Warning! Suctioning. A lung model evaluation of closed suctioning systems

Background: Closed system suctioning, CSS, has been advocated to avoid alve olar collapse. However, ventilator manufacturers indicate that extreme nega tive pressure levels can be obtained during closed system suctioning, imped ing the performance of the ventilator. Methods: Suctioning with a 12 or 14 Fr catheter with a vacuum level of -50 kPa was either performed with an open technology or a CSS, where the cathet er is introduced through a tight-fitting connection through the endotrachea l tube, ETT. The lung model was ventilated with a Servo 900C or 300 ventila tor with an I:E ratio of 1:2, 1:1 and 2:1 and extrinsic positive end-expira tory pressure (PEEP) at 0 or 10 cm H2O. Respiratory volumes and alveolar pr essure were measured at the lung model alveolus. Results: The initial suctioning flow was >40 l/min with a. 14 Pr catheter. When inserting the catheter through a no. 7 ETT, PEEP rose from 11 to 23 cm H2O during volume control ventilation with an I:E ratio 1:1. During suctio ning the alveolar pressure fell to 10 cm H2O below the set PEEP level. CSS during pressure control ventilation had fewer effects. Low tidal volumes, i nverse I:E ratio and secretions in the tube resulted in pressures down to - 92 cm H2O. Conclusion: CSS should not be used in volume control ventilation due to ris k of high intrinsic PEEP levels at insertion of the catheter and extreme ne gative pressures during suctioning. Pressure control ventilation produces l ess intrinsic PEEP effect. The continuous positive airway pressure (CPAP) m ode offers the least intrinsic PEEP during insertion of the catheter and le ast sub-atmospheric pressure during suctioning.