Effects of flow triggering on breathing effort during partial ventilatory support

Area of Science:

• Mechanical Ventilation
• Respiratory Physiology
• Critical Care Medicine

Background:

• Discrepant results exist regarding the impact of flow triggering (FT) versus pressure triggering (PT) on breathing effort.
• Understanding these differences is crucial for optimizing ventilator settings and patient comfort.

Purpose of the Study:

• To compare the breathing effort associated with FT and PT across different ventilator modes.
• To investigate the influence of ventilator sensitivity settings on triggering effort.

Main Methods:

• A lung model quantified triggering effort (airway pressure-time product, PTPaw) for various sensitivity settings on nine ventilators.
• A comparative clinical study in eight ventilator-dependent patients assessed FT versus PT during pressure-support ventilation (PSV) and volume-targeted assist-control ventilation (ACV).
• Breathing effort was measured using esophageal pressure-time product (PTPes/min), transdiaphragmatic pressure-time product (PTPdi/min), and inspiratory work of breathing per minute (Wi/min).

Main Results:

• Bench study showed significant differences in PTPaw between ventilators; FT reduced PTPaw compared to PT in two of three ventilators tested.
• Clinical study demonstrated significant reductions in PTPdi/min (16%), PTPes/min (13%), and Wi/min (14%) with FT versus PT during PSV.
• No significant differences in breathing effort were observed between FT and PT during ACV.

Conclusions:

• Flow triggering (FT) more effectively reduces patient breathing effort than pressure triggering (PT) when used with pressure-targeted modes like PSV.
• The observed differences are attributed to variations in the post-trigger phase, impacting overall breathing effort.
• FT's benefit on breathing effort is mode-dependent, being more pronounced in pressure-targeted ventilation compared to volume-targeted ventilation.