PAEDIATRIC VENTILATION

1
PAEDIATRIC VENTILATION
Contributors Chris Smith, Hilary Klonin, Alan
Minty, Ann-Marie Olphert, Nicky Hart, John
Meliones, Ira Chiefetz, Donna Hamel, Mike
Gentile, Steve Middleton-Draeger, Draeger
Teaching Materials with permission, David
Thomas, Doug Dixon
2
BASIC PHYSIOLOGY
3
Cardiorespiratory SystemGoals

• Provide appropriate oxygen delivery (DO2) to meet
  metabolic demands of the tissues
• If DO2 inadequate to meet the oxygen needs,
  anaerobic metabolism develops, which results in
  acidosis and organ dysfunction
• Elimination of carbon dioxide generated

4
Oxygen Supply

• Cardiac Output x Oxygen Content of blood
  CO
  (CaO2)
• Cardiac output heart rate x stroke volume
  CO HR SV
• Oxygen content of (1.34 x Hb x O2 Sat)
  blood (CaO2) (0.003 x PaO2)
• What we measure PaO2
• The amount of oxygen actually dissolved in the
  blood, the PaO2 is very small under most
  circumstances and does not usually form a
  significant part of oxygen delivery

5
Oxygenation

• Dependant on
• V/Q matching
• Inspired oxygen concentration

6
Hypoxia

• Hypoxic gas mix
• Shunt
• V/Q mismatch

7
CO2 Level

• Dependant on
• CO2 production
• Adequate fresh gas flow
• Dead space ventilation
• Minute ventilation

8
Dead Space Ventilation

• Dependant on
• Cardiac Output
• Lung disease and ventilation of under perfused
  alveoli
• Fresh gas flow

9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
BASIC PRINCIPLES OF VENTILATION
13
Mechanical VentilationGoals

• Oxygenation / Ventilation
• Minimise toxicity - Barotrauma /
  volutrauma - Oxygen toxicity - Negative
  impact on CV system
• Optimise patient work of breathing
• Maximise patient comfort

14
Types of VentilationVolume limited ventilation

• Ventilator delivers set tidal volume

15
Types of Ventilation Pressure Limited Ventilation

• Ventilator delivers set pressure

16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
Volume Limited Ventilation

• Flow pattern often constant flow
• Advantages - Maintains minute ventilation
• Disadvantages - Potential for PIP if
  pulmonary compliance decreases
• Indications - Routine ventilation -
  Stable minute ventilation essential

21
Pressure Limited Ventilation

• Flow pattern constant or variable
• Advantages - Pressure limit may decrease
  barotrauma - Variable flow limits PIP, increases
  MAP
• Disadvantages - Tidal volume affected by
  compliance Indications - Routine
  ventilation (constant flow) - Acute lung injury
  (variable flow)

22
Variable, Decelerating Flow

• Advantages - Matches flow to spontaneous
  demand - Responds to changes in lung mechanics
• Disadvantages - Not available for all breath
  types
• Indications - Pulmonary compliance -
  Lung units with variable time constants -
  Spontaneously breathing patients - Variable work
  demands (asleep/awake)

23
PEEP

• Positive end expiratory pressure
• Holds airways open at the end of expiration

24
Trigger Ventilation

• Patient can initiate breaths
• Decreases patient breathing against the
  ventilator
• Decreases barotrauma and intrinsic PEEP
• Decreased risk of pneumothorax

25
Increased Work of Breathing
Tube resistance
High airway resistance -obstructive diseases
Pressure Support
Stiff lung tissue -low compliance
26
Pressure Support

• Patients breath is supported by pressure from the
  ventilator
• Patient can control time of inspiration and
  expiration

27
Pressure Support

• Each additional sensed patient effort is
  supported with a pressure limited
  breath. - WOB (ETT effects) -
  Tidal volume of spontaneous breaths - Trigger
  pressure or flow - Limit pressure -
  Cycle flow or time - Flow decelerating,
  variable

28
Pressure Support

• Advantages - Improved patient - ventilator
  synchrony - WOB since each pt effort is
  supported
• Disadvantages - Inadequate triggering may
  limit use - Rapid RR may lead to intrinsic
  PEEP - ETT leaks may prolong inspiratory phase
• Indications - Active spontaneous breathing
• - Weaning

29
Mixed Ventilation Patterns
Mechanical strokes
Spontaneous efforts
These two forces should never act against each
other
30
SETTING AND ASSESSING GOALS
31
Set Aims... of ventilation

• OXYGENATION Most oxygen is carried on
  Haemoglobin, therefore use saturation
• CARBON DIOXIDE Use paCO2 and pH

32
Cardiorespiratory EconomicsO2 Supply

• Oxygen Delivery (oxygen supply) Cardiac
  Output x Oxygen Content DO2 C.O. x CaO2
• CaO2 (1.34 x Hb x O2 Sat) (0.003 x PaO2)

33
CO2 Level

• Dependant on
• CO2 production
• Minute ventilation
• Dead space ventilation
• Fresh gas flow

34
Mechanical Ventilation Goals

• Oxygenation / Ventilation
• Minimise toxicity - Barotrauma /
  volutrauma - Oxygen toxicity - Negative
  impact on CV system
• Optimise patient work of breathing
• Maximise patient comfort

35
Oxygenation index

• FiO2 x MAP/Pa O2 mmHg
• Normal 1-2
• Consider high frequency 15-25
• Consider ECMO 40
• High mortality if 40, or failure to respond to
  alternative therapy over 6 hours

36
P/F ratio

• PaO2mmHg/FiO2 (21 0.21)
• Useful for non ventilated patients
• Normal 500
• Ventilate 300
• Alternative strategies 150

37
Compliance

• Change in lung volume per unit change in pressure
• Measure of lung stiffness
• Decreased if lungs are collapsed or over
  distended
• Used to assess PEEP
• Normal is 1cm H2O/ kg
• Extubation above 0.8cm/H2O/kg

38
Resistance

• Pressure required to produce air flow
• Detects problems in the larger airways
• Trends can be used to assess
• bronchodilator therapy

39
(No Transcript)
40
(No Transcript)
41
(No Transcript)
42
Intrinsic PEEP

• PEEP not applied by the ventilator
• The lungs do not decompress to baseline at the
  end of expiration
• Can occur in ventilated or spontaneously
  breathing patients
• Breathing rate dependant

43
(No Transcript)
44
Intrinsic PEEP Adverse Effects

• WOB
• mean intrathoracic pressure
• cardiac output
• trigger sensitivity
• VT in pressure limited breaths
• PIP in volume limited breaths
• Treatment strategies exp. time, adjust PEEP

45
Intrinsic PEEP Treatment

• No treatment e.g. ARDS
• Decrease respiratory rate
• Decrease inspiratory time
• Termination sensitivity
• Adjust PEEP

46
(No Transcript)
47
Optimising Tidal Volume
48
Decreased Compliance
7 yrs ARDS
49
Optimising PEEP
50
Oxygen Toxicity

• Aim to use inspired oxygen less than 60

51
Haemodynamics

• Mean airway pressure will affect venous return
• Decreased venous return will decrease cardiac
  output
• Some compensation is possible by increasing the
  CVP with fluid therapy

52
Mechanical Ventilation Goals

• Oxygenation / Ventilation
• Minimise toxicity - Barotrauma /
  volutrauma - Oxygen toxicity - Negative
  impact on CV system
• Optimise patient work of breathing
• Maximise patient comfort

53
SPECIFIC VENTILATION STRATEGIES
54
BIPAPPressure Ventilation

• Bi level positive airway pressure
• Patient can breathe spontaneously at upper and
  lower airway pressures
• Advantages of pressure limited ventilation but
  allows spontaneous breathing

55
(No Transcript)
56
Autoflow

• Allows spontaneous breathing
• Uses lowest pressure to deliver guaranteed tidal
  volumes
• Can be sculpted to deliver a decelerating flow
  with a constant plateau pressure

57
Airway Pressure Release Ventilation

• Ventilation at 2 different pressure levels
• Most time spent in high pressure level
• CO2 removal by short periods at lower pressure
  level
• Upper pressure level lower than conventional BIPAP

58
Mandatory Minute Volume Ventilation

• Use where tight CO2 control required
• Spontaneous breathing with automatic adjustment
  of mandatory ventilation to the patients CO2
  requirement
• Use with pressure limitation
• Use with autoflow

59
Apnoea Ventilation

• Automatic switch over to volume controlled
  ventilation if breathing stops

60
Permissive Hypercapnia

• Allow paCO2 to rise
• Maintain pH above 7.28
• Buffers have been used

61
Permissive Hypercapnia Contraindications

• High ICP
• Cardiac arrhythmias
• Possibly pulmonary hypertension

62
Permissive Hypoxia

• Allow lower than normal saturation
• Follow patient tolerance carefully
• Look for acidosis, lactate rise etc.
• Monitor haemoglobin to optimise oxygen carriage

63
ARDS

• Adult respiratory distress syndrome
• Non-homogenous lung disease
• Some lung units collapsed
• Some lung units over distended
• Marked V/Q mismatch

64
(No Transcript)
65
(No Transcript)
66
Acute lung injury ARDS

• Vascular injury
• Intrapulmonary shunt
• Hypoxemia
• PA hypertension
• Parenchymal injury
• Pulmonary compliance
• FRC
• Airway pressures to maintain VT
• Risk of barotrauma and O2 toxicity

67
(No Transcript)
68
Alveolar Recruitment

• Using ventilation manoeuvres and strategies to
  open collapsed alveoli
• Includes sustained inflation, high PEEPs, inverse
  ratio ventilation

69
(No Transcript)
70
(No Transcript)
71
Prone positioning

• A trial of prone positioning may be indicated in
  patients with ALI ARDS
• Earlier use of proning (i.e., before fibrosis
  starts) may be more beneficial
• Have adequate personnel available
• Have an organized plan for rotation

72
Prone positioning

• When proning, support the weight of the pressure
  points
• Use variables of oxygenation (PaO2 SpO2) and O2
  delivery (SvO2 lactate) to assess benefits of
  prone position
• Leave prone as long as there is an apparent
  benefit without unacceptable risk
• Assess skin integrity, airway, lines regularly

73
Risks of proning

• Loss of airway and lines
• Periorbital and conjunctival edema
• Ocular pressure
• Facial skin breakdown
• Peripheral arm nerve injury
• Difficult to resuscitate in the case of an arrest

74
ARDS Aims of Therapy - Summary

• Open closed lung units
• Do not over distend normal lung units
• Set realistic ventilation aims
• The open lung approach
• Use alveolar recruitment high PEEP, high mean
  airway pressure, sustained inflation
• Prone position
• Do not use large distending tidal volumes

75
Bronchiolitis

• Inflammation of the smaller airways
• Collapse of smaller airways
• Air trapping, intrinsic PEEP
• Secretions throughout the bronchial tree
• Upper airway secretions
• Apnoea
• Septic/Encephalitic syndromes

76
(No Transcript)
77
Bronchiolitis Ventilation strategy

• Use adjuncts to avoid ventilation if possible
• Best strategy unclear
• Suggested permissive aims, adequate peep,
  pressure support

78
Tight CO2 Control Ventilation

• Use pre-set tidal volume and rate
• Mandatory Minute Ventilation
• Use auto flow to minimise pressure peaks

79
Mechanical Ventilation Goals

• Oxygenation / Ventilation
• Minimise toxicity - Barotrauma /
  volutrauma - Oxygen toxicity - Negative
  impact on CV system
• Optimise patient work of breathing
• Maximise patient comfort

80
Weaning

• Stable clinical condition
• Improved compliance
• Improved oxygenation
• Adequate pH/appropriate CO2

81
Weaning

• Facilitate spontaneous breathing
• Promote patient ventilator synchrony
• Appropriate work of breathing for patient

82
Weaning Problems

• Unable to trigger/Auto trigger
• High WOB through narrow tube
• Fixed flow does not meet patient demand
• Inadequate tidal volume
• Collapsed lung
• Intrinsic PEEP

83
Weaning Solutions

• Appropriate trigger sensitivity
• Clinical examination
• Use of graphics
• Titrate support

84
Extubation

• Patient can protect airway and cough
• Respiratory drive
• Oxygenation, compliance and dead space
• Haemodynamic stability