Several animal studies have shown that mechanical ventilation with larger
tidal volume (Vt). Volume-trauma rapidly results in pulmonary changes that mimic
ARDS. These studies have also shown that alveolar over distention rather than
peak or plateau pressure seems to be responsible for VALI/VILI.
Absolute trans-pulmonary pressure (alveolar-pleural), rather than peak and
plateau pressure, is responsible for over distention and injury. Peak and plateau
pressure could/are also influenced by the airway resistance and the chest wall
component.
Repeated alveolar collapse and re-expansion (“atelectrauma”) also seems to
play a significant role in the development of VILI/VALI.
III. Modes of mechanical ventilation
Conventional ventilation is by far the most often utilized mode of ventilation.
Other forms of mechanical ventilation include:
- High frequency oscillatory ventilation (HFOV)
- High frequency jet ventilation (HFJV)
- Liquid ventilation
A. Conventional Ventilation
During each breath on conventional ventilation, positive pressure is
generated by the ventilator and airflow is delivered over time (amount of gas deliver
in each breath = tidal volume) to the patient via the endotracheal tube; this is done
at a certain frequency (respiratory rate). As simple as this sound there are several
factors/available choices to consider when starting somebody on conventional
mechanical ventilation: