Patient-ventilator interaction during synchronized intermittent mandatory ventilation. Effects of flow triggering

Area of Science:

• Critical Care Medicine
• Respiratory Therapy
• Mechanical Ventilation

Background:

• Synchronized intermittent mandatory ventilation (SIMV) combines assisted and spontaneous breaths.
• The effectiveness of SIMV as a weaning strategy is debated due to limited patient adaptation to ventilator support.

Purpose of the Study:

• To investigate inspiratory effort and patient-ventilator interaction with flow-triggered versus pressure-triggered SIMV.
• To compare different levels of SIMV support (100%, 50%, 0%) during the weaning process.

Main Methods:

• Evaluated flow-triggered and pressure-triggered SIMV in patients undergoing weaning.
• Measured inspiratory effort using esophageal pressure time product per breath (PTP/b) and per minute (PTP/min).
• Assessed both mandatory and spontaneous breaths under constant flow and constant pressure conditions.

Main Results:

• Flow triggering significantly reduced PTP/b and PTP/min for both mandatory and spontaneous breaths compared to pressure triggering.
• During pressure-triggered SIMV, PTP/b and PTP/min were similar for mandatory and spontaneous breaths.
• Flow-triggered SIMV showed lower PTP/b and PTP/min for mandatory breaths than spontaneous breaths, especially with constant pressure ventilation.

Conclusions:

• Flow triggering enhances patient-ventilator interaction during SIMV.
• This method reduces inspiratory effort in both mandatory and spontaneous breaths, aiding ventilator weaning.
• Flow triggering appears to be a superior method for improving patient adaptation during SIMV weaning.