Implantable chemical sensors for real-time clinical monitoring: progress and challenges

A blood parameter measurement device especially useful for surgical procedures includes a compact housing with a light source, light detector and signal converter contained within the housing. In use, the device is releasably coupled to a cassette that can be either used as an in-line cell in series with a cardiopulmonary by-pass circuit, or in another passageway that shunts the cardiopulmonary by-pass circuit. Preferably, the housing of the device has a longitudinal axis that extends in a direction generally parallel to the direction of blood flowing through the cassette.

Blood parameter measurement device

The present invention is directed towards apparatuses and methods for the automated measurement of blood analytes and blood parameters for bedside monitoring of patient blood chemistry. Particularly, the current invention discloses a programmable system that can automatically draw blood samples at a suitable programmable time frequency (or at predetermined timing), can automatically analyze the drawn blood samples and immediately measure and display blood parameters such as glucose levels, hematocrit levels, hemoglobin blood oxygen saturation, blood gases, lactate or any other blood parameter.

Blood monitoring system

The present invention is a programmable, automated device for measurement and analysis of blood analytes and blood parameters. The device components are preferably combined in a single housing and either programmed to initiate automatic, periodic blood sampling or initiate automatic blood sampling via operator input or in response to a predefined event or in response to a signal from another instrument. The device operates automatically to draw blood samples and analyze the drawn blood samples to obtain the desired blood readings.

Wearable, programmable automated blood testing system

A device and method for noninvasively quantifying important physiological parameters in blood. The device and method utilizes changes in molecular behavior induced by thermal energy of change to facilitate the measurement of the physiological parameters in blood. Oxygen saturation, partial pressure of oxygen, partial pressure of carbon dioxide, concentration of bicarbonate ion and total carbon dioxide, acid-base balance, base excess, hemoglobin level, hematocrit, oxyhemoglobin level, deoxyhemoglobin level, and oxygen content can all be determined quickly, easily, and continuously. There is no need for skin puncture or laboratory analysis.

Device and method for noninvasive continuous determination of blood gases, pH, hemoglobin level, and oxygen content

In vitro and in vivo animal studies have shown accurate measurements of arterial blood pH (pHa), carbon dioxide tension (PaCO2), and oxygen tension (PaO2) with small intravascular fluorescent probes. Initial human clinical studies showed unexplained intermittent large drops in sensor oxygen tension (PiO2). Normal volunteers were studied to elucidate this problem. In the first part of this study, the probe and cannula were manipulated and the probe configuration and its position within the cannula were varied. The decreases in PiO2 were judged to be primarily due to the sensor touching the arterial wall. Retraction of the sensor tip within the cannula eliminated the problem. In the second part of this study, the accuracy of the retracted probe was evaluated in 4 subjects who breathed varying fractions of inspired oxygen and carbon dioxide. The arterial ranges achieved were 7.20 to 7.59 for pH, 22 to 70 mm Hg for PaCO2, and 46 to 633 mm Hg for PaO2. Linear regression of 48 paired sensor (i) versus arterial values showed pHi = 0.896 pHa + 0.773 (r = 0.98, SEE = 0.017); PiCO2 = 1.05 PaCO2-1.33 (r = 0.98, SEE = 2.4 mm Hg); and PiO2 = 1.09 PaO2-20.6 (r = 0.99, SEE = 21.2 mm Hg). Bias (defined as the mean differences between sensor and arterial values) and precision (SD of differences) were, respectively, -0.003 and 0.02 tor pHi, 0.77 and 2.44 mm Hg for PiCO2, and -2.9 and 25.4 mm Hg for PiO2. The mean in vivo 90% response times for step changes in inspired gas were 2.64, 3.88, and 2.60 minutes, respectively, for pHi, PiCO2, and PiO2.

/pdf/progress-in-the-development-of-a-fluorescent-intravascular-45knmy0wse.pdf

Progress in the development of a fluorescent intravascular blood gas system in man

A method for making a sensing element, and an assembled sensing element, useful in sensing the concentration of a gas, e.g., carbon dioxide, in a medium, e. g. blood, are disclosed. In one embodiment, the method comprises placing a quantity of a sensing composition precursor between and in contact with a transparent, gas impermeable solid disc and an opaque, gas permeable film, the sensing composition precursor comprises a sensing component, a polymer precursor and a cross-linking agent; and forming a gas sensing composition from this quantity of sensing composition precursor.

Method for making gas sensing element

A sensor cassette for use in measuring a compositional parameter of blood comprising a housing having a wall defining a passage which is adapted to receive blood. The wall is at least somewhat permeable to the compositional parameter. A support element, which is less permeable to the compositional parameter of blood than the housing, is carried by a region of the wall. A sensor is carried by the support element and provides a signal in response to the compositional parameter. The support element separates the sensor from at least a portion of such region of the wall so that the affect of the permeability of the housing to the compositional parameter on the signal from the sensor is reduced.

Apparatus and method for use in measuring a compositional parameter of blood

A method for making a sensing element, and an assembled sensing element (20), useful in sensing the concentration of a gas, e.g., carbon dioxide, in a medium, e.g. blood, are disclosed. In one embodiment, the method comprises placing a quantity of a sensing composition precursor (22) between and in contact with a transparent, gas impermeable solid disc (14) and an opaque, gas permeable film (21), the sensing composition precursor comprises a sensing component, a polymer precursor and a cross-linking agent; and forming a gas sensing composition from this quantity of sensing composition precursor.

Method for making a gas sensing element

Sensing composition precursors and sensing compositions, useful in sensing the concentration of a gas, e.g., carbon dioxide, in a medium, e.g., blood, are disclosed. In one embodiment, the sensing composition precursor comprises a dispersed aqueous liquid including a sensing component dissolved therein, a polymer precursor, and a hydrophilic dispersing agent selected from hydroxyalkyl celluloses and mixtures thereof in an amount effective to facilitate maintaining the dispersed aqueous liquid.

Thomas P. Maxwell

Papers

Progress in the development of a fluorescent intravascular blood gas system in man

Method for making gas sensing element

Apparatus and method for use in measuring a compositional parameter of blood

Method for making a gas sensing element

Gas sensing element and method for making same