Volume control-intermittent mandatory ventilation (VC-IMV) versus pressure control-continuous spontaneous ventilation (PC-CSV)

A) Changes in pressure-time product (PTP) per minute, B) PTP per breath, and C) frequency as volume control-intermittent mandatory ventilation (VC-IMV) and pressure control-continuous spontaneous ventilation (PC-CSV; previously known as pressure support) were progressively increased. PC-CSV of 100 percent represents the level necessary to achieve a tidal volume equivalent to that during VC-IMV (10 mL/kg); VC-IMV of 100 percent is the same ventilator rate as during VC-IMV. From zero assistance to 60 percent, decrease in PTP/min was greater with PS than with VC-IMV. From 60 to 100 percent assistance, the opposite was observed; the decrease in PTP/min was greater with VC-IMV than with PV-CSV. PTP per breath decreased linearly as the rate of VC-IMV was increased to 60 percent. PTP per breath decreased linearly as the amount of PC-CSV was increased to 60 percent, but little thereafter. Frequency decreased linearly as PC-CSV was increased. In contrast, frequency changed little as the rate of VC-IMV was increased, until a high level of assistance was provided.