Device and method for measuring volumetric blood flow in a vessel

Device for measuring volumetric blood flow in a vessel comprising a catheter having proximal and distal extremities. A balloon is carried by the distal extremity of the catheter. A balloon inflation lumen is carried by the catheter and is in communication with the balloon. A toroidal ultrasonic transducer is carried by the catheter and is spaced proximally of the balloon. Electrical circuitry is provided for supplying electrical energy to the transducer. The transducer produces a large substantially uniform beam of ultrasonic energy to illuminate a vessel of approximately three centimeters in diameter with the ultrasonic energy.

This invention relates to a device and method for measuring volumetric 
blood flow in a vessel and more particularly to such a device and method 
which utilizes ultrasonics. 
Diagnostic catheters have previously been provided for measuring cardiac 
output and pressures utilizing either thermodilution, dye dilution or 
oxygen consumption methods. More recently intravascular catheters have 
been developed which measure instantaneous flow velocity utilizing doppler 
ultrasonic transducers to measure the "doppler shift" created by the 
movement of red blood cells within the blood vessel of interest. 
Typically, the doppler catheter utilized in such systems have been capable 
of measuring blood flow velocity within a small sample volume contained 
within the blood vessel. Volumetric flow could not be accurately 
determined utilizing such doppler systems because additional information 
such as vessel dimension, flow profile and incidence angle between the 
ultrasonic beam and the direction of flow must be ascertained in order to 
accurately determine volumetric flow. In co-pending application Ser. No. 
036,796 filed on Apr. 10, 1987, pending, there is disclosed an apparatus, 
system and method for measuring volumetric flow of blood in a vessel which 
discloses a catheter and guide wire transducer apparatus and system which 
can be utilized in a method for measuring volumetric blood flow in small 
blood vessels. Typically this is accomplished by the creation of a large 
uniform beam in the far field of a relatively small transducer. However, 
it has been found that there is a need for illuminating vessels of larger 
diameters which cannot be readily accomplished with the apparatus of Ser. 
No. 036,796. There is therefore a need for a new and improved device and 
method for measuring volumetric blood flow in a vessel. More specifically 
there is a need for measuring cardiac output in man by illuminating the 
main pulmonary artery which receives the total blood flow of the heart. 
In general, it is an object of the invention to provide a device and method 
for measuring volumetric blood flow in a vessel in which a large uniform 
beam is created. 
Another object of the invention is to provide a device and method of the 
above character in which it is unnecessary to angularly position the 
transducer. 
Another object of the invention is to provide a device and method of the 
above character capable of measuring volumetric blood flow in a vessel 
independent of position of the transducer within the vessel. 
Another object of the invention is to provide a device and method of the 
above character which can be positioned without the use of fluoroscopy by 
means of a flotation balloon. 
Another object of the invention is to provide a device and method of the 
above character in which independent pulmonary wedge pressure measurements 
can be made simultaneously with cardiac output measurements.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In general, the device for measuring volumetric blood flow in a vessel is 
comprised of an elongate catheter having proximal and distal extremities 
with an inflatable balloon carried by the distal extremity of the same. A 
toroidal transducer is carried by the catheter spaced from the distal 
extremity and is of a size and configuration which creates a large uniform 
beam. In order to achieve the large uniform beam, the transducer itself 
can have a convex configuration in a direction facing the distal extremity 
of the catheter or, alternatively, the transducer can be provided with a 
convex lens serving to spread the beam to create the large uniform field. 
In an alternative embodiment, the catheter can be comprised of first and 
second coaxial catheter members, with the first member carrying the 
ultrasonic transducer and the second member carrying the inflatable 
balloon. 
More specifically as shown in FIGS. 1-5, the device for measuring 
volumetric blood flow in a vessel consists of an elongate catheter 11 
having proximal and distal extremities 12 and 13. The catheter 11 can have 
a suitable length as, for example, 100 centimeters. The catheter is formed 
of a flexible elongate member 14 of a suitable material such as plastic 
which is provided with a portion 14a which is approximately 85 centimeters 
in length and a portion 14b which is approximately 15 centimeters in 
length. The flexible elongate member 14 can be formed in a suitable manner 
such as by extrusion. The portion 14a is provided with five lumens 
extending therethrough whereas a portion 14b is provided with two lumens 
extending therethrough. An inflatable balloon 16 is provided adjacent the 
distal extremity of the catheter 11 and can be formed integral with the 
flexible elongate member 14 or as is well known to those skilled in the 
art can be formed separately on the distal extremity of the catheter. The 
proximal portion 14a of the flexible elongate member 14 can have a 
suitable diameter as, for example, 0.098 inches whereas the portion 14b 
can also be of a suitable diameter as, for example, 0.060 inches. 
With respect to the lumens hereinbefore described, a distal lumen 17 is 
provided having a diameter of approximately 0.020 inches which extends 
from the proximal extremity 12 to the distal extremity of the catheter and 
exits through the distal extremity 14b of the catheter. There is also 
provided a balloon inflation lumen 18 which also extends from the proximal 
extremity to the distal extremity of the catheter. The distal extremity is 
in communication with the interior of the balloon 16 to permit inflation 
and deflation of the balloon. 
A toroidal transducer 21 is carried by the flexible elongate member 14 
adjacent the distal extremity of the portion 14a. A wire lumen 22 is 
provided in the portion 14a for receiving the electrical conducting wires 
24 connected to the transducer 21. The portion 14a of the flexible 
elongate member 14 is provided with a pulmonary artery lumen 26 which is 
in communication with a port 27 provided a suitable distance, as for 
example, adjacent the distal extremity of the portion 14a and spaced 
approximately 14 centimeters from the tip of the distal extremity of the 
catheter 11. The portion 14a is also provided with a right ventricular 
lumen 28 which is in communication with a right ventricular port 29 
opening through the side of the portion 14a as shown particularly in FIG. 
1. The right ventricular port 29 is located approximately 5 centimeters 
proximal of the pulmonary artery port 27 on the catheter 11. The wire 
lumen 22 can have a suitable diameter such as 0.012 inches whereas the 
pulmonary artery lumen and the right ventricular lumen 26 and 28 can have 
similar dimensions such as 0.018 inches. The proximal extremity of the 
catheter 11 is provided with a fitting 31 which includes five extension 
members 32, 33, 34, 36 and 37. Extension members 32, 33, 34, and 36 are 
provided with suitable fittings 38, as for example, Luer-type fittings on 
their proximal extremities. Extension 37 is provided with an electrical 
connector 39 which is connected to conducting wires 24. The distal 
extremities of the tubular extensions 32, 33, 34, 36 and 37 are mounted in 
a fitting 31 so that they are in communication with the five lumens 
provided in the portion 14a of the flexible elongate member 14. Thus by 
way of example, the extension 32 can be in communication with the lumen 
17, extension 33 in communication with the lumen 18, extension 37 in 
communication with the lumen 22 and the extensions 34 and 36 in 
communication with the lumens 26 and 28 respectively. 
As shown in FIG. 1, the transducer 21 is mounted at the transition between 
the portion 14a and 14b of the flexible elongate member 14. As shown 
particularly in FIG. 4, the transducer 21 is formed as a toroid and has a 
convex frontal surface 41 which faces in a direction axially of the 
flexible elongate member 14 and towards the distal extremity of the 
catheter 11. The transducer 21 is coated with a polyurethane coating 42 
and is backed by and secured to the distal extremity of the portion 14a by 
an epoxy-microsphere backing material 43. The transducer 21 is of a size 
and configuration which enables it to create a large uniform beam capable 
of encompassing a vessel at least approximately 3 centimeters in diameter. 
The transducer 21 is coupled by the wires 24 extending through the wire 
lumen 22 to circuitry of the type disclosed in co-pending application Ser. 
No. 036,796 filed on Apr. 10, 1987. 
An alternative embodiment of the invention is shown in FIGS. 5 and 6 in 
which a transducer 51 is provided in the same location as the toroidal 
transducer 21 but which, rather than being convex in shape, is disc-shaped 
having a planar forwardly facing surface 53. The transducer 51 is secured 
to and backed up by an epoxy-microsphere backing material 52. 
In order to obtain a large uniform beam from the transducer 51 which will 
encompass a vessel of at least approximately 3 centimeters in diameter, a 
lens 54 of suitable material such as plastic is mounted upon the surface 
53 of the transducer 51. The lens 54 as shown in FIG. 5 is provided with a 
convex surface 56 which faces forwardly of the catheter toward the distal 
extremity of the same. The lens 54 will cause the focused beam supplied by 
the transducer 51 to spread radially enabling the transducer 51 to create 
a large uniform field for flow measurement in large vessels, as for 
example, 3 centimeters in diameter. In the present embodiment of the 
invention, the transducer 21 is in a fixed location at a point 
approximately 14 centimeters proximal to the distal tip of the catheter 11 
and thus there is a fixed relationship distance with respect to the 
balloon 16 and the transducer 21. 
Still another embodiment of the device and method for measuring volumetric 
blood flow in a vessel is shown in FIGS. 7-10 in which there is shown a 
pulmonary artery catheter assembly 61 which consists of two coaxial 
catheters 62 and 63 in which the inner catheter 62 is slidably mounted in 
the otter catheter 63 for movement axially of the catheter assembly 61. 
The inner catheter 62 consists of a flexible elongate member 66 formed of 
a suitable material such as an extruded plastic which is provided with 
proximal and distal extremities 67 and 68 respectively. A latex balloon 71 
is carried by the distal extremity 68 and preferably is formed of a 
separate balloon which is bonded to the distal extremity in a suitable 
manner such as by an adhesive. The flexible elongate member 66 is provided 
with lumens 72 and 73 extending substantially the entire length thereof in 
which lumen 72 can be identified as the balloon inflation and deflation 
lumen and which is in communication with the interior of the balloon 71. 
The other lumen 73 can be identified as the distal lumen and has the size 
of approximately 0.020 inches and lumen 72 has a size of approximately 
0.008 inches. The exterior of the flexible elongate member 66 can have a 
suitable exterior dimension such as 0.060 inches. The distal lumen 73 
extends through the length of the flexible elongate member 66 and is open 
at the distal extremity to facilitate the making of pressure measurements. 
The outer catheter 63 consists of a flexible elongate member 86 formed with 
a suitable material such as plastic and has a suitable exterior diameter 
such as 0.098 inches. The flexible elongate member 86 has proximal and 
distal extremities 87 and 88. It also is provided with a large bore lumen 
89 extending the length thereof which has a suitable diameter such as 
0.070 inches and is particularly sized in such a manner so that there is 
formed an annular space 91 between the exterior surface of the flexible 
elongate member 66 and the interior of the flexible elongate member 86 
which can serve as a pulmonary artery pressure lumen. The annular space 91 
is in communication with a pulmonary artery port 92 provided in the side 
wall of the flexible elongate member 86 adjacent the distal extremity 88 
thereof. 
A toroidal piezoelectric ultrasonic transducer 93 is mounted on the distal 
extremity of the outer catheter 63. The transducer 93 is formed in the 
same manner as the transducer 21 in FIGS. 1-4. As described therein, the 
transducer 93 is formed as a toroid having a convex surface facing towards 
the distal extremity of the inner catheter 62. An epoxy backing material 
94 of the type hereinbefore described is provided behind the transducer 
93. A small wire lumen 96 is provided in the side wall of the flexible 
elongate member 86 and receives the wires 97 connected to the transducer 
92. 
A fitting 101 is mounted on the proximal extremity 87 of the flexible 
elongate member 86 forming a part of the outer catheter 63 and is formed 
of a suitable material such as plastic. The fitting 101 is provided with a 
central bore 102 which is in communication with the lumen 89 provided in 
the outer catheter 63. The fitting 101 is provided with a leg 103 through 
which the wires 97 extend and which are connected to an electrical 
connector 104. The fitting 101 is provided with another leg 106 which is 
provided with a Luer-type fitting 107 and has a passage which is in 
communication with the main bore 102. The fitting 101 is provided with a 
threaded bore 108 which is coaxially aligned with the bore 102. A threaded 
shaft 109 is threaded into the threaded bore 108. The shaft 109 is 
provided with a conical distal extremity which is adapted to come in 
engagement with an O-ring 111 disposed within the threaded bore 108 and 
encircling the threaded bore. The threaded shaft 109 is provided with a 
knob 112 to facilitate rotation of the shaft. The threaded shaft is 
provided with a bore 113 extending axially thereof and which is in 
communication with the bore 102. The inner catheter 62 is adapted to be 
inserted into and withdrawn from the bore 113. A two-armed adapter or 
fitting 116 is mounted on the proximal extremity 67 of the catheter 62. 
The side arm 117 is in communication with the balloon inflation lumen 72 
and the central arm 118 is in communication with the distal lumen 73. 
Operation and use of the embodiment of the device shown in FIGS. 1-3 for 
measuring volumetric blood flow in a vessel and, more specifically, 
cardiac output may now be briefly described as follows. The catheter 11 
can be inserted into the human body in a substantially conventional 
manner. The catheter 11 is connected to the appropriate monitoring 
equipment (not shown). The catheter 11 is then introduced by a 
percutaneous technique through a suitable needle or sheath (not shown) 
into a large vein. The catheter 11 is then gently advanced until the tip 
has been advanced into the superior vena cavae 121 of the heart 122 as 
shown in FIG. 11. Alternatively, if desired, the catheter 11 can be 
introduced into the inferior vena cavae 123. At this point, the balloon 16 
is inflated with air or carbon dioxide to an appropriate volume of 1.5 cc. 
The balloon and catheter distal extremity are thereafter floated through 
the right atrial chamber 124 through the tricuspid valve 126, into the 
right ventricle 127 of the heart and then through the pulmonary valve 128, 
through the main pulmonary artery 129 and out into the distal pulmonary 
artery 131. During the positioning of the catheter 11, the standard 
pressure measurements can be made by sensing the blood pressure through 
the lumen 17. In this way, the right atrial pressure, the right 
ventricular pressure, pulmonary artery pressure and pulmonary capillary 
wedge pressure can be measured. Pulmonary artery pressure may be measured 
through the port 27, in communication with the lumen 26. Right ventricular 
pressure may be simultaneously measured through port 29 in communication 
with the lumen 28. Since the port 27 is adjacent the transducer 21, the 
presence of a pulmonary artery waveform via lumen 26 confirms the position 
of the transducer 21 within the main pulmonary artery 129. Placement of 
the transducer 21 within the main pulmonary is critical for measurement of 
total cardiac output, since the entire cardiac output is ejected only 
through the main pulmonary artery. Monitoring the right ventricular 
pressure through the port 29 in communication with the lumen 28, while 
simultaneously monitoring the pulmonary artery pressure through the port 
27 via the lumen 26 assures that the transducer 21 is located within the 
main pulmonary artery 129 and not in a more distal pulmonary artery branch 
131. If the transducer 21 were located more distally in the pulmonary 
artery, the right ventricular port 29 would also reveal a pulmonary artery 
waveform, indicating that the catheter 11 needed to be withdrawn slightly 
to place the transducer 21 within the main pulmonary artery. 
Alternatively, should the right ventricular waveforms be noted through 
both ports 27 and 29, this would indicate that the transducer 21 needs be 
advanced slightly into the main pulmonary artery for accurate cardiac 
output measurements to be obtained. 
When an ultrasonic measurement of cardiac output is desired, electrical 
energy is suppled to the transducer at the proper frequency, as for 
example, 10 MHz As soon as this occurs, the crystal converts the high 
frequency energy to ultrasonic energy to create a large uniform 
cone-shaped beam 132 of ultrasound which beam extends forwardly in the 
vessel as shown in FIG. 11 and encompasses the entire main pulmonary 
artery 129. The first moment detection technique described in the 
co-pending application Ser. No. 036,796 filed on Apr. 10, 1987 is utilized 
to measure absolute flow through this sample volume which is being 
monitored by the use of the large uniform beam of ultrasound. The lumen 17 
extending through the distal extremity of the catheter is used to make 
pulmonary capillary wedge pressure measurements, simultaneous with 
pulmonary artery pressure measurements via lumen 28, right ventricular 
pressure measurements via lumen 26 and cardiac output measurements via the 
ultrasonic transducer 21 and appropriate circuitry. 
By utilizing a large uniform beam to encompass the interior of the entire 
main pulmonary artery, the information obtained from the uniform beam can 
be utilized with the first moment detection technique in connection with 
the computational constant previously described in co-pending application 
Ser. No. 036,796 filed on Apr. 10, 1987, to give a true volumetric flow 
through the sample volume in the main pulmonary artery. The method of the 
present invention can make such volumetric flow measurements with a single 
transducer having the particular convex shape to provide a large uniform 
beam of isonification without knowledge of the size of the vessel, the 
angle of incidence between flow and the ultrasonic beam, the velocity 
profile within the vessel, or the exact location of the transducer 21 
within vessel of interest. 
Operation use of the embodiment of the invention shown in FIGS. 5 and 6 is 
very similar to that hereinbefore described with the embodiment shown in 
FIGS. 1-4. 
Operation and use of the catheter assembly 61 shown in FIGS. 7-10 is as 
follows. The knob 112 is unscrewed to allow easy withdrawal of the 
catheter 62 into the body of the outer catheter 63 until the balloon 71 is 
in proximity of the transducer 93. The knob 112 may now be tightened, 
compressing the O-ring 111 and preventing backflow of blood from the 
annular space 91. The entire catheter assembly 61 can now be inserted into 
the human body in the conventional manner previously described. The 
catheter 61 is then gently advanced until the tip has been advanced into 
the superior vena cavae 121 or the inferior vena cavae 123 of the human 
heart 122. At this point, the balloon 71 is inflated, as previously 
described, and the catheter and distal extremity are thereafter floated 
through the right atrium 124, tricuspid valve 126, right ventricle 127, 
pulmonary valve 128 and into the main pulmonary artery 129 in the manner 
previously described. 
At this point, the pulmonary artery waveform tracings may be simultaneously 
obtained through the distal lumen 73 and the proximal pulmonary artery 
port 92 in communication with the annular space 91. The knob 112 may be 
unscrewed, and the inner catheter 62 with the balloon 71 still inflated 
may be advanced into the distal pulmonary artery 131 while the outer 
catheter 63 is held in place, thus keeping the transducer 93 in place 
within the main pulmonary artery 129. The catheter 62 is advanced until a 
pulmonary capillary wedge pressure waveform is obtained via the distal 
lumen 73. At this point, the knob 112 may be retightened, preventing 
backflow of blood from the port 92 via the annular space 91. At this 
point, simultaneous pulmonary capillary wedge pressure, and pulmonary 
artery pressure are available via distal lumen 73 and annular space 91 
respectively. The principal advantage of the present embodiment is that 
the distance between the balloon 71 and the transducer 93 carried on the 
distal extremity of the outer catheter 63 can be varied merely by shifting 
the position of the inner catheter 62 with respect to the outer catheter 
63. 
Accurate flow measurements may now be obtained by connecting the catheter 
assembly 61 to the electrical system which is disclosed in co-pending 
application Ser. No. 036,796 filed on Apr. 10, 1987. By varying the 
distance between the balloon 71 and the transducer 93 it is possible to 
obtain an accurate measurement of the distal pulmonary capillary wedge 
pressure where the balloon is positioned, and still retain the transducer 
93 in the main pulmonary artery for accurate cardiac output measurements. 
The pressure which is measured by the pulmonary artery port 92 indicates 
the location of the transducer. The distal pressure which is measured at 
the distal extremity just beyond the balloon 71 indicates the location of 
the balloon. The exact position of the pulmonary artery port 92 is 
important in that the transducer should be located just distal to the 
pulmonary valve within the main pulmonary artery 129. This can be readily 
ascertained because as the pulmonary artery port passes through the 
pulmonary valve there will be a change in waveform to indicate the proper 
location for the transducer 93. 
Thus it can be seen that it is possible to make cardiac output measurements 
in the main pulmonary artery and simultaneously make pressure measurements 
distal of the main pulmonary artery at distances which need not be fixed 
with respect to the transducer 93. In this way it is possible to 
compensate for the different distances between main pulmonary artery and 
capillary wedge positions which occur in the anatomy of various persons. 
With the embodiment shown in FIG. 1 it is not possible to accommodate the 
different dimensions which can be encountered in the human anatomy. In 
addition, the present embodiment makes it possible to eliminate the use of 
an independent lumen for pressure measurements since the annular space 91 
between the catheters 63 and 62 is used for such a measurement. 
From the foregoing it can be seen that a pulmonary artery catheter has been 
provided which permits a measurement of instantaneous cardiac output while 
utilizing a transducer capable of propagating a large uniform beam within 
the main pulmonary artery. In addition by utilizing the coaxial 
construction, independent pulmonary capilliary wedge pressure measurements 
may be made simultaneously with cardiac output measurements.