22 T. Rath et al.: J Extra Corpor Technol 2026, 58, 19 – 31
Figure 2. Data collection protocol. The sequence of data collection at each reservoir level( 200 mL, 500 mL, 1000 mL) was identical. 1. Arterial centrifugal pump flow was set at 4.5 L / min, gas flow 4.5 L / min with 100 % oxygen and arterial temperature was 37C. 2. Suction flow rate was set at 25 RPM( 0.32 L / min) initially with no sucker air injection for a“ no air” verification recording. 3. Sucker air injection was changed to 0.2 L / min, then data was recorded for suction flow rates of 25 RPM( 0.32 L / min) with air, 50 RPM( 0.65 L / min) with air, 75 RPM( 0.99 L / min) with air, and 100 RPM( 1.32 L / min) with air. 4. Sucker air injection was stopped, and this sequence was repeated at levels of 500 mL and 1000 mL. Data was collected from the Gampt BCC300 continuously throughout the protocol, and markers were applied to denote interventional changes and start / stop times. The first three minutes( 180 s) of bubble data were analyzed for each intervention.
one to two hours of blood collection and completed within four to five hours after blood collection.
GME measurement
A pulsed ultrasonic Doppler system, the Bubble Counter Clinical BCC300( Gampt, Zappendorf, Germany), was used to measure the air generated during each trial. This device counts the number of bubbles passing through the probes each second, measures the diameter, and derives the bubble volume. Bubbles were measured at three locations using 3 / 8-inch clampon probes coated in ultrasonic gel( Figure 1). The first sensor was placed three inches below the exit of the tested reservoir, between the reservoir and the centrifugal pump, and designated as the“ venous” sensor. The second sensor was placed on the arterial outflow( post-oxygenator / filter), twelve inches before the venous inlet on the patient reservoir, and designated as the“ arterial” sensor. The final sensor was placed three inches below the exit of the patient reservoir before the venous inlet of the test reservoir and was designated as the“ recirculation” sensor. Trial data collection and interventions did not begin until all probes were clear of GME.
After each trial, raw data were exported from the BCC300 onto a thumb drive as an MS Excel file. Markers were placed with each intervention, which was also displayed on the spreadsheet. The first three minutes( 180 s) of bubble count data were then formatted and loaded onto a PC for analysis.
Testing conditions
To mitigate confounding variables, testing conditions during all experimental trials were as follows: Arterial blood flow was recirculated at 4.5 L / min, and blood temperature measured at the oxygenator outlet was maintained at 37 ° C. 100 % oxygen was administered into the oxygenator gas in port at 4.5 L / min sweep to match blood flow. The hematocrit was maintained between 23 % and 25 %, and the activated clotting time was maintained above 480 s following heparin administration, which was acceptable to begin the trial [ 38 ]. Air administration into the pump sucker tubing was continuous at 0.20 L / min except during baseline measurements when it was turned off. The variables altered and assessed during the experiment were the test reservoir level and the suction roller pump suction speed.
Protocol
After thoroughly de-airing the blood-primed circuit, the arterial centrifugal pump flow was set at 4.5 L / min, and a 100 % oxygen sweep was matched to the blood flow. The arterial temperature was maintained at 37 ° C. The sequence of interventions and data collection( Figure 2) was identical at each“ test reservoir” level( 200 mL, 500 mL, and 1000 mL). The level was set at the desired value by manipulating a Hoffman clamp on the“ patient reservoir” outlet line. During each intervention, bubble count data from three probes( venous, arterial, and recirculation) were measured simultaneously.
Baseline measurements were made at a sucker speed of 25 RPM( 0.32 L / min) with no air injection into the suckers. The air injection roller pump was then started and increased to 0.20 L / min to introduce room air into the sucker blood returning to the test reservoir. Measurements with aerated sucker return were then obtained at 25 RPM( 0.32 L / min), 50 RPM( 0.65 L / min), 75 RPM( 0.99 L / min), and 100 RPM( 1.32 L / min). The air injection pump was then stopped, the level reset to the desired value, and this sequence was repeated. The bubble count per second was measured continuously by the Gampt BCC300 throughout the protocol, and markers were applied to denote interventional changes and start / stop times.