FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF INVENTION:-“A SYSTEM AND METHOD FOR MEASURING CARDIAC OUTPUT”
2. Patent Application NO.220/CHENNAI/2006 dated 10.2.2006
2.APPLICANT:- LARSEN & TOURBO LIMITED, LARSEN &
TOURBO LIMITED, KIADB • Industrial Area, Hebbal-
Hootagalli, Mysore-570 018, an Indian National, A
company registered under Companies Act.
3.INVENTORS:-
a)V. Ronald Lewis
b) Mr.Vishwanath P.Nayak
c)Mr.Tejas Bengali,
d)Mr.Kamal Agarwal
e)Mr.Ravindran N
(b)NATIONALITY:-Indian
(c)ADDRESS:- LARSEN & TOURBO LIMITED, KIADB Industrial Area, Hebbal-Hootagalli, Mysore-570 018
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed
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4.DESCRIPTION
TECHNICAL FIELD
The present invention relates to apparatus and method for measuring cardiac output in mammals, particularly human. More particularly, the present invention relates to apparatus and method for measuring cardiac output by thermodilution method.
BACKGROUND ART
Measuring cardiac output using thermodilution is known and generally used in this field. The determination of cardiac output, or measurement of the blood volumetric output of the heart is important for a variety of medical situations. The cardiac output information along with a number of additional factors such as pulmonary factors are used generally to evaluate the condition of the subject's heart. Even with the variety of approaches developed for measuring this output, each exhibit certain limitations and/or inaccuracies.
Generally, in thermodilution method, a cold bolus of saline at ice or room temperature in an amount of about 5-10 milliliters is injected through the catheter
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into the right auricle of the subject's heart. The injectate mixes with the blood to produce a temperature drop in the blood- The temperature of the injectate and blood downstream to the right auricle is monitored. A computer is used to process the data of temperature of the injectate before injection and the temperature of the blood stream after mixing with the injectate.
The measurement procedure requires about two minutes to complete. For purposes of gaining accuracy, this procedure is repeated three or four times and readings are averaged.
The upstream temperature measurement of the injectate is generally carried out using a thermistor permanently mounted in the conduit, which supplies the injectate. However, the conduit should be sterile and disposable, which is expensive.
This problem is solved by US Patent No. 633 6902 that discloses a system for sensing a characteristic of fluid flowing to or from a body. The system disclosed has conduit, a first end of the conduit adapted to be outside the body, a second end adapted to be received with the body, and a flow passage through which the
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fluid flow between the first and second ends. A probe including a sensor for sensing a characteristic of the fluid is mounted on the conduit with the sensor in the flow passage. The sensor is isolated from the fluid flowing in the flow passage. The patent suggests that by removably mounting the proble on the conduit, at least the portion of the conduit can be disposed without disposing the probe. Further, it is suggested that as the sensing means is isolated from the fluid in the flow passage, the probe need not be sterile.
The system uses a syringe to check valve for substantially preventing the flow of fluid towards the direction of the inlet. However, the manual operation errors are expected and hence the accuracy of the measurement of cardiac output is substantially low. Also the cost of the system very high to be affordable for a common man in India. Although inventor of this patent 6336902 claims that by using non-contactable probe described in much cost effective because of no-need of sterilizing, the injectate will attack thermistor etc, it is found that this need not be true.
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Since whatever cables and sensors taken inside the operation theater and used on the patient are supposed to be sterile, using a sterilazable probe is much safer than using non-sterilazable probe. Also by enclosing the thermistor inside a USP CLASS VI body fluid compatible, implant grade material like AS316L/AS316Q will not corrode the thermistor. The speed of thermistor response to change in temperature can be increased by using fast temperature detection algorithms generally available and used in clinical thermometers. Also gold plating on SS316 tube will increase the thermal conductivity.
US Patent No. 5354272 which is issued to BAXTER international USA, also discuses a similar method without much improvement in the art.
US Patent No. 6248077 granted to Edwards life sciences USA, also discloses a reusable temperature sensor installed in the system and says only about using a thermistor in the probe. But recent advances in clinical thermometry confirms that using a non-contact infrared thermometer is much better, faster, and accurate than this invention.