what is relavance of dead space in mechanical ventilator

Airway pressure was measured close to the pneumotachograph by using a differential pressure transducer (MP45, ☑00 cm H 2O Validyne, Northridge, CA). The air flow rate was measured using a heated and calibrated pneumotachograph (Fleisch #1 Fleisch, Lausanne, Switzerland) that was linear over the experimental flow range. Time constant is monitored continuously, and a change in MV can by itself induce a change in the time constant and subsequently in the target VT.Īll measurements were performed during the last 5 min of the three ventilatory modes that were randomized with dead space on and off for each, i.e. , six following study periods: PSV-dead space off, PSV-dead space on, APV-dead space off, APV-dead space on, ASV-dead space off, ASV-dead space on.

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.

What is relavance of dead space in mechanical ventilator