METHOD AND SYSTEM FOR MEASURING PULMONARY ARTERY CIRCULATION INFORMATION

• US 20090131765A1
• Filed: 11/17/2008
• Published: 05/21/2009
• Est. Priority Date: 11/16/2007
• Status: Active Grant

• Current Assignee: EKOS Corporation (Boston Scientific Corporation)
• Original Assignee: Broncus Technologies, Inc
• Inventors: LEVIN, Philip Stephen, ROSCHAK, Edmund J., SCHWARDT, Jeffrey
• Granted Patent: US 8,323,202 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• CPC Class Codes: A61B 8/04 Measuring blood pressure
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: A61B 8/4483 characterised by features of the ultrasound transducer
• CPC Class Codes: A61B 8/488 involving Doppler signals

Abstract

Minimally invasive systems and methods are described for measuring pulmonary circulation information from the pulmonary arteries. A transbronchial Doppler ultrasound catheter is advanced through the airways and in the vicinity of the pulmonary artery. Doppler ultrasound energy is sent through the airway wall and across the pulmonary artery to obtain velocity information of blood flowing through the artery. The velocity information is used to compute pulmonary circulation information including but not limited to flowrate.

Claims

1. A medical system for measuring pulmonary circulation information of the pulmonary artery comprising:

a catheter comprising a flexible shaft and a distal section, said distal section comprising at least one ultrasonic transducer; and

an ultrasound Doppler signal processing unit comprising;

an output port for delivering outgoing electrical signals to said at least one ultrasonic transducer;

an input port for receiving incoming electrical signals from said at least one ultrasonic transducer;

a processor in communication with said output port and said input port and configured (a) to control the outgoing electrical signals delivered to said ultrasonic transducer;

(b) to receive and analyze the incoming electrical signals for volumetric flowrate (Q) of the pulmonary artery using Doppler shifting and time of flight analysis;

(c) to determine a precursor pressure signature of the fluid in the pulmonary artery using Doppler shifting; and

(d) to identify a pulmonary arterial pressure (PAP) by comparing said precursor pressure signature with a set of predetermined pressure signatures wherein each of said predetermined pressure signatures has an associated mean pulmonary arterial pressure.

2. The system of claim 1 wherein said catheter comprises a longitudinal axis, and said at least one ultrasonic transducer comprises a first transducer having a first angle with respect to said axis of said catheter, and a second transducer having a second angle with respect to said axis of said catheter and said first angle and said second angle are different.

3. The system of claim 1, wherein said processor is further configured to calculate a TPR ratio where the TPR ratio is proportional to PAP and inversely proportional to Q.

4. The system of claim 2, wherein the outgoing and incoming ultrasonic signals are analyzed to determine velocity (V) and a diameter (D) of the pulmonary artery, and further determining Q based on V and D.

5. The system of claim 1 further comprising a bronchoscope through which said catheter is inserted.

6. The system of claim 4 further comprising a visual display adapted to display at least of V and Q.

12. The method of claim 1 wherein the discrete area is annulus

13. The method of claim 12 further comprising identifying the center of the blood vessel prior to determining the step of computing a plurality of component flowrates.

16. The method of claim 12 wherein said analyzing step is based at least in part on a slant angle, said slant angle equal to an angle formed between the distal end of said catheter and a normal vector, said normal vector being normal to a central axis of the blood vessel.

7. A method for determining pulmonary circulation information in a pulmonary artery of a patient without puncturing or opening the pulmonary artery, said method comprising:

providing an ultrasound Doppler catheter, said catheter comprising a distal section and at least one ultrasound transducer in said distal section;

advancing said distal section of said ultrasound Doppler catheter through a natural respiratory opening, and into an airway and to a location along an airway wall such that at least a portion of said distal section and said at least one ultrasound transducer is in proximity of the pulmonary artery;

sending and receiving ultrasonic waves to said pulmonary artery from said ultrasound transducer;

determining a measured pressure signature by analyzing the received ultrasonic waves and

comparing the measured pressure signature to one or more predetermined pressure signatures wherein each of said predetermined pressure signatures has an associated mean pulmonary arterial pressure.

8. The method of claim 7 wherein the one or more predetermined pressure signatures and associated mean arterial pressure are determined based on empirical data arising from directly measuring the mean pulmonary arterial pressure in a blood vessel of a participant subject with a sensor for a plurality of different precursor pressure signatures.

9. A transbronchial method for determining flowrate in a blood vessel in the thoracic cavity, said method comprising the steps of

providing an ultrasound catheter, said catheter comprising a distal section and at least one ultrasound transducer in said distal section;

advancing said distal section of said catheter through a natural respiratory opening, and into an airway such that at least a portion of said distal section and said at least one ultrasound transducer is in proximity of the blood vessel;

sending ultrasound energy along a path across a tissue region, said tissue region including said blood vessel; and

analyzing reflected ultrasound energy to determine flowrate in said blood vessel.

10. The method of claim 9 wherein said analyzing comprises determining an instantaneous velocity profile across the tissue region, and computing an instantaneous flowrate in the blood vessel based on said instantaneous velocity profile.

11. The method of claim 10 wherein said instantaneous flowrate is calculated by, at least in part, computing a plurality of component flowrates corresponding to a plurality of discrete area cross sections across the tissue region.

14. The method of claim 9 further comprising determining a temporal flowrate by obtaining a plurality of instantaneous flowrates over a sampling duration and time-averaging said instantaneous flowrates over said sampling duration.

15. The method of claim 14 wherein said sampling duration is between 6 to 10 seconds.

17. The method of claim 9 wherein said ultrasound catheter operates using a sampling range sufficient to detect zero velocity in tissue proximal and distal to the blood vessel, and said sampling range being greater than the diameter of the blood vessel.

18. The method of claim 9 wherein said flowrate is determined without measuring an actual diameter of the blood vessel.

19. The method of claim 9, wherein the blood vessel is a pulmonary artery, and further comprising determining a mean PAP in the pulmonary artery, wherein said mean PAP is determined using ultrasonic waveform analysis and comprises comparing a measured pressure signature to a predetermined pressure signature.

20. The method of claim 19 further comprising calculating the TPR.