Mechanical Ventilation

Question 1

What is volume pre-set assist control ventilation?

Answer 1

A mode in which the operator sets a tidal volume and a minimum ventilatory rate, where both the patient and the ventilator are able to initiate breaths.

Question 2

What are the advantages of volume pre-set assist control ventilation?

Answer 2

Simple to set
Guaranteed minute ventilation
Rests muscles of respiration

Question 3

What are the disadvantages of volume pre-set assist control ventilation?

Answer 3

Not synchronised with patient’s breathing

Inappropriate triggering (e.g. as a result of hiccoughs) can result in excessive minute ventilation

Fall in lung compliance results in high alveolar pressure and barotrauma

Question 4

What is pressure pre-set assist control ventilation?

Answer 4

A constant pressure is applied during inspiration.

This results in a high initial flow until the pressure is reached, at which point the flow slows and stops.

Question 5

What is the advantage of pressure pre-set assist control ventilation?

Answer 5

Oxygenation may be better due to the flow pattern (initial high rate of flow)

Avoids high inspiratory pressures.

Question 6

What are the disadvantages of pressure pre-set assist control ventilation?

Answer 6

Not synchronised with the patient’s breathing.

Inappropriate triggering (e.g. due to hiccoughs) can result in excessive minute ventilation.

Change in lung compliance can result in a change in tidal volume.