2. Ventilatory strategies in the ICU
Need for mechanical ventilation
Modes of ventilation – VCV, PCV, DCV
Invasive vs Noninvasive ventilation
Weaning from mechanical ventilation
Extubation and failure to extubate
5. “Inability to maintain either the normal
delivery of O2 to the tissues ± removal of
CO2 from the tissues”
Type I vs Type II
Respiratory failure
6. INDICATIONS FOR MECHANICAL VENTILATION
• Ventilation abnormalities - Respiratory muscle dysfunction
Respiratory muscle fatigue
Chest wall abnormalities
Neuromuscular disease
Decreased ventilatory drive
Increased airway resistance
• Oxygenation abnormalities - Refractory hypoxaemia
Need for PEEP
Excessive work of breathing
7. INDICATIONS FOR MECHANICAL VENTILATION
• Need for anaesthesia, sedation and/or
neuromuscular blockade
• Need to decrease systemic/myocardial
oxygen consumption, e.g., low cardiac
output states
• Use of hyperventilation to reduce
intracranial pressure
8. Oxygen delivery
Adequate alveolar ventilation
Restore acid-base balance
Reduce work of breathing
Minimal side-effects
Goals of ventilatory support
9. Ventilatory strategies in the ICU
Need for mechanical ventilation
Modes of ventilation – VCV, PCV, DCV
16. Volume controlled vs Pressure controlled modes
COMPARISON VCV PCV
Volume Constant Varies
Effect of low
compliance
Higher pressure Lower volume
Effect of high
airway resistance
Higher pressure Lower volume
Peak airway
pressure
High Lower
Mean airway
pressure
Lower Higher
17. Case scenario 1
A 30 year old man, weighing 50 kg who had
undergone laparotomy the previous day was
complaining of pain at the incision. The
postgraduate prescribed morphine 50 mg and
phenergan 12.5 mg IM. The injections were given.
Fifteen minutes later, he becomes apnoeic.
18.
19.
20. Case scenario 2
He was nicely settled on ventilator but now seems
to have some respiratory efforts
30. Case scenario 3
By 4 AM, the patient seems to be stable and
breathing a lot better than before. You want
to see whether you can encourage his
spontaneous breaths and wean him by
morning. What mode would you choose?
34. Positive End-Expiratory Pressure (PEEP)
PEEP is not a mode of ventilation per se
0
+
PEEP with Mandatory breaths
Alveolarpressure
Time
5
Baseline variable
35. Continuous Positive Airway Pressure
(CPAP)
Appropriate for patients who have adequate
spontaneous ventilation but persistent
hypoxaemia due to physiological shunting
Pressure
(cmH2O)
0
+
-
Baseline
39. Noninvasive Ventilation – Advantages
Reduced need for sedation
Preservation of airway reflexes
Avoidance of upper airway trauma
Decreased ventilator associated pneumonia
Improved patient comfort
Shorter length of stay in the ICU and hospital
Improved survival
40. Noninvasive Ventilation – Disadvantages
Claustrophobia
Facial/nasal pressure lesions
Unprotected airway
Inability to suction deep airway
Gastric distension with face mask
Delay in intubation
41. Noninvasive Ventilation - Contraindications
Cardiac or respiratory arrest
Haemodynamic instability
Patients unable to co-operate
Inability to protect airway
High risk for aspiration
Active upper GI bleed
Severe hypoxaemia
Facial trauma, surgery or burns
42. Case scenario 4
This patient was doing fine for two days
but developed abdominal distension,
vomited and aspirated. He had to be
reintubated and ventilated. He has stiff
lungs now.
43. Case scenario 4
ABG
FIO2 – 1
PaO2 – 100 mm Hg
PaCO2 – 45 mm Hg
pH – 7.3
SpO2 – 98%
Mode
Frequency
Tidal volume
I:E ratio
FIO2
59. Case Scenario 5
A 20 year old man, known asthmatic, was
admitted to the Casualty with severe wheeze.
He is tachypnoeic, hypoxic and restless. He
was sedated and intubated but his lungs are
very stiff. What would you do?
60. Case scenario 5
Mode - PCV
Frequency - Slower
Tidal volume – 7 ml/kg
I:E ratio – Longer I:E
FIO2
ABG
FIO2 – 1
PaO2 – 250 mm Hg
PaCO2 – 50 mm Hg
pH – 7.3
64. Ventilatory strategies in the ICU
Need for mechanical ventilation
Modes of ventilation – VCV, PCV, DCV
Noninvasive ventilation
Weaning from mechanical ventilation
72. Rapid shallow breathing index
(RSBI) *
* Yang KL, Tobin MJ. N Engl J Med 1991,324:1445-50
f / VT < 105 (b.min-1L-1)
Where,
f = Respiratory rate in
breaths.min-1
VT = Tidal volume in Litres
80. The most common cause of
failure to wean is an
imbalance between
ventilatory capability and
ventilatory demand.
81. Patients who fail an SBT should
receive a stable, nonfatiguing,
comfortable form of ventilation
Attempts at weaning can continue
with once daily SBTs.
Twice daily SBTs offer no
advantage over once daily SBT.
82. Ventilatory strategies in the ICU
Need for mechanical ventilation
Modes of ventilation – VCV, PCV, DCV
Noninvasive ventilation
Weaning from mechanical ventilation
Extubation and failure to extubate
83. The decision to discontinue
ventilatory support
must be distinct from the
decision to extubate !
84. Those who will be successfully
extubated will have
i) the resolution of the disease
ii) haemodynamic stability
iii) absence of sepsis
iv) adequate oxygenation status
v) adequate ventilatory status…. etc,
etc
85. and also will have….
the ability to maintain
patency of the airway
86. Upper airway obstruction
Excess respiratory secretions
Inability to protect airway
Cardiac failure or ischaemia
Encephalopathy
Respiratory failure
GI bleeding, sepsis, seizures
Causes of
failure to
extubate
87. Maziak DE, Meade MO, Todd RJ. Chest 1998;114:605-9
Insufficient evidence exists to support the
idea that the timing of tracheotomy alters
the duration of mechanical ventilation in
critically ill patients.
ROLE OF TRACHEOSTOMY IN
WEANING
88. Ventilatory strategies in the ICU
Need for mechanical ventilation
Modes of ventilation – VCV, PCV, DCV
Noninvasive ventilation
Weaning from mechanical ventilation
Extubation and failure to extubate
