Introduction
Removal of pulmonary secretions in mechanically ventilated patients usually requires suction with closed catheter systems (closed-circuit suctioning) or flexible bronchoscopes. If the suction device obstructs larger parts of the endotracheal tube (ETT) lumen, ventilation volumes and ventilator circuit pressures may change dramatically. Under such conditions, concerned personnel may switch to ventilation with a self-expanding bag with the intention to maintain adequate ventilation—in spite of current guidelines that recommend the ventilator to be connected during suction procedures.1 An alternative strategy, if copious secretions cannot be adequately eliminated during closed catheter suctioning, is to disconnect the ETT from the ventilator in order to more effectively remove airway secretions through an open suction procedure.2 Manual hyperinflation is also a frequently used manoeuvre that intends to mimic a forceful cough in critically ill intubated and mechanically ventilated patients.3
In previous lung model and animal studies of open and closed endotracheal suctioning, Stenqvist and colleagues have found that closed system suctioning may cause subatmospheric pressures in the lungs,4 and have shown that open and closed system suctioning at atmospheric pressure (continuous positive airway pressure (CPAP), 0 cm H2O) is more effective than closed system suctioning during pressure-controlled ventilation (PCV) and CPAP 10 cm H2O.5 They also found that frequent drug inhalation and endotracheal suctioning predispose to de-recruitment of the lungs,6 and that volume-controlled ventilation (VCV) can be used to rapidly restitute lung aeration and oxygenation after lung collapse induced by open suctioning.7
We have previously reported on the effects of ETT device insertion and suctioning on airway pressures in a lung model during pressure-controlled and volume-controlled mechanical ventilation.8 For comparison, we now investigated how suctioning during manual ventilation and during ETT disconnection affected airway pressures in the same model. Our main hypotheses were that endotracheal suctioning during manual ventilation creates pressure reductions similar to those seen in mechanical ventilation with volume-controlled mode, and that suctioning with the ETT disconnected from the bag/ventilator (open suction procedure) provides even more negative pressures distal to the ETT.