Each company donated the needed test samples from everyday stock supplies. Five catheters of each type were tested.
Flow Measurement: A bench set-up was created as in Figure 2. As with the PDUs, flow measurements were obtained using the RT 200 Calibration Analyzer. Measurements were made four months after the last calibration.
The Pleur-evac A-6000 (Deknatel) PDU with — 60 mm Hg of applied wall suction was used for testing of all catheter sets. The Pleur-evac A-6000 was chosen given its combination of suction accuracy and high flow rates, particularly at — 20 cm H2O, accommodated in a dry unit. A water column unit was not chosen given the potential of variability in the water column height during testing of each PDC group. Source
The testing apparatus consisted of a large carboy connected to the RT 200 Calibration Analyzer, which was then connected in serial to the PDU through which suction was applied. All connections were with rigid tubing with elastic foam sealant tape at all joints to prevent air leaks. The catheters themselves were placed in adjustable adapters supplied by Cook and sealed with silicon caulk. The catheter/adapter assembly was inserted into a large rubber cork, and the cork was inserted into the carboy for testing purposes.
The RT 200 Calibration Analyzer was set at BTPS and “zeroed” prior to testing of each catheter. Three pressure settings (— 10 cm H2O, — 20 cm H2O, and — 40 cm H2O) were used during testing, and each catheter was occluded prior to each measurement while under suction to ensure the absence of leaks in the apparatus (0 L/min of flow). The catheters in a specific set were all tested at the same negative pressure to decrease the chances for variability. Negative pressures were increased sequentially, and testing of all catheters in each set was completed.
Figure 2. The set-up to measure PDC flow. Shown (left to right), sequentially connected, are the PDU (Pleur-evac A-6000), the RT-200 Calibration Analyzer, and a carboy with a PDC seated in its top opening.