Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/06—Measuring blood flow
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/12—Diagnosis using ultrasonic, sonic or infrasonic waves in body cavities or body tracts, e.g. by using catheters
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/44—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
  • A61B8/4444—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device related to the probe
  • A61B8/445—Details of catheter construction

Definitions

• Measurement of cardiac output is crucial in the care of critically ill patients such as patients with multiple trauma, patients in over ⁇ whelming sepsis, and patients with acute myocardial infarction. In the case of patients with acute myocardial infarction, there is a worsening prognosis with decrease in cardiac output.
• Knowledge of the cardiac output provides information useful in determining the clinical state of a given patient and in rationally planning therapy for the patient. Such information is not contained in the usually measured vital signs. For example, a low mean arterial pressure with elevated pulse does not adequately distinguish between cardiogenic and septic shock, the treatments for which are quite different. Consequently, a method that distinguishes between cardiogenic and septic shock would be important in planning appropriate therapy. The measurement of cardiac output, in this case, would provide valuable information that would allow an appropriate diagnosis to be made.
• thermodi . lution The importance of knowing cardiac output has led to many methods for its determination.
• a catheter In the thermodilution method a catheter is placed into the central venous circulation, usually by percutaneous entry into the internal jugular or subclavian vein.
• Transcutaneous ultrasound has also been used. Ultrasound transducers are placed externally on the body at the suprasternal notch. Under the most sanguine circumstances, at least 10% of patients cannot have their cardiac outputs measured in this way. Many difficulties with this approach have been reported: repeated measure ⁇ ments may lead to varying location of the sample volume that is scanned, there are changes in the angle of intersection of the ultrasound.beam • with the axis of the vessel, capability for continuous measurement of the cardiac output is not available, and other major thoracic vessels may interfere with the Doppler ultrasound signals. Further, the method is not,feasible in many important clinical settings in which .the patients are not cooperative or are in the operating room, where the suprasternal notch may not be accessible.
• urine output cannot be correlated with perfusion of major organs.
• the primary object of the invention is to provide a method and apparatus for continuously and accurately measuring cardiac output in a major discharge artery of a mammalian heart, most notably the human heart, without invasion of any j closed anatomical cavity or system and without surgery.
• the method of the invention comprises placing a sound transducer in great proximity to the aorta or pulmonary artery of the heart of the mammal by passing a probe carrying the transducer into the trachea and transmitting ultrasound waves from the transducer toward the path of flow of blood in the artery.
• the probe can be passed through the nasal or oral cavity, past the epiglottis into the trachea or, in the case of patients who have had a tracheostomy, directly into the trachea through the surgical
• Figure 3 is a horizontal sectional view of the trunk of a human taken at the level of the tracheal bifurcation and shows the close relationship between the trachea and the aorta and the pulmonary arteries.
• Figure 4 is a perspective view of the probe of the present invention with one end cut away in axial section to show the transducer mounting and orientation with respect to the axis of the tube.
• Figure 5 is a schematic view of the trachea and the aorta and shows the location and orientation of the probe and transducers with respect to the path of flow of blood in the aorta.
• Figure 6 is a schematic view and block diagram showing the orientation and relationship of the transducers. The electrical conductors running the length of the tube to the ultrasound generating and receiving device are also shown.
• the apparatus of the preferred embodiment consists of a probe with a piezoelectric transducer mounted at one end and electrical conductors extending the length of the probe for connection to conventional directional pulsed or continuous wave Doppler ultrasound hardware, such as that described by Hartley et al. in the Journal of Applied Physiology, October 1974, and by Keagy et al. in the Journal of Ultrasound Medicine, August 1983. Modifications to the signal output can be made to display blood flow volume rate, aorta or other vessel diameter, blood velocity and other selected displays.
• the probe 10 is shown in Figures 1, opening.
• the reflected ultrasound waves are received by the transducer and the average Doppler frequency difference between the transmitted waves and the reflected waves is measured.
• the cross-sectional size or area of the artery at the point of ultrasound reflection is measured and the volumetric blood flow rate is determined from such measurements.
• the transducer is oriented to transmit and receive ultrasound waves in a direction within the range of 10° - 80° with respect to the direction of the path of flow of blood in the artery.
• the apparatus of the invention is a trachael probe comprising a flexible tube of sufficient length to extend from the oral or nasal cavity or from a surgical trachael opening, through the trachea to the bifurcation thereof, with an ultrasound transducer mounted on the tube in proximity to one end and disposed to transmit in a direction within the range of 10° - 80° with respect to the axis of the tube. Electrical conductors extend from the transducer the length of the tube. A second transducer can also be mounted on the tube.
• Figure 1 is a front to back vertical sectional view of the upper portion of the human body showing the nasal and oral cavities and the pathway through the trachea to the bifurcation thereof.
• the heart is shown in left lateral or side view.
• the trachea probe of the invention is shown in position in the trachea with the transducer(s) in great proximity to the aorta.
• Probe 10 consists of flexible plastic tubing 11 roughly three to four feet long and about one-fourth inch in outside diameter. The length must be sufficient to extend from outside the body to the vicinity of the heart through the trachea entering either through the nasal or oral cavity, or through a surgical opening in the case of patients who have had a tracheotomy.
• two piezo ⁇ electric transducers or chips 21 and 22 are mounted to the exterior of tube 11 at one end in a mounting medium 23.
• Transducer 21 is used to collect Doppler data for velocity calculation and transducer 22 is used to collect data for calculation of the diameter of the artery at the point of velocity measurement, although data for diameter measurement can also be collected, though less critically, using transducer 21.
• Electrical conductors 24, 25, 26 and 27 extend the length of tube 11 for connection to the conventional Doppler ultrasound hardware 28.
• Piezoelectric transducers 21 and 22 are directional in ultrasound transmission and are oriented as shown in Figure 6.
• Transducer 21 is oriented to transmit and receive ultrasound in a direction 45° with respect to the axis of tube 11, and transducer 22 is oriented to transmit and receive ultrasound in the same plane (i.e. in the plane defined by the axis of tube 11 and the direction of ultrasound transmission from transducer 21) but 90° with respect to the axis of tube 11.
• the angle of ultrasound transmission from transducer 21 with respect to the axis of tube 11 is designated ⁇ (See Figure 6). In the preferred embodiment ⁇ is 45° but the angle may vary in the range of 10° - 80°.
• piezoelectric transducer 21 can be directed in either direction of the axis of tube 11, i.e., either toward or away from transducer 22, resulting in ultrasound transmission either generally up-stream or generally down-stream of the blood flow path in the artery.
• the spacing or distance between transducer 21 and transducer 22 is a function of the angle and the diameter of the vessel, such as the aorta or pulmonary artery, in which the blood flow measurement is being made,* so that the diameter data utilizing transducer 22 and the velocity data utilizing, transducer 21 are taken in the same plane across the artery. This insures that the volume computation (velocity x cross-sectional area) is accurate. More specifically, the distance, D, (See Figure 6) is the estimated diameter, d , of the vessel at the point of measurement (transducer 22) divided by 2 times the tangent of ⁇ , or d
• Electrical conductors 24, 25, 26 and 27 extend the length of tube 11 and must be capable of transmitting ultra high frequency electrical signals (up to 20 mega Hertz) without significant attenuation.
• an electrical connector such as that disclosed in the Furler patent (4,369,794) can be used.
• the method relies on the anatomical discovery or fact that the aorta and pulmonary artery are located adjacent the trachea just above the bifurca ⁇ tion thereof, and that a transducer placed in the trachea can be directed toward the selected artery and accurate blood flow measurements made without significant interference.
• access to the trachea, T, of a human, H can be had in accordance with standard medical practice through the nasal cavity, -
• a transducer or transducers placed in the trachea as shown in Figure 1 can be directed to transmit and receive ultrasound waves through the wall of the trachea and through the wall of the aorta or the pulmonary artery to be reflected by the blood flowing in the selected • artery and, due to the movement of the blood, cause a Doppler shift in the frequency of the reflected waves as compared to the frequency of the transmitted waves.
• the ultrasound waves are also reflected by the near and far walls of the artery and such reflection can be used for diameter measurement of the artery.
• probe 10 is placed to locate transducers 21 and 22 in the trachea, T, pointing toward the selected artery, such as the aorta, A, as shown in Figure 5.
• the position of probe 10 and transducers 21 and 22 can be adjusted until the maximum Doppler shift is obtained and the position can also be checked or confirmed by X-rays to insure placement for optimum data collection.
• the volumetric flow rate, Q can be determined as follows:
• the disadvantage in this procedure is that the diameter determination is not made at the intersection of the ultrasound transmission with the center of the artery, and ⁇ must be assumed to be the same as ⁇ , which results in some lack of precision in the velocity and volume calculations. Nevertheless, determinations using one transducer only are accurate enough to be useful.
• the foregoing method can be used during Cardio Pulmonary Resucitation (CPR) to determine the effectiveness of CPR; to determine blood acceleration as well as flow rate; to obtain a blood velocity profile across the artery, such as the aorta, by range gating; to measure the variation in artery dimension during pulsatile flow; and to obtain a stroke-volume measurement of cardiac output.
• CPR Cardio Pulmonary Resucitation
• a large number of patients who require continuous measurement of cardiac output have significant associated clinical problems. Often such patients have multiple systems organ failure, overwhelming sepsis, significant trauma to many major organ systems, decompensated congestive heart failure, or major myocardial infarction.
• Such patients often have an endotrachael tube in place because of such problems.
• use of general anesthesia requires the presence of an endotrachael tube for the maintenance of the patient's airway.
• an endotrachael tube is often in place for the night following surgery.
• Patients suffering major trauma are routinely intubated following significant thoracic trauma, significant head injury, or multiple abdominal injuries.
• Patients in multiple systems organ failure, septic shock, or hemorragic shook have endotracheal tubes in place to assist ventilation during acute decompensation and in the immediate resuscitation phase.
• the method of the present invention provides for measurement of cardiac output at optimum locations without major surgical procedure or invasion of a closed body system.
• No major body cavity not routinely in communication with the external environment is required.
• No major or minor surgical procedure is required.
• No indwelling foreign body is necessary in the vascular system, a major body cavity, or in a major organ.
• No dye or radioactive substance is necessary for the measurement to be performed, and no air emboli are introduced. Continuous monitoring is also possible.

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• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Heart & Thoracic Surgery (AREA)
• Medical Informatics (AREA)
• Biophysics (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Pathology (AREA)
• Radiology & Medical Imaging (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Veterinary Medicine (AREA)
• Physics & Mathematics (AREA)
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• Animal Behavior & Ethology (AREA)
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• Ultra Sonic Daignosis Equipment (AREA)
• Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)

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• 1986
  • 1986-01-13 JP JP61500707A patent/JPS62501682A/ja active Pending
  • 1986-01-13 EP EP19860900923 patent/EP0208771A4/fr not_active Withdrawn
  • 1986-01-13 WO PCT/US1986/000060 patent/WO1986004225A1/fr not_active Ceased

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