure or
  volume control,
• Contraindications none really, unfriendly to
  older patients
• Advantages regular guaranteed breath
• Disadvantages does not allow patient to breath
  with the ventilator except by chance..Does not
  work with the patient

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Intermittent Mandatory Ventilation (IMV)
Ventilator lets patient breathe spontaneously BUT
does not change its plan of ventilation.
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PS /Pressure Support

• Characteristics supports each spontaneous breath
  with supplemental flow to achieve a preset
  pressure.
• All the breaths are triggered by the patient
• Prest value PIP, PEEP, FiO2.
• the patint determine rate, Ti, IE ratio, TVi.
• Needs intact resp. drive.
• Uses In the spontaneously breathing patient this
  helps overcome the airway resistance of the
  endotracheal tube. Can be very helpful for
  weaning.
• Contraindications patient who is not
  spontaneously breathing, i.e. on muscle relaxants
  
• Advantages helps overcome resistance of tube,
  making spontaneous breathing easier

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VS/Volume Support

• Characteristics variable level of pressure
  support is delivered on each spontaneous
  patient-triggered breath in order to achieve
  preset tidal volume.
• All breaths are triggered by the patient.
• The clinician pre set iTV, FiO2, PEEP,
• The patient determine the RR, Ti, IE ratio.
• Uses a weaning mode. The concept is that as the
  patient becomes stronger, or more awake they will
  make more respiratory effort on their own. The
  more effort they make the less support they will
  need from the ventilator and hence the level of
  pressure delivered will get smaller.
• Contraindications patient who is not
  spontaneously breathing, as there is no back-up
  rate.
• Advantages greatly decreases the number of
  interventions needed to wean patient from a
  ventilator versus traditional weaning

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Weaning by Support Ventilation
Ventilators work of breathing
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Weaning by Support Ventilation
Ventilators work of breathing
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Weaning by Support Ventilation
Ventilators work of breathing
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The following modes fall into both Control and
Support categories in that they have set rates,
but the spontaneous breaths are not controlled,
so they can be used in weaning.
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SIMV (Synchronous IMV)

• Characteristics Derived from Intermittent
  mandatory ventilation (IMV)
• Preset mechanical breath delivered within an
  interval based on the preset respiratory rate.
  Ventilator spends part of the interval waiting
  for spontaneous breath from the patient, which it
  will use as a trigger to deliver a full breath.
  If not sensed it will automatically give a breath
  at the end of the period. Any other breaths
  during the cycle are not supplemented.
• Patient does ALL work of breathing on the
  spontaneous breaths.
• Plus some work on the SIMV breaths. (Tries to
  synchronize to patients efforts)
• TV on the spontaneous breaths depends entirely
  upon patient effort and lung mechanics
• Can be pressure or volume controlled
• Uses commonly used in many settings. Can be a
  weaning mode (see also with PS)
• Contraindications none in particular
• Advantages allows work with the patient,
  somewhat more friendly.
• Disadvantages Any other breaths during the cycle
  are not supplemented/ not good for fighting
  patients.

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SIMV
SIMV divides Tb into Mandatory periods (Tm) and
Spontaneous periods (Ts)
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SIMV
If patient tries to breathe during Tm, the
ventilator gives a FULLY ASSISTED BREATH
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SIMV
If patient tries to breathe during Ts, the
ventilator allows the patient to take the
breath. Assistance may or may not be provided
with PRESSURE SUPPORT (coming soon)
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Triggering the Ventilator
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SIMV/PS

• Characteristics combination of the previous two
  modes. Extra breaths in the cycle are
  supplemented with pressure support.
• Uses useful in most circumstances, including
  weaning.
• Contraindications none in particular.
• Advantages allows both synchrony with the
  patient and help in overcoming the resistance in
  the endotracheal tube, to allow easier
  spontaneous breathing
• Disadvantages none in particular. PS does not
  add anything in the patient who is not
  spontaneously breathing.

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Assisted Spontaneous Breathing

• Continuous Positive Airway Pressure CPAP is a
  mode of ventilation, the pressure above the
  atmospheric pressure maintained throught out the
  resp. cycle during spontaneous breathing, thus
  pressure in the airway is always positive

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CPAP

• This method presents several advantages because
  of
• increased lung volume and FRC and improve in
  ventilation/perfusion ratio.
• preventing and resolving atelectasis.
• reduced work of breathing and prevention of
  muscle fatigue .
• Applied by invasive and noninvasive methods

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CPAP is not advisable in

• high risk patients. severe respiratory effort to
  maintain ventilation
• any patient without spontaneous respiratory
  effort.
• Not a good idea in a patient with obstructive
  pulmonary disease (like asthma).
• hypercapnia

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CPAP is indicated in

• for patients with upper airway soft tissue
  obstruction
• or tendency for airway collapse.
• As a final mode prior to extubation in some
  patients.

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CPAP

• This is very similar to PEEP, except that the
  inspiratory pressure is also maintained at the
  CPAP level, leading to support on inspiration and
  resistance on exhalation.

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So what is PEEP?
PEEP is the residual pressure above atmospheric
pressure maintained at end of expiration.
PEEP can be added to any mode of mechanical
ventilation A/C PC or VC SIMV PC or VC
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PEEP

• Good.
• Recruits Alveoli
• ? FRC
• Redistributes Pulmonary Edema Fluid
• ?intrapulmonary shunt
• ? PaO2

• Bad.
• ?d Venous Return / C.O.
• May ? ICP,/ intensify cerebral ischemia
• Overdestention/?s Risk of Barotrauma
• May impair oxygenation????

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• Figure 6 - Tracheo-bronchial distention due to
  PEEP application leads to a progressive
  recruitment of alveoli. On the left, 2 PEEP on
  the right, 10 cm H2O PEEP.

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What is Auto-Peep?
INSP
FLOW
EXP
Expiratory flow ends before next breath
Next breath begins before exhalation ends
Obstructive lung disease (pursed lip) Rapid
breathing (breath stacking) Forced exhalation
(anxiety)
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Conditions associated with auto-PEEP

• Patients with obstructive lung disease( sever
  Asthma)
• Kinked or obstructed ETT with secretions.
• In adequate Te in mechanically ventilated
  patients

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Signs of air trapping (auto-PEEP)

• Over expansion of the chest
• Decreased chest wall expansion.
• CO2 retention.
• Cardiovascular dysfunction.

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Ventilator settings in auto-PEEP

• Low or Zero PEEP
• Long Te( as possiple)
• Low RR
• Relieve underlying causes( bronchospasm,
  secretions, position of ETT)

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Who needs a ventilator?

• If you don't know where you are going, you might
  wind up someplace else.
• Try to figure out why the patient is requiring
  intubation.

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Who needs a ventilator?

• Cant oxygenate (low PaO2/SPO2)
• Cant ventilate (high PaCO2)
• Cant participate or protect airway (low GCS)
• If youre not sure whether or not the patient
  needs a ventilator, the patient needs a
  ventilator.

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Assessment of the need for mechanical ventilation

• Symptoms
• DyspneaOrthopneaIncreased cough or
  wheezeSomnolence
• Signs
• StridorTachypneaUse of accessory muscles
  of respirationRetractionsProlonged expiratory
  phaseParadoxical abdominal motion on
  inspirationCyanosis
• Laboratory tests
• Arterial blood gas measurementPulse
  oximetric studiesChest radiographMeasurements
  of pulmonary mechanics

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Aims of mechanical ventilation

• Always remember assisted ventilation is a
  supporitive technique its NOT a curative

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Aims of mechanical ventilation

• Provide ventilation( CO2 removal)
• Optimal systemic oxygenation
• Decrease the work of breathing

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Ventilator Settings

• There is no optimum mode of ventilation for any
  disease state optimum method of weaning
  patients from mechanical ventilation.
• Mechanical ventilation is associated with a
  number of diverse consequences include
  volutrauma, barotrauma, oxygen toxicity.
• To Minimize side effects, the physiologic
  targets need not to be in normal range.

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Initial Ventilator Settings

• Rate 20-24 for infants and preschoolers
  16-20 for grade school kids 12-16 for
  adolescents
• TV 10 -15ml/kg
• PEEP 3-5cm H2O
• FiO2 100
• I-time 0.7 sec for higher rates, 1sec for lower
  rates
• PIP (for pressure control) about 24cm H2O.

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Adjusting The Ventilator

• Obtaining a blood gas early after intubation
  (15-20 minutes after being on the ventilator)
  will help you decide if you are moving in the
  right direction.
• Its better to accept a certain degree of resp.
  acidosis and possibly even hypoxemia to avoid
  ventilator induced lung injury. (pemisive
  haypercapnia and relative hypoxia)
• It may be better to risk O2 toxicity than to use
  high pressure.

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Adjusting The Ventilator

• pCO2 too high
• pCO2 too low
• pO2 too high
• pO2 too low
• PIP too high

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pCO2 Too High

• Patients minute ventilation is too low.
• Increase rate or TV or both.
• If using PC ventilation, increase PIP.
• If PIP too high, increase the rate instead.
• If air-trapping is occurring, decrease the rate
  and the I-time and increase the TV to allow
  complete exhalation.
• Sometimes, you have to live with the high pCO2,
  so use bicarbonate to increase the pH to gt7.20.

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pCO2 Too Low

• Minute ventilation is too high.
• Lower either the rate or TV.
• Dont need to lower the TV if the PIP is lt20.
• TV needs to be 8ml/kg or higher to prevent
  progressive atelectasis
• If patient is spontaneously breathing, consider
  lowering the pressure support if spontaneous TV
  gt7ml/kg.

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pO2 Too High

• Decrease the FiO2.
• When FiO2 is less than 40, decrease the PEEP to
  3-5 cm H2O.
• Wean the PEEP no faster than about 1 every 8-12
  hours. Sudden decease in PEEP may lead to
  precipitous decrease in oxygenation and FRC.
• While patient is on ventilator, dont wean FiO2
  to lt25 to give the patient a margin of safety in
  case the ventilator quits.

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pO2 Too Low

• Increase either the FiO2 or the mean airway
  pressure (MAP).
• Try to avoid FiO2 gt70.
• Increasing the PEEP is the most efficient way of
  increasing the MAP in the PICU.
• Can also increase the I-time to increase the MAP
  (PC).
• Can increase the PIP in Pressure Control to
  increase the MAP,
• May need to increase the PEEP to over 10, but try
  to stay lt15 if possible.

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PIP Too High

• Decrease the PIP (PC) or the TV (VC).
• Increase the I-time (VC).
• Change to another mode of ventilation.
  Generally, pressure control achieves the same TV
  at a lower PIP than volume control.
• If the high PIP is due to high airway resistance,
  generally the lung is protected from barotrauma
  unless air-trapping occurs.

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Permissive Haypercapnia and Relative Hypoxia)

• Attempts to maintain normal values during
  treatement of acute lung injury expose airways
  to ventilator-induced lung injury
• Barotrauma
• Volutrauma
• Oxygen toxicity

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Permissive Haypercapnia and Relative Hypoxia)

• So permissive haypercapnia and relative hypoxia
  are treatment strategies to prevent the
  development of ventilator-induced injury.
• Used in the acute or recovery phase of acute
  lung injury or ARDS
• Allows for respiratory acidosis with metabolic
  compensation
• Progressinve increase in PaCO2 to 60-100 and may
  be higher.
• Rate of development of hypercapnia is 5-10mmHg/hr
  will allow renal compensation. But rapid increase
  in PCO must be avoided.

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Permissive Haypercapnia and Relative Hypoxia)

• To avoid oxygen toxicity
• Keep FiO2 lt 50
• Maintain low PaO2 near 50 mm Hg
• with fairly adequate O2sat gt 85
• The tow strategies may be used separately to or
  together depending on the clinical conditions.

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Contraindications for permissive hypercapnia and
hypoxia

• Suspected intracranial hypertention
• Cerebrovasculer disease
• Cardiac arrhythmias
• Sever pulmonary hypertension
• Sever systemic hypertension
• Sever cardiac failure
• Sickle cell disease

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Indication for permissive hypercapnia and hypoxia

• Acute lung injury or ARDS.
• Weaning from mechanical ventilator.
• Patients with air leak syndrom
• Status asthmaticus in resp. failure.
• Post operative recovery.

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Inverse ratio ventilation

• The clinician must increase the Ti to greater
  than Te for IE ratio more than.11
• Benefit in refractory hypoximic ARDS that not
  responding to other strategies.
• Can be used in both volume and pressure control
  ventilation, but volume control is not preferred

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Effects of inverse ratio

• This maneuver will recruits the alveoli by
• 1-Prolonged time constant will increase the
  mean airway pressure.
• 2- increasing the Te will increase the Paw
  by causing auto-PEEP.
• Alveolar recruitment will improve V/Q and enable
  the clinician to decrease PIP, PEEP, and FiO2

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During inverse ratio

• Provide adequate sedation and neuromuscular
  blockade
• Small tidal volum 5-8 ml/kg
• PIP lt 35 mmHg
• PEEPlt 10 cm H2O
• Side effects
• decrease cardiac out put/ may need pulmonary
  art. catheter for close haemodynamic monitring .
• Increase risk of barotrauma and volutrauma

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Complications of Mechanical Ventilation

• Pulmonary
• Barotrauma
• Ventilator-induced lung injury
• Nosocomial pneumonia
• Tracheal stenosis
• Tracheomalacia
• Pneumothorax
• Cardiac
• Myocardial ischemia
• Reduced cardiac output

• Gastrointestinal
• Ileus
• Hemorrhage
• Pneumoperiteneum
• Renal
• Fluid retention
• Nutritional
• Malnutrition

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Acute Deterioration

• DIFFERENTIAL DIAGNOSES
• Pneumothorax
• Pneumonia
• Malposition of the ETT
• Pulmonary edema
• Airway occlusion
• Ventilator malfunction
• Mucus plugging
• Air leak

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Physical Exam

• Tracheal shift
• Pneumothorax
• Wheezing
• Bronchospasm
• Mucus plugging
• Pulmonary edema
• Pulmonary thromboembolism

• Asymmetric breath sounds
• Pneumothorax
• Mainstem intubation
• Mucus plugging with atelectasis
• Decreased breath sounds bilaterally
• Tube occlusion
• Ventilator malfunction

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Weaning from Mechanical Ventilation

• Weaning from mechanical ventilatory support has
  traditionally been a mix of science and art
• It requires waiting until the disease process
  that caused the patient to need assisted
  ventilation reverses and then successfully
  decreasing ventilator support to a level that
  allows for extubation.

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Weaning Priorities

• Wean PIP to lt35cm H2O
• Wean FiO2 to lt60
• Wean I-time to lt50
• Wean PEEP to lt8cm H2O
• Wean FiO2 to lt40
• Wean PEEP, PIP, I-time, and rate towards
  extubation settings.
• Can consider changing to volume control
  ventilation when PIP lt35cm H2O.

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Extubation Criteria

• Neurologic
• Cardiovascular
• Pulmonary

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Neurologic

• Level of sedation should be low enough that the
  patient doesnt become apneic once the ETT is
  removed.
• No apnea on the ventilator.
• Patient must be able to protect his airway, e.g,
  have cough, gag, and swallow reflexes.
• Must be strong enough to generate a spontaneous
  TV of 5-7ml/kg
• Being able to follow commands is preferred.

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Cardiovascular

• Patient must be able to increase cardiac output
  to meet demands of work of breathing.
• Patient should have evidence of adequate cardiac
  output without being on significant inotropic
  support.
• Patient must be hemodynamically stable. includes
  good perfusion ,age-appropriate blood pressure.

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Pulmonary

• Patient should have a patent airway.
• Pulmonary compliance and resistance should be
  near normal.
• Patient should have normal blood gas and
  work-of-breathing on the following settings
• CPAP/PS for 1hr for older children and
  adolescents
• FiO2 lt40
• PEEP 3-5cm H2O
• Spontaneous TV of 5-7ml/kg

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THANK YOU