Venous pulse oximetry
First Claim
1. A method of non-invasively measuring venous oxygen saturation, comprisingapplying a pressure transducer at a first site on a body having venous and arterial systems,applying a drive signal to the pressure transducer at a predetermined frequency, to cause a series of pulsations of a predetermined magnitude in the venous blood volume in the vicinity of said first site, the magnitude of the pulsations being adjusted such that the arterial system is minimally disturbed,applying an oximeter device at a second site on the body,measuring output signals received from said oximeter device, said output signals containing a component representative of the modulation of venous blood volume due to said pulsations,deriving a measure of venous oxygen saturation from the frequency response of said output signals.
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Accused Products
Abstract
A method of non-invasively measuring venous oxygen saturation, comprising: applying a pressure transducer at a first site on a body, applying a drive signal to the external pressure transducer at a predetermined frequency, to cause a series of pulsations of a predetermined magnitude in the venous blood volume in the vicinity of said first site, applying an oximeter device at a second site on the body, measuring output signals received from said oximeter device, said output signals containing a component representative of the modulation of venous blood volume due to said pulsations, deriving a measure of venous oxygen saturation from the frequency response of said output signals.
161 Citations
18 Claims
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1. A method of non-invasively measuring venous oxygen saturation, comprising
applying a pressure transducer at a first site on a body having venous and arterial systems, applying a drive signal to the pressure transducer at a predetermined frequency, to cause a series of pulsations of a predetermined magnitude in the venous blood volume in the vicinity of said first site, the magnitude of the pulsations being adjusted such that the arterial system is minimally disturbed, applying an oximeter device at a second site on the body, measuring output signals received from said oximeter device, said output signals containing a component representative of the modulation of venous blood volume due to said pulsations, deriving a measure of venous oxygen saturation from the frequency response of said output signals.
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14. Apparatus for non-invasively measuring venous oxygen saturation comprising:
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a pressure transducer for applying a series of pulsations to a first site on a body having venous and arterial systems, a pulse oximeter, control means for controlling the frequency and/or magnitude of said pulsations, such that the venous blood volume is modulated, the control means being operable to adjust the magnitude of the pulsations such that the arterial system is minimally disturbed, signal processing means for extracting a value for venous oxygen saturation from signals received from said oximeter, said signals containing a component representative of a modulation of venous blood volume due to said pulsations. - View Dependent Claims (15, 16, 17)
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18. A method of non-invasively measuring venous oxygen saturation, comprising
applying a pressure transducer at a first site on a body, applying a drive signal to the pressure transducer at a predetermined frequency, to cause a series of pulsations of a predetermined magnitude in the venous blood volume in the vicinity of said first site, applying an oximeter device at a second site on the body, measuring output signals received from said oximeter device, said output signals containing a component representative of the modulation of venous blood volume due to said pulsations, deriving a measure of venous oxygen saturation from the frequency response of said output signals, wherein the magnitude of the pulsations is determined by progressively increasing the pulsation magnitude and observing a frequency spectrum of the measured output signals, the appearance of a multiplicative term in the frequency spectrum, indicative of a disturbance to the arterial system, indicating that the maximum permissible magnitude has been reached and wherein, upon reaching the point where said multiplicative term appears, the pulsation magnitude is subsequently reduced to a point where the multiplicative term becomes insignificant.
Specification