Method and apparatus to determine an initial flow rate in a conduit
A method and apparatus for determining an initial flow rate in a conduit is disclosed. A known change is made to the flow to be measured, resulting changes (or values corresponding to these changes), or relative changes in the flow to be measured are monitored and the initial flow in the conduit is calculated from the value of the known change and monitored changes. Devices to practice the method include catheters having one or two sensors and one or two sites for introducing the volume change.
1. A method for determining an initial flow rate in a conduit, comprising:
(a) introducing a volume change to the initial flow rate at a location, the introduced volume change predominately flowing retrograde to an initial flow in the conduit, producing a resulting change upstream of the location; and
(b) determining the initial flow rate corresponding to the introduced volume change and the resulting change.
2. The method of claim 1 , further comprising measuring a resulting change upstream from the location.
3. A method of determining an initial flow rate in a conduit, comprising:
(a) determining the initial flow rate corresponding to the following equation and analogous relationships,
Q
=
Qi
Cd
-
Cu
,
where Qi is the volume change flow rate, Cd is the relative change in a flow corresponding parameter downstream from a location of flow change, Cu is the relative change in a flow corresponding parameter upstream from the location of the flow change, and a Q is the initial flow rate.
4. A method for determining an initial flow rate in a conduit, comprising:
(a) determining the initial blood flow rate corresponding to the following equation and analogous relationships,
Qh
=
Qi
Cd
,
where Qh=initial flow rate, Qi=a flow rate of the volume change
Cd
=
Δ
Qd
Qd
,
ΔQd=change in a downstream flow rates and Qd is the downstream flow rate.
5. A method for determining an initial flow rate in a conduit, comprising:
(a) determining the initial flow rate corresponding to the following equation and analogous relationships,
Qc
=
Qi
Cu
,
where Qc=the initial flow rate, Qi=the flow rate of the volume change and Cu=the relative change in a flow corresponding parameter upstream of a location of the volume change.
6. A method for determining an initial flow rate and a conduit, comprising:
(a) determining the initial flow rate corresponding to the following equation and analogous relationships
Qv
=
Qi
Cd
+
1
,
where Qi=the flow rate of the volume change, Cd=the relative change in a flow corresponding parameter downstream of a flow change, and Qv=is the initial flow rate.
7. An apparatus for determining an initial flow rate in a conduit, comprising:
(a) a catheter having an upstream port and a downstream port;
(b) means for introducing a volume change through the upstream port and the downstream port;
(c) a velocity sensor located external to the conduit; and
(d) a controller connected to the means for introducing volume change and the velocity sensor, the controller configured to determine the initial flow rate.
8. A method for determining an initial flow rate in a conduit, the method comprising:
(a) introducing a constant rate infusion into the initial flow;
(b) introducing a first volume change to the initial flow upstream of a sensor;
(c) introducing a second volume change to the initial flow downstream of the sensor; and
(d) determining the initial flow rate corresponding to the first volume change and the second volume change.
9. An apparatus for determining an initial flow rate in a conduit, comprising:
(a) a catheter having an infusion port, a volume change port, an upstream sensor intermediate the infusion port and the volume change port, and a downstream sensor located downstream of the volume change port;
(b) means for introducing a constant infusion through the infusion port;
(c) means for introducing a volume change through the volume change port; and
(d) a controller connected to the upstream sensor and the downstream sensor for determining the initial flow rate corresponding to the introduced volume change.
10. An apparatus for determining an initial flow rate in a conduit, comprising:
(a) a catheter having a pair of volume change ports, a sensor intermediate the volume change ports and an infusion port upstream of the pair of volume change ports;
(b) means for introducing a constant infusion through the infusion port;
(c) means for introducing a first volume change through one of the volume change ports and a second volume change through a remaining one of the volume change ports; and
(d) a controller connected to the sensor for determining the initial flow rate corresponding to the introduced volume changes.