Defining Elements of Roller Pump Occlusion in Cardiopulmonary

Bypass Surgery

SHOTA KATO1,2, SHOTA SOGABE1, JUN YOSHIOKA3, KAZUHIKO NAKADATE4,

HITOSHI KIJIMA1, YASUTOMO NOMURA2

1Department of Medical Technology and Clinical Engineering,

Gunma University of Health and Welfare,

191-1 Kawamagarimachi Maebashi Gunma 371-0823,

JAPAN

2Maebashi Institute of Technology Graduate School of Environment and Biotechnology,

460-1, Kamisadori Maebashi Gunma 371-0816,

JAPAN

3Sendai Red Cross Hospital Medical Technology Department,

Clinical Engineering Technology Division,

2-43-3, Hakugiyamahonchou Sendai Miyagi 982-8501,

JAPAN

4Department of Basic Science Educational and Research Center for Pharmacy,

Meiji Pharmaceutical University,

2-522-1Nojiri Kiyose Tokyo 204-8588,

JAPAN

Abstract: - In surgery, centrifugal pumps are used when safety and biocompatibility are priorities. On the other

hand, when considering operability and economy, roller pumps are used. The roller pump occlusion has to pay

attention to the long-time operation causing axis displacement; Our study carried out that perfusion temperature

executed the technology as a rule factor of the occlusion. To evaluate the manifestation of the circumference of

the occlusion, we used three kinds of different roller diameters and measured perfusion temperature (Pt) and the

electrical resistivity (Er), a pressure degree of the occlusion. Based on Japan Industrial Standard -T1603, we

observed the differences between the three pumps with degree of the occlusion which we were setting in the

same condition as a change of the occlusion by the progress at a time. Pt and Er repeated the up-down motion

in three pumps every 30-60 minutes. In addition, the occlusion extended the interval in progress at a time. The

pressure level of the sensor rose every 30 minutes and became unmeasurable afterward. This phenomenon

affects that perfusion temperature changes influence the blood viscosity and, we suppose that it influenced a

rise in para-blood temperature and it appeared in pressure change and Er of the occlusion. Therefore, control of

the Pt leads to the appropriate control of the roller pump and we will be able to carry out physiological

extracorporeal considering an indispensable element as SDGs.

Key-Words: - Occlusion, Perfusion Temperature (Pt), Electrical Resistivity (Er), Circumferential runout,

Pressure sensor, Blood cell destruction, Mechanical fracture.

Received: August 3, 2023. Revised: December 22, 2023. Accepted: January 28, 2024. Published: Arpil 1, 2024.

1 Introduction

As a characteristic of centrifugal pumps, the

perfusion amount may change due to low head and

changes in afterload, [1]. There are also reports that

there is no significant difference in blood damage

when comparing centrifugal pumps and roller

pumps used in heart-lung surgery, [2], [3].

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Roller pumps are easy to operate, but the drawback

is that the occlusion cannot be adjusted during

surgery. Furthermore, there is a concern that red

blood cells may be destroyed due to changes in the

occlusion. In the world of blood rheology, it is said

that a decrease in the negative charge (zeta

potential) contained in sialic acid in the red blood

cell membrane and changes in the morphology of

the outer membrane wall increase the aggregation of

blood cells, [4], [5], [6]. Therefore, as a previous

study, a method has been reported in which the

occlusion of a roller pump is converted into an

electrical resistance value (Er: Electrical Resistance)

and then quantified intermittently, [7].

In this study, we focused on the behaviors of Er

due to temperature changes (Pt : Perfusion

Temperature) to continuously monitor changes in

the occlusion during roller pump operation using

simulated blood.

2 Materials and Methods

2.1 Experimental Equipment

Three types of pumps with different roller diameters

are available : Terumo CV-8000 (roller diameter 42

mm), Technowood BP-150 (roller diameter 22 mm),

and Livanova S5 (roller diameter 31 mm). used in the

experiment (Figure 1).

Fig. 1: Experimental used three roller parts

diameters

For the blood circuit, a roller pump was set with a

Mera Excel line H 3/8 inch tube (MERA Corp.,

Tokyo, Japan), inner diameter 9.5 mm, outer

diameter 14.3 mm, Shore hardness A70 degrees, and

tensile strength 13.4 MPa. The experimental

environment temperature was set to 25 (±2) °C, and

simulated blood mixed with glycerin and

physiological saline (0.9% wt) and 40% glycerin

aqueous solution (4.18 cP) were mixed with human

blood at 25 °C (37 °C). The same viscosity) was

prepared, [8], [9].

2. 2 How to Measure Controlling Factors

In addition, to confirm the change in perfusion

amount when the solution was circulated through the

tube, the pressure closure degree of CV-8000,

BP-150, and S5 was set to 6 drops/min and 13

drops/min, and the maximum average value of five

flow rate displays (ultrasonic flow meter and

tachometer) was evaluated. When we compared the

perfusion rates between the ultrasonic flowmeter and

the tachometer, we found that the difference between

the occlusion rate of 13 drops/min was smaller than

the occlusion rate of 6 drops/min, so we decided to

use the occlusion rate of 13 drops/min as the standard.

The experiment was conducted (Table 1).

The experimental outline was as follows

JIS-T1603: the occlusion of each pump was set to 13

drops/min, the perfusion fluid volume was 500 mL,

the rotation speed was 97 rpm, the perfusion time

was 180 minutes, and the pumps were moved every

30 minutes to an arbitrary point A (Figure 2), and the

electrical resistance value Er and perfusion

temperature Pt were sequentially measured under the

same conditions, [10].

Table. 1 Volumetric flow rate of rotary flowmeter (R)

and ultrasonic flowmeter (U) with occlusion

of 6 drops and 13 drops

6 drops/min 97 rpm 25℃

Time[min]

CV-8000

2480

2484

2488

2492

2718

2756

2796

2800

2804

-150

2580

2634

2662

2654

2652

2520

2548

2564

2582

6 drops/min 97 rpm 25℃

Time[min]

CV-8000

2480

2484

2488

2492

2496

2694

2704

2738

2742

-150

2580

2578

2562

2576

2566

2592

2520

2506

2494

2534

2532

2558

：

Volumetric flow rate of rotary flowmeter

：

Ultrasonic flowmeter

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Fig. 2: Electrical resistivity measurement circuit

2.3 Pressure Measurement using a Pressure

Sensor

A small pressure sensor PS-70KC M2: 7 MPa

(Kyowa Dengyo Co. Ltd, Tokyo, Japan) was fixed

to the area where the roller and raceway were

crimped (Figure 3), and pressure changes were

observed. WGI-400A-00 (Kyowa Dengyo Co. Ltd,

Tokyo, Japan) was used as the measuring instrument,

and measurements were made under the conditions

of a sampling frequency of 50 Hz, a bridge power

supply of DC2 V, 30 mA, and an output voltage of

10 V. In addition, the pressure value of the degree of

closure was measured every 30 minutes.

Fig. 3: Schema of pressure measurement sensor

install site for occlusion pressure

3 Results

3. 1 Changes in the occlusion due to Er and

(1) CV-8000

Figure 4 shows the average values of Er and Pt from

the start of CV-8000 perfusion to 180 min.

Furthermore, Er converged to 40 to 46 kΩ for a

roller with a diameter of 42 mm.

Er decreased by 0.5 kΩ 30 min after the start,

and after that, it repeated up and down movements.

On the other hand, Pt showed a waveform with an

opposite tendency. The correlation coefficient of

regression analysis of Er and Pt was R2 =0.74

(p<0.05), which showed a strong correlation.

Fig. 4: Serial changes in Er and pt with CV-8000

(2) BP-150

Figure 5 shows the results for Er and Pt. The Er of

BP-150 converged to 37 to 44 kΩ.

From Figure 5, Er decreased by 0.6 kΩ 30 min

after the start, and then repeatedly fluctuated up and

down. Pt showed a waveform with an opposite trend.

The correlation coefficient of regression analysis of

Er and Pt showed a significant correlation of R2

=0.61 (p<0.05).

Fig. 5: Serial changes in Er and pt with BP-150

(3) S5

The results for Er and Pt are shown in Figure 6. The

Er of S5 converged to 29 to 34 kΩ.

From Figure 6, Er decreased by 1 kΩ 30 min

after the start, and then gradually decreased. The

waveform increased 150 minutes after the start but

decreased overall. On the contrary, Pt showed a

waveform with a tendency opposite to that of Er.

The correlation coefficient of regression analysis of

Er and Pt showed a significant correlation with

R2=0.66 (p<0.05).

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Fig. 6: Serial changes in Er and pt with S5

3.2 Changes in Pressure due to Changes in

the Occlusion

Before the start of the experiment, the B-150's roller

pump was set at a drop rate of 13 drops/min, and the

pressure value for the occlusion was 6 MPa, but it

increased to 7 MPa 30 minutes after the start, and 8

MPa after 60 minutes, pressure beyond the

measurement range was applied, making

measurement impossible.

4 Discussion

4.1 Degree of Occlusion Predicted from Pt

As a result of examining the correlation between Er

and Pt using pumps with different roller diameters,

the Er of the CV-8000 and BP-150 pumps converged

within the optimal occlusion, and S5 converged

around 30 to 34 kΩ. In S5, the value is lower than the

optimum occlusion, and it is necessary to mention the

internal structure of the pump related to pressure

closure.

However, in all pumps, a negative correlation

(inverse proportion) between Er and Pt was observed,

and a phenomenon in which the occlusion (electrical

resistance value) decreased as the perfusion

temperature Pt increased was observed. Especially in

BP-150, when the deviation of Pt is large, the

deviation of Er also becomes large. This is thought to

be due to the frictional heat caused by the roller

rubbing against the tube as Pt increases, which

activates the molecular motion of the perfused

substance, making the density sparse and reducing

the electrical resistance value Er. It is thought that the

increase in Pt lowers the viscosity of the substance,

indicating a state in which the electrical resistance

decreases, and decreases Er.

In the case of continuous perfusion, frictional

heat is accumulated when the roller contacts the tube,

but since the perfusion temperature Pt is below 50°C,

changes in the tube due to the viscosity of the

perfusate were ignored, [11].

4.2 Relationship between Changes in

Occlusion and Pressure Sensor

The pressure measuring device used in this study

only displayed discrete instantaneous values and did

not record waveforms, making it impossible to

perform a detailed analysis of pressure sensor

damage.

However, it is believed that the cause of the

sensor damage was that the drive shaft supporting the

rollers caused circumferential vibration, causing the

rollers to approach the raceway and apply high

pressure to the pressure sensor PS-70KC M2.

In addition, the pressure applied to the strain

gauge is considered to be ➀ vertical pressure and

pressure (shear stress) applied to the curved raceway

due to the rotation of the rollers ➁ acting on the

pressure sensor (Figure 7).

Fig. 7: Pressure to depended on a sensor and

Transformation of the tube

The pressure can be expressed by the following

equation, where N is the force with which the roller

pushes out the tube, ➀ is the pressure N0 that pushes

out the tube in an unpressurized state, and ➁ is the

fluid force acting on the roller, [12], (Figure 7)

N = N0 +   





= 

 {(2r - 2w – R)  sinθ + R}

: Tube internal pressure

: Tube thickness

: Radius of roller r: Outside radius of tube cross

section



: Maximum contact angle between roller and

tube



: Width of the tube at any point in contact with

the roller

Based on the pressure measurement and

calculation formula of the roller pump, it is predicted

that the high pressure caused by circumferential

vibration will cause a major disturbance to the actual

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blood because it will increase the perfusion

temperature Pt.

4.3 Blood Cell Destruction Expected due to

Circumferential Vibration

When using a roller pump in a clinical setting, it is

necessary to pay attention to the fact that the

frictional heat generated by rubbing the tube changes

the plasma viscosity of the blood and changes the

internal structure of red blood cells, [13]. Red blood

cells are maintained at a constant distance by the

electrical repulsion of the zeta potential on the

membrane surface, [14]. However, the reduction in

the amount of sialic acid and the loss of protein is

thought to increase the rate of red blood cell

aggregate formation and reduce the repulsive force

between blood cells, thereby increasing blood

aggregation, [15], [16]. Therefore, the frictional heat

and pressure changes generated by the rotating

rollers can be expected to disrupt the red blood cell

membrane.

Therefore, the narrowing of the interval between

the occlusion due to circumferential vibration leads

to the collapse of blood cells, resulting in changes in

plasma viscosity due to heat, mechanical collapse,

and changes in blood viscosity due to mechanical

destruction. Blood cell destruction significantly

reduces biological homeostasis, so the occlusion of

the roller pump must be adjusted from time to time.

4.4 As a Quantitative Monitor of the

Occlusion

The need for quantitative monitoring of changes in

the occlusion is an important issue in blood injury.

JIS-B0621 sets standards for circumferential runout,

but the occlusion changes from the time of setting.

Therefore, continuous monitoring is necessary to

ensure proper blood delivery, and it is desirable to

adjust from time to time, [17].

As an indirect method for measuring the

occlusion, it is necessary to monitor the electrical

resistance value Er and simultaneously monitor the

perfusion temperature Pt. Since Er changes

depending on the viscosity of the perfused substance,

it is important to quantify the occlusion because

temperature, electrical resistance, and viscosity are

factors that interfere with each other due to the

temperature rise caused by circumferential vibration.

becomes.

However, when using Er in a clinical setting, it is

not practical because the current is higher than the

minimum sensing current of the human body.

Therefore, by installing thermometers before and

after the roller and continuously monitoring changes

in Pt, it becomes possible to continuously monitor the

degree of pressure closure. As a control factor for the

degree of pressure occlusion, perfusion temperature

Pt is a useful monitoring item and is essential.

5 Conclusion

In surgery, roller pumps are used when considering

operability and economy. The roller pump occlusion

has to pay attention to the long-time operation

causing axis displacement.

(1) Our study carried out that perfusion temperature

executed the technology as a rule factor of the

occlusion.

(2) To evaluate the manifestation of the

circumference of the occlusion, we used three kinds

of different roller diameters and measured perfusion

temperature (Pt) and the electrical resistivity (Er), a

pressure degree of the occlusion.

(3) Control the degree of pressure closure of roller

pumps used in heart-lung machines, it was

understood that the

degree of pressure closure changes due to many

factors, such as circumferential runout and

temperature changes.

(4) This study concludes that the degree of pressure

occlusion changes and that relative monitoring of

perfusion temperature is necessary.

(5) More detailed analysis and experiments are

required, but since each console is expensive, we

plan to confirm this in the future.

(6) Furthermore, we plan to compare not only the

roller pump but also the centrifugal pump in terms of

volumetric flow rate and blood cell morphology.

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Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

- Shota Kato conducted all of the experiments and

wrote the submitted paper.

- Shota Sogabe conducted an experiment on the

volumetric flow rate of ultrasound.

- Jun Yoshioka created a blood cell preservation

solution.

- Kazuhiko Nakadate provided mathematical advice.

- Hitoshi Kijima gave some electric advice.

- Yasutomo Nomura provided mathematical analysis

and advice throughout the experiments.

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

No funding was received for this study.

Conflict of Interest

The authors declare no conflicts of interest relevant

to the content of this article.

Creative Commons Attribution License 4.0

(Attribution 4.0 International, CC BY 4.0)

This article is published under the terms of the

Creative Commons Attribution License 4.0

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