Method and apparatus for "zeroing" and calibrating a catheter-tip gauge-pressure transducer
First Claim
1. A method for first calibrating then zeroing a catherer-tip gauge-pressure transducer system having a pressure-sensitive diaphragm with a measurement side exposed to a pressure to be measured and a reference side normally exposed to atmospheric pressure, and haivng a display apparatus responsive to the diamphragm to provide an indication upon a calibratable scale of the pressure to be measured relative to atmospheric pressure said method comprising the steps of:
- (a) noting the pressure indicated by the display apparatus while the measurement side of the diaphragm is exposed to a pressure to be measured and the reference side of the diaphragm is exposed to atmospheric pressure;
then(b) substituting a known pressure for atmospheric pressure at the reference side of the diaphragm to produce a new pressure indication;
then(c) using the noted pressure indication of step (a), the known pressure of step (b), and the new pressure indication of step (b) calibrating the display apparatus scale in accordance with a calibration factor;
then(d) while establishing a constant reference pressure at the measurement side of the diaphragm, determining a mean value of the calibrated display-apparatus indication plus independently measuring a pressure substantially at the location of the reference side of the diaphragm;
then(e) calculating the difference between the independently measured pressure of step (d) and the calibrated display-apparatus indication of step (d);
then(f) adjusting the zero of the display apparatus in such a way as to cancel the difference calculated in step (e);
therein the display apparatus is calibrated, and is also zeroed for operation while the constant reference pressure is at the measurement side of the diaphragm.
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Accused Products
Abstract
Sensitivity or span calibration is adjusted to a desired value by (1) noting the display indication with the reference side of the transducer at atmospheric pressure, (2) substituting a known offset pressure for atmospheric pressure on the reference side, to produce a new display indication, and (3) adjusting the display to produce that amount of displacement (between the display indications in steps 1 and 2) which corresponds to the known offset pressure multiplied by the desired calibration value.
With the sensitivity or span calibration adjusted to a desired value, the zero point of the display is adjusted by (1) independently measuring the mean of the actual pressure, (2) noting the mean value of the display indication, and (3) adjusting the zero point to eliminate discrepancy between the mean value of the display and the mean of the actual pressure.
The apparatus has a port for a substitute reference pressure, and an external pressure gauge for measuring the mean pressure through an auxiliary lumen of the catheter.
91 Citations
29 Claims
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1. A method for first calibrating then zeroing a catherer-tip gauge-pressure transducer system having a pressure-sensitive diaphragm with a measurement side exposed to a pressure to be measured and a reference side normally exposed to atmospheric pressure, and haivng a display apparatus responsive to the diamphragm to provide an indication upon a calibratable scale of the pressure to be measured relative to atmospheric pressure said method comprising the steps of:
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(a) noting the pressure indicated by the display apparatus while the measurement side of the diaphragm is exposed to a pressure to be measured and the reference side of the diaphragm is exposed to atmospheric pressure;
then(b) substituting a known pressure for atmospheric pressure at the reference side of the diaphragm to produce a new pressure indication;
then(c) using the noted pressure indication of step (a), the known pressure of step (b), and the new pressure indication of step (b) calibrating the display apparatus scale in accordance with a calibration factor;
then(d) while establishing a constant reference pressure at the measurement side of the diaphragm, determining a mean value of the calibrated display-apparatus indication plus independently measuring a pressure substantially at the location of the reference side of the diaphragm;
then(e) calculating the difference between the independently measured pressure of step (d) and the calibrated display-apparatus indication of step (d);
then(f) adjusting the zero of the display apparatus in such a way as to cancel the difference calculated in step (e);
therein the display apparatus is calibrated, and is also zeroed for operation while the constant reference pressure is at the measurement side of the diaphragm. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for zeroing a medical catheter-tip pressure transducer system that has a pressure sensitive diaphragm, and that has a display apparatus which is responsive to provide an indication of the pressure to be determined at a location within a patient'"'"'s body, such display apparatus having adjustable zero;
- said method comprising the steps of;
(a) first calibrating the display apparatus; (b) after step (a), independently measuring the mean pressure substantially at such location; (c) after step (a), determining a mean value of the display-apparatus indication; and (d) using the mean value of the display-apparatus indication and the independently measured means pressure to adjust the zero of the display apparatus in such a way as to substantially eliminate discrepancy between the mean value and the mean pressure. - View Dependent Claims (9, 10, 11, 12, 13, 14)
- said method comprising the steps of;
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15. A method for first calibrating and then zeroing a medical catheter-tip gauge-pressure transducer system having a pressure-sensitive idaphragm with a measurement side exposed to a pressure to be measured and a reference side normally exposed to atmospheric pressure, and having display apparatus responsive to the diaphragm to provide an indication upon a calibratable and zero adjustable scale of the pressure to be measured, at a location within a patient'"'"'s body, relative to atmospheric pressure, said method comprising the steps of:
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(a) noting the pressure indicated by the display apparatus while the measurement side of the diaphragm is exposed to a pressure tO be measured at the location within a patient'"'"'s body and diaphragm is exposed to atmospheric pressure;
then(b) temporarily substituting a known pressure for atmospheric pressure at the reference side of the diaphragm to produce a new pressure indication;
then(c) using the noted pressure indication of step (a), the known pressure of step (b), and the new pressure indication of step (b) calibrating the display apparatus scale in accordance with a calibration factor;
then(d) independently measuring the mean pressure substantially at such location;
coincident with(e) determining a mean value of the calibrated display-apparatus indication while the reference side of the diaphragm is exposed to atmospheric pressure; and
then(f) using the determined mean value of the calibrated display-apparatus indication and the independently measured mean pressure to adjust the zero of the display apparatus in such a way as to substantially eliminate discrepancy between the determined mean value and the independently measured mean pressure. - View Dependent Claims (16, 17, 18, 19)
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20. Measuring apparatus for determining pressure at locations within a patient'"'"'s body, said apparatus comprising:
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electronic circuitry means, having calibratable scale expansion and adjustable zero, for providing an indication of the pressure; a catheter adapted to extend to such locations from outside such patient'"'"'s body and having; a first portion which, when the catheter is in use, in within such patient'"'"'s body and distal with respect to the circuitry means, a second portion which, when the catheter is in use, is outside such patient'"'"'s body and proximal with respect to the circuitry means, and at least two lumens defined within the catheter and communicating between its proximal and distal portions; a pressure transducer in the first portion of the catheter, the circuitry means being responsive to the transducer;
the pressure transducer having a measurement side that is exposed to the distal end of a first one of the two lumens;the first one of the two lumens being sealed at the distal portion against the pressure outside the catheter; and the other one of the two lumens being exposed at the distal portion to the pressure outside the catheter; and means for selectively connecting the first one of the two lumens, in its proximal portion, for communication with either; atmospheric pressure, for measurement of such gauge pressure within such patient'"'"'s body, or a known pressure source, to facilitate calibrating the scale expansion of the apparatus. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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27. In a method of zeroing a catheter-tip pressure transducer system having a catheter tipped with a pressure-sensitive diaphragm in pressure contact with living tissue, and having an adjustable-zero scale display apparatus responsive to the diaphragm, the method being
applying a reference pressure to the diaphragm of the transducer system; - then
observing the signal of the display apparatus responsive to the reference pressure;
thenzeroing the display apparatus at the reference pressure by bringing the signal into registry with a base line representing zero upon a scale; an improvement to the zeroing of said method comprising; independently of the diaphragm, measuring the pressure on the diaphragm at the point of its pressure contact with living tissue; and zeroing the display apparatus at the reference pressure by bringing the signal into registry with the level of the independently measured pressure upon the scale. - View Dependent Claims (28, 29)
- then
Specification