Table 2 Mean difference in signal intensity (measured in decibels) at the four pump head speeds and two infusion rates in circuits with and without an oxygenator

1000 rpm oxygenator 150 ml/h

4.2 ± 2.6

1000 rpm no oxygenator 150 ml/h

1.4 ± 1.3

p < 0.0001

2000 rpm oxygenator 150 ml/h

4.5 ± 2.1

2000 rpm no oxygenator 150 ml/h

0.6 ± 1.6

p < 0.0001

3000 rpm oxygenator 150 ml/h

7.1 ± 2.4

3000 rpm no oxygenator 150 ml/h

0.7 ± 1.0

p < 0.0001

4000 rpm oxygenator 150 ml/h

6.7 ± 2.5

4000 rpm no oxygenator 150 ml/h

2.5 ± 1.0

p < 0.0001

1000 rpm oxygenator 300 ml/h

5.9 ± 2.7

1000 rpm no oxygenator 300 ml/h

0.6 ± 2.3

p < 0.0001

2000 rpm oxygenator 300 ml/h

3.9 ± 2.0

2000 rpm no oxygenator 300 ml/h

2.5 ± 1.6

p < 0.0001

3000 rpm oxygenator 300 ml/h

4.6 ± 1.4

3000 rpm no oxygenator 300 ml/h

1.6 ± 1.1

p < 0.0001

4000 rpm oxygenator 300 ml/h

6.1 ± 1.5

4000 rpm no oxygenator 300 ml/h

2.9 ± 0.7

p < 0.0001