Work Shifting - Mechanical Ventilation

Why the new term:

Synchrony issues, by definition, have to do with timing. Thus, "flow asynchrony" is a misnomer. During inspiration (i.e, the period between trigger and cycle) the main issues are not related to timing but to work of breathing.

Work Shifting: When Pvent and Pmus are active together, some portion of the total work is done by the ventilator and some by the patient.

Explained:

We use pressure, Pvent and Pmus, to demonstrate the relation between the mode of ventilation and the patient. See next page graph. It is the same relationship for pressure as for work. However the term work is more accurate. We can calculate work from the equation of motion. The units are joules or joules per unit of tidal volume (J/L).

We described a Work Shift Index to quantify the amount of work shifted from the ventilator to the patient.

Here depicted:

If patient is on CPAP, with no ventilator assistance, the work by the ventilator W vent is zero and all the work is done by the patient W thus a Work Shifting Index, WS/ = 100%.

See graphic for VC-CMVs and Pmus interactions



Dr. Eduardo Mireles-Cabodevila @emireles_c



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