The effect of targeting scheme on tidal volume delivery during volume control mechanical ventilation

Technological advances have increased ventilator mode complexity and risk of operator error.

To compare differences in volume control (VC) ventilation with set-point and dual targeting. Two hypotheses were tested: tidal volume (V(T)) delivery is different with VC using set-point versus dual targeting during active versus passive breathing; VC with dual targeting delivers V(T) similar to pressure support ventilation (PS) with active breathing.

The Ingmar Medical ASL 5000 lung model simulated pulmonary mechanics of an adult patient with ARDS during active and passive ventilation. Resistance was standardized at 10 cm H(2)O/L/s and compliance at 32 mL/cm H(2)O. Active breathing was simulated by setting the frequency (f) = 26 breaths/min, and adjusting the muscle pressure (P(mus)) to produce a V(T) of 384 mL. VC was initiated with the Puritan Bennett 840 (set-point targeting) and the Servo-i (dual targeting) at V(T) = 430 mL, mandatory f = 15 breaths/min, and PEEP = 10 cm H(2)O. During PS, cycle threshold was set to 30% and peak inspiratory pressure adjusted to produce a V(T) similar to that delivered during VC. Expiratory V(T) was collected on 10 consecutive breaths during active and passive breathing with VC and PS. Mean V(T) differences (active vs passive model) were compared using analysis of variance. Statistical significance was established at P < .05.

The mean ± SD V(T) difference varied with targeting schemes: VC set-point = 37.3 ± 3.5 mL, VC-dual = 77.1 ± 3.3 mL, and PS = 406.1 ± 1.5 mL (P < .001). Auto-triggering occurred during VC set-point with the active model.

Dual targeting during VC allows increased V(T), compared to set-point, but not as much as PS.