Cannula position detection
First Claim
1. A method for determining the position of a cannula inserted into the vascular system of a patient, the cannula coupled to the downstream end of a conduit that is connected at its upstream end to a reservoir of fluid, the method comprising the steps of:
- a. establishing a baseline pressure based on the pressure in the conduit when no flow of fluid is occurring;
b. moving a first predetermined quantity of fluid towards the upstream end of the conduit;
c. measuring the pressure in the conduit during the step of moving the predetermined quantity of fluid towards the upstream end;
d. moving a second predetermined quantity of fluid towards the downstream end of the conduit;
e. measuring the pressure in the conduit during the step of moving the predetermined quantity of fluid towards the downstream end;
f. summing the differences between the measured pressures and the baseline pressure;
g. normalizing the pressure difference sum by the predetermined quantity of fluid;
h. comparing the normalized sum to a predetermined range; and
i. providing an alarm if the normalized sum is outside the predetermined rangej. wherein steps (a), (f), (g), (h), and (i) are performed by a processor.
13 Assignments
0 Petitions
Accused Products
Abstract
Bidirectional flow patterns are induced in a fluid supply line and the reverse flow resistance and the forward flow resistance are measured and compared. A measure of the resistance to flow is made by normalizing a sum of the entire pressure response about a pressure baseline according to the volume of fluid in the bidirectional flow pattern. In the event that the cannula is positioned near or against the vessel wall, the resulting relatively large negative pressure response can indicate the positional irregularity. In one embodiment, a time period of zero flow is included between the positive and negative flow volumes to permit the system to stabilize.
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Citations
41 Claims
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1. A method for determining the position of a cannula inserted into the vascular system of a patient, the cannula coupled to the downstream end of a conduit that is connected at its upstream end to a reservoir of fluid, the method comprising the steps of:
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a. establishing a baseline pressure based on the pressure in the conduit when no flow of fluid is occurring; b. moving a first predetermined quantity of fluid towards the upstream end of the conduit; c. measuring the pressure in the conduit during the step of moving the predetermined quantity of fluid towards the upstream end; d. moving a second predetermined quantity of fluid towards the downstream end of the conduit; e. measuring the pressure in the conduit during the step of moving the predetermined quantity of fluid towards the downstream end; f. summing the differences between the measured pressures and the baseline pressure; g. normalizing the pressure difference sum by the predetermined quantity of fluid; h. comparing the normalized sum to a predetermined range; and i. providing an alarm if the normalized sum is outside the predetermined range j. wherein steps (a), (f), (g), (h), and (i) are performed by a processor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for determining the position of a cannula inserted into the vascular system of a patient, the cannula coupled to the downstream end of a conduit that is connected at its upstream end to a reservoir of fluid, the method comprising the steps of:
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a. moving a predetermined quantity of fluid towards the upstream end of the conduit; b. measuring the pressure in the conduit during the step of moving the predetermined quantity of fluid towards the upstream end; c. moving the predetermined quantity of fluid towards the downstream end of the conduit; d. measuring the pressure in the conduit during the step of moving the predetermined quantity of fluid towards the downstream end; e. computing the reverse resistance to the movement of the quantity of fluid towards the upstream end of the conduit based on the pressure measured during the step of moving the predetermined quantity of fluid towards the upstream end; f. computing the forward resistance to the movement of the quantity of fluid towards the downstream end based on the step of moving the predetermined quantity of fluid towards the downstream end; g. taking the difference between the forward resistance and the reverse resistance; and h. providing an alarm if the resistance difference is outside a predetermined range j. wherein steps (e), (f), (g), and (h) are performed by a processor. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A system for determining the position of a cannula inserted into the vascular system of a patient, the cannula coupled to the downstream end of a conduit that is connected at its upstream end to a reservoir of fluid and a flow control device engaged with the conduit to control the flow of fluid through the conduit, the flow control device occluding the conduit continuously, the system comprising:
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a pressure sensor for communication with the fluid in the conduit downstream of the occlusion provided by the flow control device, the pressure sensor for providing a pressure signal representative of the pressure of the fluid; a processor for; receiving the pressure signal provided by the pressure sensor; controlling the flow control device to stop flow in the conduit and establish a baseline pressure based on the pressure signal received from the pressure sensor during this period of stopped flow; controlling the flow control device to move a first predetermined quantity of fluid in the conduit in an upstream direction and a second predetermined quantity of fluid in a downstream direction; summing the differences between the pressure signals received from the pressure sensor during the upstream and the downstream flows of the predetermined quantity of fluid and the baseline pressure; normalizing the pressure difference sum by the predetermined quantity of fluid; and providing an alarm if the normalized sum is outside a predetermined range. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A system for determining the position of a cannula inserted into the vascular system of a patient, the cannula coupled to the downstream end of a conduit that is connected at its upstream end to a reservoir of fluid and a flow control device engaged with the conduit to control the flow of fluid through the conduit, the flow control device occluding the conduit continuously, the system comprising:
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a pressure sensor for communication with the fluid in the conduit downstream of the occlusion provided by the flow control device, the pressure sensor for providing a pressure signal representative of the pressure of the fluid; a processor for; receiving the pressure signal provided by the pressure sensor; controlling the flow control device to move a predetermined quantity of fluid in the conduit in an upstream direction and in a downstream direction; computing the reverse resistance to the movement of the quantity of fluid towards the upstream end of the conduit based on the pressure signal received during the movement; computing the forward resistance to the movement of the quantity of fluid towards the downstream end of the conduit based on the pressure signals received during the movement; determining the difference between the forward resistance and the reverse resistance; and providing an alarm if the resistance difference is outside a predetermined range. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41)
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Specification