6. Conditions Associated with Decreased
Total Respiratory Compliance
Decreased Lung compliance
Fall in FRC
• ARDS
• Diffuse Pneumonitis
• Pulmonary Edema
• Atelectasis
Decreased Chest wall
comp.
• Abdominal distension
• Chest wall edema
• Chest trauma/ surgery
Over-expansion of lung volume
• Asthma
• Bronchiolitis
• Excessive CPAP/PEEP
7. “The Feature of the Tube”
Airway Resistance
Pressure Difference = Flow Rate x Resistance of the Tube
Resistance is the amount of pressure required to deliver a given flow of
gas and is expressed in terms of a change in pressure divided by flow.
R = Δ P
Flow
P1 P2
8.
9. Goals of mechanical ventilation
❖ To provide adequate ventilation and oxygenation with
minimal intervention
❖ Minimize the risk of lung injury
❖ Reduce patient work of breathing (WOB)
❖ Optimize patient comfort
10. What we expect from a Ventilator ?
• Ventiltor must recognise patient’s respiratory
efforts.(trigger)
• Ventilator must be able to meet patient’s
demand(response)
• Ventilator must not interfere with patient’s
effort.(synchrony)
11. To understand a ventilator breath cycle, we must know how the
ventilatory breath starts, sustains, and stops inspiration and
maintain expiration
MX-0776 Rev03 Page 11
Inspiration
Expiration
1)Starting of Inspiration or Trigger
start of
Inspiration
End of
Inspiration and
start of
Expiration
3) The end of inspiration or Cycle
2) Inspiration itself or Limit
2) Expiration or Baseline
19. • Transition point from the inspiratory phase to the expiratory phase
Cycling = Expiratory Trigger
MX-0776 Rev03 Page 19
Modes
Trigger
variable
Limit
variable
Cycle
Volume
targeted
Pressure,
flow or time
Volume
Set inspiratory
time
Pressure
targeted
Pressure,
flow or time
Pressure
Set inspiratory
time
Pressure
support
Pressure or
flow
pressure Flow cycle
20. • A mode of mechanical ventilation may be defined, in general,
as a predetermined pattern of patient-ventilator interaction
What Is a Mode of Mechanical Ventilation?
CMV
IMV
Assist
Cont.
SIMV
Mode
Set-Point,
Dual
mode,
Servo
Optimal
Volume,
pressure
Ventilator
Breath Control
Variable
Breath
Sequence
Targeting
Scheme (method
of feed back)
22. Control Mandatory Ventilation
⮚ Breaths are delivered either as
preset volume or pressure
⮚ Cycling occurs when the preset
volume, pressure (or time) is
achieved
⮚ Patient spontaneous breaths not
allowed.
⮚ Used in theatre and in very
unwell ICU patients -heavily
sedated or completely paralysed.
23. Intermittent Mandatory Ventilation (IMV)
• Ventilator Delivers preset time
triggered mandatory breaths
• Patient is allowed to take
spontaneous breath without any
support.
• Advantage
• Less sedation
• Less haemodynamic instability
• More patient Comort
• Disadvantage -
• Breath Stacking - Barotrauma
24. Assist Control
• Ventilator delivers a fully
supported breath whether time or
patient triggered.
• Patient is able to trigger the start
of inspiration
• Trigger – Time/Flow/Pressure
• Limit – Pressure/Flow
• Cycle – Time
25.
26. SIMV
• The ventilator attempts to synchronize the
delivery of mandatory breaths with the
spontaneous efforts of the patient.
• Breaths are time triggered but synchronized
with patients effort
• However, when the breath is patient
triggered, the ventilator delivers a pressure-
supported breath (at a level set by the
clinician).
30. PSV/CPAP
• Patient triggered (flow/pressure)
• Flow cycled
• Respiratory Rate is controlled by
patient
• PS to set to achieve TV 5-6 ml/kg
• Weaning Mode
• TV is variable
• Set back up ventilation
32. Dual Control MODE
• PRVC: Pressure Regulated Volume Control
• Basically pressure control mode
• Flow decelerating type
• Fixed tidal volume is ensured
• Ventilator uses a feedback method on a
breath-to-breath basis, to continuously adjust
the pressure delivered to achieve the tidal
volume target
33.
34.
35. Volume Guarantee: New Approaches in Volume Controlled Ventilation for Neonates. Ahluwalia J,
Morley C, Wahle G. Dräger Medizintechnik GmbH. ISBN 3-926762-42-X
Ventilator Parameters
36. Tidal Volume
Tidal volumes should be 3–6 mL/kg predicted body weight for
patients ARDS
Physiologic range (5–8 mL/kg ideal body weight) for patients with
normal lung
Tidal volumes should be 8–10 mL/kg predicted body weight for
patients neurological disorder
37. Pressure
• PIP
• Platue Pressure
HOW MUCH ?
Assess bedside while bagging
Mild - 10 -12 cmH2o
Moderate - 15-18 cmH2o
Severe – 18-20 cmH2o
Inspiratory plateau pressure limit of 28 cm H2 O
Slightly higher plateau pressures (29–32 cm H2 O) for patients with
increased chest wall elastance .
38. Total pressure = frictional forces (Resistance)
+ Elastic recoil of lungs and chest wall
39. P plat and PIP
P plat is measured by inspiratory hold for 4-5 sec.
42. Optimizing PEEP
HELPS:
• Recruits, reduces oxygen requirements
• Helps to take the lung to the better part of
compliance
• Prevents atelecto-trauma
ADVERSE:
• Excess PEEP causes decreased venous return
• Hypotension
• Baro trauma
43. How much PEEP to start with ?
• Moderate to Severe ARDS – 8-10 cmH2O
• Asthma/Bonchiolitis – 3-5 cmH2O
• Raised ICP – 4-5 cmH2O
• Cardiogenic Pulmonary Edema – 6-8 cmH2O
44. • 60 sec
Total breath Time = ــــــــــــــــــــــــــــــــــــ
Breath Rate
Example Rate = 30 , Total time 60/30 = 2 sec.
If I:E ratio - 1:2 ------then
Ti = 0.66 so , TE = 1.33 sec
• Primarily effects MAP and oxygenation
• Inverse ratio (1:1) – used in ARDS.
• Prolonged expiratory rates (1:3 or 1:4) – Spasm of small airway
Short Ti-inadequate Oxygenation
Short Te- inadequate CO2 out leads auto PEEP
I:E Ratio (Inspiratory-Expiratory ratio)
45. Actual I Time setting
• Inspiratory time needs to reflect the age of the child.
• Typically for newborns - 0.5 seconds
• 1 year age - 0.8 seconds
• >2 years it is - 1 second, which if needed, can go up to
1.2 seconds
46. Basic setting of Ventilator in PICU
• Choice of ventilator mode: control ? Support/assist?
• AC Mode – Severe ARDS, Comatose child, Neuroprotection,
Cardiogenic schock ,
• SIMV + PS – Pneumonia, Bronchiolitis , Asthma
• Start all parameters at normal physiological demand and change
accordingly
1. FiO2: 50-60 %, or 100 % .target SO2 >94-95, PaO2 60-80, Hypo &
hyper oxaemia act as double edged sword
2. PIP: 15 - 18, assessed by BAE, chest rise, VT, RD & SO2
3. PEEP: low-3-4, medium 5-8, high 8-15
4. RR: normal physiological rate, <1yr 30-35, 1-5 yr, 25-30/min
47. What is the most effective way of
improving oxygenation in ARDS ?
A.Optimize PEEP
B. Increase FiO2
C. Increase PIP
D.Increase Inspiratory time (Ti)
48. In Assist control VC mode which one is
false ?
• Patient can trigger breath
• TV will be same for all breath
• PIP and Pplat are different
• In ARDS PIP requirement increases but Pplat
remains same
• Target Pplat in ARDS – 28 - 30
49. In SIMV + PS Mode all are true except
• Patient triggered breaths are supported
• For patient triggered breath cycling is Time
• TV/PIP is same for all beath
• It can be weaning mode
