Target Alveolar Ventilation - ResMed Astral Series Clinical Manual

Ventilation modes

Target alveolar ventilation

iVAPS targets alveolar ventilation. Alveolar ventilation was chosen because gas exchange occurs at the
alveoli level. Total ventilation includes the ventilation devoted to the conducting airways, whereas
alveolar ventilation best represents the useful portion of ventilation that reaches the alveoli.
Alveolar ventilation cannot be measured directly, so iVAPS estimates it using a height approximated
value of anatomical deadspace as shown in the graph below. Anatomic deadspace is the amount of
breath that remains in the conducting airways, that does not reach alveoli and does not contribute to gas
exchange. Its contribution is proportional to breath rate. By using alveolar ventilation as a
servo-ventilation target, as opposed to tidal volume or minute ventilation, the effect of respiratory rate
change on effective ventilation is compensated for.
Note: When ventilating in iVAPS mode, the current Va value is displayed on the Monitoring screen.
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