![]() ![]() The patient-desired MV is not part of the loop. The target VT is defined by the clinician-set MV and the calculated time constant. Conversely, ASV is more sophisticated than a “simple” dual mode, because of the moving RR-VT target according to change in respiratory mechanics, 9,10because of the control of MV that prevents alveolar hypoventilation, and because of a set of rules designed to avoid dead space ventilation, risk of barotraumas, or excessive dynamic hyperinflation. Considering actively breathing patients ASV is adjusting the Pinsp like a dual-control mode in case of increased respiratory demand, a similar response could be expected ( table 1). Thus, the RR is usually also indirectly modified by the ventilatory setting, although not strictly controlled. 9–11The usual patient response to an increased VT is a decrease in RR, and vice versa . In patients able to trigger a breath (active patients), the ventilator generates pressure support breaths, automatically adjusting Pinsp to achieve the target VT, and it delivers additional pressure-controlled breaths if the patient’s RR is below the target RR. ![]()
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