Lung volume and oxygenation changes with a closed suction system (CSS) in patients undergoing volume controlled ventilation (VCV)

We wished to measure changes in lung volume (Δ LV), airway pressures, and oxygenation during tracheal suctioning performed with a CSS and with an open suction system (OSS). We enrolled 7 adult patients, sedated and paralyzed, VCV ventilated by a SERVO 900C ventilator (Siemens, Sweden) with PEEP ≥ 5 cmH₂O and FiO₂ ≥ 0.4. Keeping all remaining ventilarory settings unchanged, we set trigger sensitivity at -2 cmH₂O, inspiratory time at 25%, inspiratory pause at 10%. We performed four suctioning manouvers at 20 min intervals using alternatively a CSS and an OSS. With both systems, we used 12 F size catheters. We performed no pre-oxygenation manouvers. Suction was applied for 20 s at a pressure of 100 cmH₂O. We continuously recorded signals of respiratory inductance pletismography (RIP. Respitrace Plus. NIMS, FL), arterial oxygen saturation (O₂Sat) by pulse oxymetry, and airway pressures. We obtained Δ LV as the change in the RIP signal measured during VCV and during suction. We measured Respiratory Rate (RR), peak inspiratory pressure (PIP), positive end-expiratory pressure (PEEP), and mean airway pressure(MAP) during VCV and during suction with the CSS.

Results

Variables are reported as mean ± DS.

Comment

The use of the OSS resulted in discontinuation of ventilatory support with a loss in lung volume and in O₂Sat. The CSS effectively preserved lung volume and oxygenation by maintaining airway pressures during the suction manouvre. The increase in RR observed with the CSS was due to activation of the trigger mechanism.

Table 1