PUMPING DEVICE FOR OPERATING AN
INTRA-AORTIC BALLOON
FIELD OF THE INVENTION 5
'The present invention pertains to a device for use in conjunction with an intra-aortic balloon pump. More particularly, the present invention concerns a device for driving/operating an intra-aortic balloon pump that has an arterial pressure sensor associated therewith. 10
BACKGROUND OF THE INVENTION
Electrocardiograms or arterial pressure signals have long been helpful in the treatment of patients when used in conjunction with intra-aortic balloon pumps. Japa- 15 nese Patent Publication No. 62-189049 (1987) discloses one example of how arterial pressure signals can be obtained. As described in that publication, an arterial pressure sensor is set in place at the tip of the intra-aortic balloon pump. 20
However, when an arterial pressure sensor is set at the tip of the intra-aortic balloon pump, the intra-aortic balloon pump and the sensor are inserted completely into the patient's body. As a result, it is difficult to keep the pump properly calibrated by appropriately main- 25 taining the zero point of the sensor. Therefore, with conventional devices, the zero point gradually fluctuates, thereby preventing users from accurately detecting arterial pressure. This is a problem that has been noted with conventional devices of the aforementioned 30 typeOther types of intra-aortic balloon pumps are disclosed in U.S. Pat. Nos. 4,692,148; 4,733,652; 4,794,910; 4,796,606; 4,809,681; and 4,832,005.
SUMMARY OF THE PRESENT INVENTION 35
In light of the foregoing discussion, it can be seen that known types of balloon pumps are susceptible to certain improvements. As a result, the present invention was designed to provide a device that makes it possible to 40 adjust the zero point of the arterial pressure sensor after it has been inserted into the aorta and during use.
To achieve the foregoing advantage, the present invention includes an arterial pressure sensor which is set in place at the tip of an intra-aortic balloon pump, a 45 pressure sensor associated with the balloon pump for measuring the internal pressure of the balloon pump, means for applying a positive pressure to supply a gas in a substantially uniform amount to the balloon pump to thereby inflate the balloon pump, and an adjuster for 50 comparing the arterial pressure measured by the artery sensor with the internal pressure of the balloon pump detected by the pressure sensor, and thereafter adjusting the zero point of the arterial pressure sensor so as to eliminate any difference between the arterial pressure 55 and the internal pressure of the balloon pump.
By the present invention, the proper amount of gas is supplied to the balloon pump through the application of pressure, and, consequently, the balloon pump is inflated. During that time, the balloon pump will continue 60 to inflate until the internal pressure of the balloon pump is the same as the arterial pressure. When the internal pressure and the arterial pressure are substantially equal, inflation of the balloon pump ceases. Once the inflation of the balloon pump has stopped, the internal 65 pressure of the balloon pump and the pressure of the artery will be the same. When conditions are at that state, the adjuster will compare the arterial pressure
2
with the internal pressure of the balloon pump, adjust the zero point of the arterial pressure sensor accordingly.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the device according to the present invention for operating/driving a balloon pump having an arterial pressure sensor will become apparent from the description bellows, considered in conjunction with the accompanying drawing figures in which like elements bear like reference numerals and wherein:
FIG. 1 is a block diagram illustrating the general features of the driver for operating the balloon pump;
FIG. 2(a) is a flowchart illustrating the manner of operation of the electronic controller;
FIG. 2(b) is a flowchart illustrating the manner in which the zero point is adjusted;
FIG. 2(c) is a flowchart illustrating the manner of operation of the display panel;
FIG. 3 is a perspective view illustrating a patient being treated with a balloon pump, and including a device according to the present invention for driving the balloon pump;
FIG. 4 is a graph illustrating the relationship between the arterial pressure and the inflation/contraction of the balloon pump; and
FIG. 5 is a graph illustrating the relationship between the pressure measured by the arterial pressure sensor and the pressure measured by the pressure sensor positioned away form the aorta.
DETAILED DESCRIPTION O THE PREFERRED EMBODIMENT
Referring initially to FIG. 3 which depicts a patient 1 lying on a hospital bed 2 and being treated with an intra-aortic balloon pump (hereinafter referred to as a "balloon pump"), as the device 3 for driving the balloon pump 4 (hereinafter referred to as the "driver") is placed near the hospital bed 2. The balloon pump 4 can be introduced into the aorta via the patient's femoral artery. Since there are various methods known in the field for implanting the balloon pump 4 into the body of a patient 1, a discussion of such method is not included herein. However, by way of example, it is to be noted that the seldinger method can be utilized to insert the balloon pump 4 into the body of the patient 1.
Referring to FIG. 1, the features of the driver 3 according to a preferred embodiment of the present invention for operating the balloon pump 4 can be seen. The balloon pump 4 is equipped with a tube 4a that is connected to the driver 3, a balloon 4b that inflates and contacts within the aorata, and an arterial pressure sensor 4c that is located at the tip of the balloon 4b. In addition, the driver 3 includes a positive/negative pressure generator 31 which alternately supplies positive pressure and negative pressure to the balloon pump 4, an electronic controller 32, a blood pressure waveform synchronizing circuit 33, an arterial pressure waveform amplifier 34, a balloon pump pressure sensor 35, and a display panel 36.
In accordance with the preferred embodiment, the arterial pressure sensor 4c generates electrical signals that ar proportional to the magnitude of the arterial pressure inside the aorta. The arterial pressure sensor 4c can be as small as, for example, a particle of rice. The pressure sensor 35 is utilized in the zero point adjustment of the arterial pressure sensor 4c. This pressure
20
sensor 35 is utilized because it is more reliable and more precise than the arterial pressure sensor 4c.
The positive/negative pressure generator 31 is equipped with a positive pressure source 311, a negative pressure source 312, a positive pressure opening/shut- 5 off valve 313, a negative pressure opening/shut-off valve 314, an isolator 315, and a common valve 316. The isolator 315 has a primary chamber 315a, a secondary chamber 315c and a movable diaphragm or membrane 3156 that separates the primary chamber 315a '0 from the secondary chamber 3156. A sufficient amount of fluid is provided in the primary chamber 315a and the secondary chamber 315c to ensure proper operation of the system. In this example, helium gas is used as the gas that is supplied to the balloon pump 4. 15
The positive voltage opening/shut-off valve 313 and the negative pressure opening/shut-off valve 314 are connected to the primary chamber 315a. When the positive pressure opening/shut-off valve 313 is open and the negative pressure opening/shut-off valve 314 is closed, positive pressure will be directed from the positive pressure source 311 into the primary chamber 315a. As a result, the movable membrane 3156 will move toward the secondary chamber 315c. During this period 2J of time, if the common valve 316 is open, the balloon 46 on the balloon pump 4 will inflate.
In contrast, if the negative pressure opening/shut-off valve 314 is open and the positive pressure opening/shut-off valve 313 is closed, negative pressure will be ^ directed from the negative pressure source 312 into the primary chamber 315a. If the common valve 316 is open during such period of time, the movable membrane 3156 will move towards the primary chamber 315a. As a result, the balloon 46 on the balloon pump will con- 35 tract or deflate. The positive pressure opening/shut-off valve 313, the negative pressure opening/shut-off valve 314, and the common valve 316 open and close as a result of the electronic controller that operates in accordance with signals output from the blood pressure 40 waveform synchronizing circuit 33.
The pressure sensor 35 is attached to the tube 4a that connects the common valve 316 and the balloon pump 4 and the pressure sensor 35 detects the internal pressure of the balloon pump 4. The pressure sensor 35 is 45 also connected to the electronic control circuit 32.
The arterial pressure sensor 4c, which is located on the tip of the balloon pump 4, is connected to the amplifier 34. The amplifier 34 amplifies the electrical signals, which have been detected and outputted by the arterial 50 pressure sensor 4c, at the zero point set by the electronic control circuit 32. The signals, which have been amplified, are input into the blood pressure waveform synchronizing circuit 33 and the electronic control circuit 32. The blood pressure synchronizing circuit 33 deter- 55 mines the natural heartbeat from the signals output from the amplifier 34 and the blood pressure synchronizing circuit 33 outputs to the electronic control circuit 32 pulse signals that have been synchronized to the natural heartbeat. Additionally, the electronic control circuit 60 32 displays the arterial pressure on the display panel 36.
Reference is made to the flowchart depicted in FIG. 2(a) which illustrate the manner of operation of the electronic controller 32.
Turning initially to FIG. 2(a), if the power source of 65 the electronic controller 32 is "on", the electronic controller 32 executes the steps starting with Step SO. Initially, the electronic controller 32 initializes each flag
necessary for processing in later stages (Step SI). Next, the timer is started (Step S2).
By referring to the timer, the electronic controller 32 then determines whether it is time to make an adjustment to the zero point (Step S3). If it is determined that the prescribed time interval has passed, the electronic control circuit 32 carries out an adjustment of the zero point (Step 4). Thereafter, the timer is restarted in preparation for the next zero point adjustment (Step S5). If it is determined in (Step S3) that it is not time to make an adjustment, the electronic controller 32 operates the balloon pump 4 used in the treatment of the patient 1, and also displays the arterial pressure of the patient 1 (Step S6).
To explain in general the operation/driving of the balloon pump that is performed in Step S6, reference is made to FIG. 4 which illustrates the relationship between the waveform of the arterial pressure and the inflation/contraction of the balloon pump 4.
The balloon pump 4 will be made to contract a few seconds before the arterial pressure rises, i.e., the heart contraction period. As a result of the contraction of the balloon pump 4, the arterial pressure of the aorta 42 drops, which means that blood can be easily pumped from the chambers of the heart 43. As a result, the blood flow rate increases at that time, and that aids in the recovery of the patient 1. After the peak in the arterial pressure has been observed, the balloon pump 4 is inflated after the prescribed period of time, i.e., at the time of expansion of the heart. As a result of the inflation of the balloon pump 4, the arterial pressure of the main section of the aorta 42 increases. In consequence, there is an increase in the amount of blood flowing to the coronary arteria 44. Thus, there is an added supply of oxygen and nutrients to the hearts, which aids in the recovery of a weakened heart.
As explained herein, at Step S6, the positive pressure opening/shut-off valve 313 and the negative pressure opening/shut-off valve 314 alternately close in response to the beats of the heart that are detected by the blood pressure waveform synchronizer. As a result, the balloon pump 4 inflates and contracts.
Moreover, at Step S6, at the same time as the inflation and contraction of the balloon pump 4, there is a display of the arterial pressure on the display panel 36. The patient 1 can be treated as the physician observes the arterial pressure displayed on the display panel 36.
With reference to FIG. 2(c), an explanation will be provided of how the arterial pressure is displayed on the display panel 36.
First, the initial settings for the registers Pmax, Pmin, and Pas are set (Step S81). The register Pmax records the maximum blood pressure for the natural heart. The register Pmin records the minimum blood pressure for the natural heart. The register Pas records the assist pressure resulting from the balloon pump 4.
At Step S82, a determination is made as to whether the balloon pump 4 is contracting. If the balloon pump 4 is contracting (Yes), the arterial pressure detected by the arterial pressure sensor 4c will be stored in register Pn (Step S83).
Thereafter, the steps necessary for determining the maximum blood pressure (Steps S84, S85, and S88) and the steps necessary for determining the minimum blood pressure (Steps S86, S87, and S88) for a natural heart are carried through. The maximum blood pressure and the minimum blood pressure are then displayed.
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