A S m a l l Pulsatile P u m p f o r Extracorporeal Circulation Yoshitaka SASAKI, Hidefumi SAKABE, Tomotsugu HARA and Isamu HASHIMOTO A B S T R A C T : A new pulsatile pump was constructed with variable beat rate and the stroke volume, controlled systolic maximum pressure and a very steep built-up curve, to be used for extracorporeal circulation. KEY W O R D S : Extracorporeal circulation, pulsatile pump, cam, coil spring, Bellofram rolling diaphragm, free length, set length.

INTRODUCTION A t the present time extracorporeal circulation is mostly done with non-pulsatile pumps. However, since the physiological circulation is naturally pulsatile, extracorporeal circulation should also be pulsatile, thus making it more compatible with natural physical conditions. 1~11 Since no suitable pulsatile pump is available at present to study extracorporeal circulation in small animals, we designed and constructed a new pump, with which it is possible to change both the stroke volume and the beat rate. One important aspect of this machine is that it is driven by a coil spring. Its highest pressure is set by the spring so that possible rupture of the blood vessels is minimized because the blood pressure can not exceed the pressure exerted by the spring.

MATERIALS AND METHOD The machine consisted of two main parts, the blood chamber and its driving part as shown in Figs. 1 and 2. One end of the blood chamber consisted of a Bellofram rolling diaphragm with two valves built into the housing. The driving part consisted of an electric motor, a specially designed cam, a steel coil spring and a connecting rod.

Blood Chamber A cross section of the blood chamber is shown in Fig. 3. One end of the blood chamber consisted of a Bellofram rolling diaphragm connected to the driving part by a connecting rod. Inlet and outlet valves were built into the chamber. These were hinged leaflet polyurethane valves fixed at an angle of 45 ~ against the flow axis.

Electric Motor A commercial electric motor was used for rotating the cam. Its revolutions were slowed down by gears. The revolution rate of the cam could be varied from 0 to about 100 r.p.m.

Cam The cam had two-fold purpose : to change the stroke volume, and to achieve the rapid release of the spring. In order for the distance from the central axis to the cam surface to increase gradually during diastole, and to obtain rapid decrease during systole, the distance in one cross sectional plane during cam rotation was plotted as shown in Fig. 4. To vary the stroke, the cam projection was inclined obliquely from the top to the bottom surface. Thus the shape of the cam was designed as shown in Fig. 5.

From the Department of Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan JAPANESEJOURNALOF SUROEgY,Vol. 7, No. 2, pp. 90-95, 1977

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Motor ] ~ ~ ~ ~ B e l lroonilgf diraaphragm m 0 Cam / /

/Adjust ...... f / sottiog~engtb ~

/

/

Spring

Bloodchamber

C. . . . ctingrod

I

Fig. 1.

Pulsatile pump (diagram).

Fig. 2.

Pulsatile pump.

Spring The spring was the main source of the force in this machine and controlled the blood pressure. It was a steel coil spring and set into the machine with some degree of compression. The force of the spring could be changed by three methods. The one was to change the free length of the spring. I f a longer spring was set in the same set length, spring compression was greater than with the shorter one, a n d exerted a stronger force. The other was

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Fig. 3.

Jap. J. Surg. June 1977

Blood c h a m b e r .

distance

z Fig. 4.

1.5 ~r

0

0.5 z

z

angle

Distance from the central axis to the c a m surface d u r i n g c a m rotation.

Fig. 5.

Cam.

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to change the set length. I f the set length was shortened, the spring was more tightly compressed resulting in a stronger force. T h e third was to change the d i a m e t e r of the steel wire of which the spring was constructed, i.e. the larger the spring wire the greater the force was.

Connecting Rod T h e c o n n e c t i n g rod was a steel b a r with a square shaped frame, which t r a n s m i t t e d the force from the spring to the Bellofram rolling d i a p h r a g m .

Working Mechanism D u r i n g diastole the c a m rotated g r a d u a l l y increasing the distance from the central axis of the c a m to the c a m surface, thus slowly compressing the spring a n d d r a w i n g the

\ mmHg

0

Fig. 6.

Fig. 7.

1 sec. Pressure curve in the blood chamber.

The method of measurement of output; Water in the dish is drained to the pump with 15 cm. of water head. The water from the pump is ejected to 60 era. above. A T-shaped cannula is fixed at the top of the tube. From these openings water is ejected into a cylinder 136 cm. deep giving a load of 100 mmHg. to the cannula. The flow was measured by a graduated cylinder.

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connecting rod and the Bellofram back. The inlet valve of the blood chamber opens, the outlet valve closes, and blood flows into the blood chamber. During systole the cam rotated farther than in the diastolic phase. The distance from the central axis of the cam to the cam surface abruptly decreased. This sudden decrease released spring compression driving the rod and Bellofram back into the housing. The inlet valve of the blood chamber closes, the outlet valve opens, and blood is ejected. Control Mechanism The highest pressure in the blood chamber could be changed by changing the free length of the spring, the set length of the spring, and the diameter of the wire, of which the spring was constructed. The output could be controlled by both the stroke volume and b.p.m. (beats per minute). The stroke volume could be varied by changing the stroke of the

output ml/min

i000 stroke

mta

15.0 12.5 10.0

500-

7.5 5.0

5'0 beats

100 beats/min

Fig. 8. Beat-output curve.

stroke volume ml/beat I0

:

stroke

ram

15.0 12.5 10.0

5 "~'--: :

:

"

~ ~

7.5 ~

5'0

"

~

~'*"~

5.0

160 beats/rain beats

Fig. 9.

Beat-stroke volume curve.

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Bellofram rolling d i a p h r a g m w i t h the same sectional area. This could be d o n e b y sliding the c a m along the central axis. T h e b . p . m , could be c h a n g e d from 0 to a b o u t 100 b . p . m . RESULTS T h e b l o o d pressure curve in the b l o o d c h a m b e r of the m a c h i n e was o b t a i n e d using a r a b b i t b y m e a s u r i n g the pressure w i t h a t r a n s d u c e r (Fig. 6). T h e c h a n g e in o u t p u t of the p u m p with v a r i e d b . p . m , a n d the stroke was m e a s u r e d as shown in Fig. 7. T h e b e a t - o u t p u t curves a n d the beat-stroke v o l u m e curves a r e shown in Figs. 8 a n d 9. DISCUSSION T h e pressure curve in the b l o o d c h a m b e r shown in Fig. 6 closely resembles the n a t u r a l h e a r t pressure curve, a n d its pressure b u i l t - u p is steep. T h e o u t p u t increases a c c o r d i n g to the increase of b . p . m , w i t h the same stroke as shown in Fig. 8. H o w e v e r , at relatively high b.p.m., the degree o f increase in o u t p u t p e r the degree of increase in b . p . m , becomes smaller, w h i c h is p r o b a b l y d u e to the decrease in the net stroke v o l u m e at high b . p . m , as shown clearly in Fig. 9. T h e relationship b e t w e e n b.p.m, a n d stroke v o l u m e is shown in Fig. 9. Stroke v o l u m e tends to decrease with the increase o f the b.p.m, at the same stroke. T h e d e g r e e o f decrease in stroke v o l u m e is g r e a t e r a t a g r e a t e r set stroke t h a n at a s m a l l e r one. H o w e v e r the a c t u a l b e a t - o u t p u t a n d beat-stroke v o l u m e curves o b t a i n a b l e m a y v a r y a c c o r d i n g to the d r i v i n g conditions a n d construction o f the m a c h i n e such as the p o w e r of the spring, the valves built into the b l o o d c h a m b e r , the resistance of the circuit, h e a d from the p u m p to the fluid source a n d l o a d o f the ejected site. (Received for publication on December 9, 1976) References 1. Giron, F., BirtweU, W.C., Soroff, H.S. and Deterling, R.A.: Hemodynamic effect of pulsatile and nonpulsatile flow, Arch. Surg. 93: 802-810, 1966. 2. Kubo, K., Kusakawa, M. and Yada, K.: The physiological role of pulsatile flow during extra corporeal circulation, Kyobu Geka (Jpn. J. Thorac. Surg.) 20: 385-393, 1972 (in Japanese). 3. Kusakawa, M., Yada, K. and Kubo, K.: The effect of venous pulse during extra corporeal circulation, Shinzo (Heart) 5: 702-705, 1973 (in Japanese). 4. Kusakawa, M., Yamazaki, Y. and Kubo, K. : Post perfusion lung syndrome and pulsatile perfusion, Shinzo (Heart) 6: 904-906, 1974 (in Japanese). 5. Mandelbaum, I. and Burns, W.H.: Pulsatile and nonpulsatile blood flow, J.A.M.A. 191 : 121-124, 1965. 6. Takahashi, H., Washizu, T., Sakakibara, K., Konishi, S., Aoki, R., Wakai, S. and Yamada, T.: Air driven pulsatile blood pump and minituarization of heart lung machine, Shinzo (Heart) 4: 258-260, 1972 (in Japanese).

7. Takigawa, K.: The role of pulsatile flow during extra corporeal circulation, especially about renal circulation Nippon Kyobu Geka Gakkai Zasshi (J. Jpn. Assoc. Thorac. Surg.) 19: 526-542, 1971 (in Japanese). 8. Tomino, T., Yokosuka, T., Kitamura, N., Kawafuku, K., Yanagisawa, M., Konno, S., Umezu, M. and Tsuchiya, K.: The construction of an artificial heart which the atrium and ventricle are driven, and its application for extracorporeal circulation, Jinko Zoki (Artificial Organs) 3 (Suppl.): 106-107, 1974 (in Japanese). 9. Wesolowski, S.A., Sanvage, L.R. and Fine, R.D. : The role of the pulse in maintenance of the systemic circulation during heart-lung bypass, Surgery 37: 663-682, 1955. 10. 'Wilkens, H., Regelson, W. and Hoffmeister, F.S.: The physiologic importance of pulsatile blood flow, N. Engl. J. Med. 267: 443-446, 1962. 11. Yamazaki, Z., Fujimori, Y., Ogawa, Y., Togawa, T. and Kamiya, R. : Physiological effect of pulsatile flow, from the aspect of renal and lymph flow, Shinzo (Heart) 4: 255-257, 1972 (in Japanese).

A small pulsatile pump for extracorporeal circulation.

A S m a l l Pulsatile P u m p f o r Extracorporeal Circulation Yoshitaka SASAKI, Hidefumi SAKABE, Tomotsugu HARA and Isamu HASHIMOTO A B S T R A C T :...
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