Principles of Mechanical Ventilation

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Principles of Mechanical Ventilation
Initial Ventilatory Settings

• Mazen Kherallah, M.D., FCCP
• Internal Medicine, Critical Care Medicine, and
  Infectious Diseases

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Modes of Mechanical Ventilation
Volume-Cycled Control Mode Ventilation
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Volume-Cycled Control Mode Ventilation

• Indicated for patients who are unable to
  ventilate
• Drug intoxication
• CNS disorders
• Peripheral neurological disorders
• Pharmacological Paralysis

• Limitations
• Patient-ventilator dysynchrony secondary to
  aborted ventilatory cycles when patient exhales
  during ventilator inspiratory cycle
• Hypercapnea

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Modes of Mechanical Ventilation
Assist-Control Ventilation
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Assist-Control Ventilation

• Indications
• for patients who are awake, moderately sedated
  or paralyzed and able to initiates ventilation
• increase metabolic demands infection, burns,
  multisystem organ failure
• Respiratory muscle strengthening and weaning

• Limitations
• patient-ventilator dysynchrony
• ventilator assisted hyperventilation in agitated
  patients with increased inspiratory drive
• auto-PEEP in COPD patients

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Modes of Mechanical Ventilation
Intermittent Mandatory Ventilation
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Modes of Mechanical Ventilation
Synchronized Intermittent Mandatory Ventilation
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Synchronized Intermittent Mandatory Ventilation

• Indications
• patients with minimal spontaneous respiratory
  efforts
• respiratory muscle conditioning
• ventilator weaning

• Limitations
• patient-ventilator dysynchrony especially in
  agitated patients
• nonphysiologic way of respiratory muscle
  conditioning

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Modes of Mechanical Ventilation
Pressure Support Ventilation
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Pressure Support Ventilation

• Indications
• weaning
• more physiologic conditioning of respiratory
  muscles low pressure-high volume load
• improved patient-ventilator dysynchrony

• Limitations

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Modes of Mechanical Ventilation
Inverse Ratio Ventilation
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Distribution of Normal Ventilation-Perfusion
Ratios
1
10
0.1
0

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Oxygen-carbon dioxide diagram
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The Effect of Increasing Ventilation-Perfusion
Inequality on Arterial Po2 and Pco2
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Ventilation-Perfusion Inequality
Acute Exacerbation of COPD
0 .01 0.1
1 10 100
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Ventilation-Perfusion Inequality
Asthma
0 .01 0.1 1
10 100
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Ventilation-Perfusion Inequality
Pulmonary Embolism
0 .01 0.1 1
10 100
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Shunting Process
ARDS
0 .01 1
10 100
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The effect of changing the inspired oxygen
concentration on arterial Po2 for lungs shunts
of 10 to 50
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Pulmonary Mechanics
Peak pressure
Airway Resistance
Plateau pressure
I
E
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Static Pressure-volume curve in ARDS with PEEP of
0 and 12
12 PEEP
0 PEEP
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Auto-PEEP
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Auto-PEEP
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Normal Lung Mechanics and Gas Exchange
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Severe Airflow Obstruction
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Acute on Chronic Respiratory Failure
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Acute Hypoxemic Respiratory Failure