PROBES AND SENSORS FOR ASCERTAINING BLOOD CHARACTERISTICS AND METHODS AND DEVICES FOR USE THEREWITH

1 . A probe for use in a patient having a vessel carrying blood to ascertain characteristics of the blood, the probe comprising:

a cannula adapted to be inserted into a vessel of a patient and having a proximal extremity and a distal extremity, the cannula having a length so that when the distal extremity is in the vessel of the patient the proximal extremity is accessible outside of the patient;

a gas sensor assembly carried within the distal extremity of the cannula for determining gas characteristics of the blood in the vessel;

a pH sensor assembly carried within the distal extremity of the cannula for determining pH of the blood in the vessel; and

a pressure sensor assembly carried within the distal extremity of the cannula for determining pressure of the blood in the vessel.

2 . The probe of claim 1 , wherein the pressure sensor assembly comprises a solid state pressure sensor.

3 . The probe of claim 1 , wherein the distal extremity of the cannula comprises a gas permeable material proximate to the gas sensor assembly.

4 . The probe of claim 1 , further comprising an electrolyte solution disposed within the cannula, and wherein the gas sensor assembly includes electrodes disposed in the electrolyte solution for providing electrical inputs to and electrical outputs from the gas sensor assembly.

5 . The probe of claim 1 , wherein the gas sensor assembly comprises an oxygen sensor assembly.

6 . The probe of claim 5 , wherein the gas sensor assembly further comprises a carbon dioxide sensor assembly.

7 . The probe of claim 6 , further comprising conductor elements connected to the oxygen sensor assembly and to the carbon dioxide sensor assembly and configured to supply electrical outputs to the proximal extremity of the cannula.

8 . The probe of claim 5 , wherein the oxygen sensor assembly includes:

an electrolyte fill solution disposed in the cannula; and

first, second, and third electrodes disposed in the electrolyte fill solution and configured to provide electrical outputs to the proximal extremity of the cannula.

9 . The probe of claim 1 , further comprising a flex circuit assembly extending from the proximal extremity of the cannula to the distal extremity of the cannula, wherein the gas sensor assembly, the pH sensor, and the pressure sensor assembly are mounted on the flex circuit assembly.

10 . The probe of claim 1 , wherein the gas sensor assembly, the pH sensor assembly, and the pressure sensor assembly are attached to conductor elements of a flex circuit assembly that provides a zero profile connector.

11 . The probe of claim 2 , combined with a module comprising electronics configured to create and digitize analog signals from the pressure sensor assembly and software algorithms configured to provide measurements of systolic and diastolic blood pressure, mean arterial pressure, heart rate, and systemic vascular resistance.

12 . The probe of claim 5 , wherein the oxygen sensor assembly comprises a working electrode, a counter electrode, and a reference electrode, and wherein the oxygen sensor assembly has a structure that supports high electrochemical activity between the working electrode and the counter electrode and that inhibits electrochemical activity between the working electrode and the reference electrode.

13 . The probe of claim 12 , wherein a voltage of each of the working electrode, the counter electrode, and the reference electrode is set relative to the others of the working electrode, the counter electrode, and the reference electrode in order to optimize performance of the oxygen sensor assembly.

14 . The reference electrodes probe of claim 12 , wherein the reference electrode comprises a AgCl coating on a bare Ag wire.

15 . The probe of claim 1 , wherein the pressure sensor assembly comprises a pressure sensing element and a pressure sensor chamber that is not perfectly round after the cannula has been pre-treated, due to an internal structure near the pressure sensing element, or both.