A new closed tracheo-bronchial suction system was evaluated. With this device the patient need not be disconnected from the ventilator during suctioning, and can thus have a continuous supply of oxygen. The closed suction system is attached to the patient's endotracheal tube and ventilator Y-piece. The catheter, which is enveloped by a plastic sheet, can remain connected to the patient for as long as 24 h (Fig. 1). MATERIALS AND METHODS. In the medical and surgical intensive care unit of Alt/Neuötting General District Hospital, 39 trials on 16 mechanically ventilated patients receiving more than 8 cm H2O positive end-expiratory pressure (PEEP) and/or more than 60% FiO2 were performed. Each subject was suctioned using the open and closed methods. Arterial blood gases were obtained through an indwelling catheter before suctioning and then 1, 5, and 15 min after suctioning. Open suctioning: After 2 min preoxygenation with 100% oxygen the patient was disconnected from the ventilator, the suction catheter was inserted and the subject suctioned for a maximum of 15 s, then manually ventilated four times and reconnected. Closed suctioning: After preoxygenation the patient was suctioned without disconnection by means of the closed suction system. Statistical analysis was done by the two-tailed t-test on individual paired differences or by Student's t-test. P values of less than 0.05 were accepted as significant. Patients were subdivided according to the PEEP level used (less or more than 8 cm H2O) and analysed separately. One minute after suctioning (T1) arterial pO2 was found to increase significantly for the open-system method when PEEP ventilation was < or = 8 cm H2O (Table 1) and for the closed system method when PEEP ventilation was both < or = 8 cm H2O (Table 1) and > 8 cm H2O (Table 2). Five (T5) and 15 (T15) min after suctioning, pO2 dropped significantly compared to baseline values in the open-system method when PEEP was > 8 cm H2O (Table 2). PO2 values 15 min after closed suctioning with PEEP > 8 cm H2O were significantly higher than those after open suctioning (Table 2). After the pO2 differences were formed between baseline and values 1, 5, and 15 min after suctioning, significant differences between open- and closed-system suctioning were found for PEEP > 8 cm H2O at T1, T5, and T15 (Table 2, Fig. 3). DISCUSSION. The increase in pO2 as a positive effect of preoxygenation with 100% oxygen before suctioning was less marked for open-system suctioning with PEEP > 8 cm H2O because FiO2, measured at the ventilator Y-piece, was abruptly reduced after disconnection and simultaneously PEEP was lost. As a consequence, pO2 values fell significantly 5 and 15 min after suctioning in this situation, whereas for all the other conditions pO2 reached baseline as well as slightly higher values. Patients with severe respiratory insufficiency need continuous positive airway pressure to keep unstable alveoli patent. Every maneuver that reduces intra-alveolar pressure may precipitate alveolar collapse. However, in the diseased lung closed alveoli may not re-expand at once when pressure is re-established. Therefore, closed-system suctioning may help to prevent prolonged deterioration of oxygenation in patients with severe respiratory failure.

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