7. Invasive support
Advanced
Ventilation
Tracheostomy
Prone Position
Nitric Oxide
Weaning
Standard
Ventilation
Optimising the
Pt for weaning
Suctioning
Long Term
Weaning/Individual
plan
Weaning
Screen/standard
protocol
Intubation
Humidification
Wake, Warm
& Wean
Non-Invasive
Ventilation
Oxygen
Therapy
Mask CPAP
Non-invasive support
Extubation
Decannulation
8. NIV vs. Invasive Mechanical Ventilation
• NIV is defined as ventilatory support provided via a
tight fitting mask or similar interface as opposed to
invasive support, which is provided via a laryngeal
mask, endotracheal tube or tracheostomy tube.
• Tight fitting masks deliver can CPAP, BIPAP or NIV
via the mechanical ventilator.
9. Indications for Mechanical Ventilation
• The work of breathing usually accounts for 5% of
oxygen consumption (V02).
• In the critically ill patient this may rise to 30%.
• Invasive mechanical ventilation eliminates the
metabolic cost of breathing.
10. Indications for Mechanical Ventilation
• Inadequate oxygenation (not corrected by supplemental O2
by mask).
• Inadequate ventilation (increased PaCO2).
• Retention of pulmonary secretions (bronchial toilet).
• Airway protection (obtunded patient, depressed gag
reflex).
12. Bare Essentials for Intubation
ALSOBLEED
1 Airway: oral Guedel airway to lift tongue off posterior
pharynx to facilitate mask ventilation during pre-intubation
phase.
2 Liquids: stop feed and aspirate ng tube.
3 Suction: extremely important to avoid pulmonary
aspiration.
4 Oxygen: preoxygenate patient and ensure a source of O2
with a delivery mechanism (ambu-bag and mask) is available.
13. Bare Essentials for Intubation
ALSOBLEED
5 Bougie: to facilitate tube insertion in more difficult airway.
6 Laryngoscope: have a long and short blade available.
7 Endotracheal tube: for average adult, cuffed oral
endotracheal tube 7.0 for women and 8.0 for men.
8 End tidal CO2: to confirm correct position of tube.
9 Drugs: an induction agent, muscle relaxant, sedative are
usually required.
15. Principles of Mechanical Ventilation
• Positive pressure ventilation involves delivering a
mechanically generated ‘breath’ to get O2 in and CO2 out.
• Gas is pumped in during inspiration (Ti) and the patient
passively expires during expiration (Te).
• The sum of Ti and Te is the respiratory cycle or ‘breath’.
17. Principles of Mechanical Ventilation
• In the fully ventilated patient, positive pressure breaths
are delivered either as preset volume or pressure
continuous mandatory breaths (CMV) breaths.
• The mechanical ventilator triggers the breath and
switches from inspiration to expiration when the preset
volume, pressure (or time) is achieved/delivered.
• During CMV the patient takes no spontaneous breaths.
• CMV is usually used in theatre and in very unwell ICU
patients.
18. Principles of Mechanical Ventilation
Volume control
Pressure control
• Tidal volume is preset
• Inspiratory Pressure is preset
• Usually 500 mls
• Usually 15-20 cm H20
• Airway Pressure is Variable
• Tidal Volume is Variable
19. Principles of Mechanical Ventilation
• Mandatory breaths are delivered during inspiration, to
generate a tidal volume (Vt), at a set rate (f), the quotient
of which is the minute volume (MV).
• Minute Volume = Tidal Volume x frequency
• In volume control ventilation, an inspiratory flow rate is
also set.
• The ratio of the time spent in inspiration:expiration (I:E
ratio) is usually 1:2.
20. Principles of Mechanical Ventilation
Pressure Control Breath
Flow
Pressure
Volume Control Breath
Ti
Te
Ti
Te
21. Principles of Mechanical Ventilation
• Mechanically ventilated patients usually receive positive
end-expiratory pressure (PEEP), to overcome the loss of
physiological PEEP provided by the larynx and vocal
cords.
• PEEP is delivered throughout the respiratory cycle and
is synonymous to CPAP, but in the intubated patient.
• Standard PEEP setting is 5 cm H20.
• Sedation is often required to prevent ventilator-patient
asynchrony.
22. Basic Settings on the Ventilator
• Tidal Volume
Pressure controlled breath (15-20 cm H20)
Volume controlled breath (500 mls)
• Rate (frequency) (10-12 breaths/minute)
• Positive end expiratory pressure (PEEP) (5 cm H20)
• FiO2 (0.21-1)
• Peak airway pressure (PAP)
23. Principles of Mechanical Ventilation
• Why is the peak airway pressure (PAP) important?
• Ventilator Induced Lung Injury (VILI).
• Mechanical ventilation is injurious to the lung.
• Aim PAP< 35 cm H20.
24. Principles of Mechanical Ventilation
Volume Breath
Pressure Breath
Flow
Pressure
35 cm H20
Ti
Te
Ti
Te
26. Principles of Mechanical Ventilation
Don’t forget that the peak airway pressure
will also include the PEEP that is added
27. Principles of Mechanical Ventilation
• Once stabilised on CMV, the level of ventilatory support
may be reduced (weaning).
• This can be done by providing a mixture of synchronised
intermittent mandatory breaths (SIMV) and spontaneously
triggered pressure supported breaths (PSV).
28. Principles of Mechanical Ventilation
• Ventilator assisted breaths are synchronized with the
patient’s breathing to prevent the possibility of a
mechanical breath on top of a spontaneous breath.
• However, the patient’s attempt at a breath would not be
enough to generate an adequate tidal volume on its own,
hence the term ‘pressure support’.
29. Principles of Mechanical Ventilation
• Pressure support is only delivered during inspiration and
the patient’s attempt at breathing triggers the breath
rather than the ventilator.
• A standard level of pressure support delivered in
inspiration is 20 cm H20
31. Principles of Mechanical Ventilation
• As patients improve, mandatory breaths are
withdrawn and receive pressure-supported breaths
alone.
• Finally, as tidal volumes improve, the level of
pressure support is reduced and then withdrawn so
patients breathe spontaneously with PEEP alone.
• Extubation can now be contemplated.
• Spontaneous modes of breathing should always be
encouraged as respiratory muscle function is
maintained
33. Successful Weaning and Extubation
• To succeed, the initiating cause of respiratory failure,
sepsis, fluid and electrolyte imbalance and nutritional
status should all be treated or optimised.
• Failure to wean is associated with:
• Ongoing high V02.
• Muscle fatigue.
• Inadequate drive.
• Inadequate cardiac reserve.
34. Successful Weaning and Extubation
• Weaning screens exist to help select patients for
extubation.
• In the unsupported patient, if f/Vt is >100, extubation
is likely to be unsuccessful.
• There is some evidence to support extubation to NIV,
particularly in patients with COPD.
35. Basic Ventilatory Modes: Summary
• Continuous Mandatory Ventilation (CMV)
Pressure control
Volume control
No spontaneous breathing
Ventilator triggers breath
• Synchronised intermittent mandatory ventilation
(SIMV)/Pressure Support Ventilation (PSV)
Pressure control (SIMV)
Volume control (SIMV)
Some spontaneous breathing is allowed (PSV)
Mixture of ventilator and patient triggered breaths
36. Basic Ventilatory Modes: Summary
• Pressure Support Ventilation (PSV)
Spontaneous breathing with inspiratory support
All patient triggered breaths
• PEEP/CPAP (5 cm H20)
Entirely spontaneous breathing
Consider extubation
39. Standard Ventilator Settings
MORITE
Mode
CMV, Volume Control
O2
0.5 (50% 02)
Respiratory Rate
12/minute
Inspiratory Action
Set Vt at 500 mls
Inspiratory Time
Set I:E ratio 1:2
Expiratory Action
Set PEEP at 5 cm H20
Be Aware
PAP ≤35 cm H2O
40. Spontaneously Ventilating Patient Failing Conventional Therapy
Consider
CPAP on Ward
Optimise
NIV on ICU
BIPAP
Patient Position
Humidification
BIPAP on Ward
Patient Requiring Basic Invasive Mechanical Ventilation
CMV (VCV or PCV)
Escalation
IMV (VCV or PCV)
PSV
PEEP/CPAP
De-escalation
Notes de l'éditeur
In SIMV mode the ventilator allows two kinds of breath. The first is delivered according to the preset waveform and is the “mandatory breath”. The timing of the start of this breath may be triggered by the patient’s respiratory effort but, if the patient is not making sufficient respiratory effort, is determined by the ventilator. The second is a spontaneous breath. If SIMV is combined with pressure support then the ventilator facilitates this second breath by providing pressure support. This second type of breath is entirely dependent on patient effort.
The graphs illustrate the changes in pressure and flow that occur with first a mandatory breath and then a pressure-supported breath
This slide illustrates the breath to breath variation in the duration of time that the pressure support is provided for and the variable inspiratory flow rates. The latter will depend on the degree of patient effort.
A great variety of ventilatory modes exist and the number of modes is ever increasing. Clearly it is not possible to cover all these modes in one lecture and therefore I will concentrate on the four modes available on the Servo 900C ventilator, a ventilator that is widely used in intensive care