What is meant by auto mode and variable support or variable-pressure control mode of mechanical ventilation?
Automode and variable support or variable-pressure control mode of mechanical ventilation is an advanced technique that uses both PRVC (pressure-regulated volume-control) and VSV (volume-support ventilation). This mode is designed to automatically switch between PRVC and VSV by getting feedback from the patient's breathing. If the patient is not breathing own his own or if the spontaneous breaths are not there, the mode switches to PRVC. PRVC is an adaptive mode of ventilation that uses feedback mechanism on breath to breath basis to help regulate the inspiratory pressure given to the patient in order to achieve the set tidal volume. However, if the patient spontaneously breathes i.e. takes two consecutive breaths, then the mode switched to VSV. In VSV, the breaths are set off by the patient and these breaths helps regulate the time of inspiration and frequency. If the patient becomes apneic for 12 seconds (adult) or for 8 sec (in child), the VSV mode switches back to PRVC.
