Mechanical Ventilator

Question 1

Advantages of negative pressure ventilation

Answer 1

Decreased risks of pneumonia.
Decreased need for sedation.
Less decrease in cardiac output.
More comfortable.
Cheaper than positive pressure ventilation.
Easy to wean.

Question 2

Disadvantages of negative pressure ventilation

Answer 2

Difficult to suction
Inability to generate high intrapulmonary pressures.
Limited access to patients body
Contraindicated where it is not possible to maintain upper airway.
Increased risks of pressure sores.

Question 3

Dynamic compliance VS static compliance

Answer 3

Dynamic compliance:

• measures resistance of airways.
• it measure using peak inspiratory pressure
• is influenced by bronchospasm, blockage of airways and airway compression.
• dynamic compliance = expiratory tidal volume / (peak inspiratory pressure - positive end expiratory pressure)
• normal = 70-100

Static compliance

• measures a true compliance of lung tissue.
• measures with a plateau/pause phase.
• is influenced by parenchymal disease, pulmonary oedema, abnormalities in pleural space and chest wall.
• static compliance = expiratory tidal volume / (pause pressure - positive end expiratory pressure)
• Normal = 50-80.

Low compliance indicate lung stiffness
In advanced COPD static compliance is increased due to loss of elasticity of lung fibres therefore more air is trapped in the lungs.

Question 4

Pressure support

Answer 4

Provide a certain level of pressure to the inspiratory circuit when patient starts to inhale. This boots the patient’s own respiratory efforts by increasing spontaneous tidal volume and unloading patients respiratory muscle

Question 5

Positive end expiratory pressure

Answer 5

A positive pressure added to airways at end of expiration to prevent collapse of alveoli and increase patients tidal volume and functional residual capacity

Question 6

Pressure controlled ventilation

Answer 6

It’s a constant pressure that is delivered to airways with every breath.

Question 7

Volume controlled ventilation

Answer 7

A constant flow is delivered with every breath

Question 8

Synchronized intermittent mandatory ventilation (SIMV)

Answer 8

The machines breaths are coordinated with patients spontaneous respiratory rate.
Used in weaning mode.

Question 9

Continuous positive airway pressure

Answer 9

Patient breaths totally spontaneous and generates their own tidal volume.

Question 10

Complications associated with MV

Answer 10

Absorption atelectasis
Decreases CO and BP
Barotrauma and dynamic hyperinflation.
Diverts blood away from thorax and reduce renal, hepatic and splanchnic blood flow.
V/Q mismatch.
Respiratory muscle atrophy.