02 Measurement & CO2 Absorption

1) It can be chemically reduced (adding electrons) 2) It can serve as an oxidant (taking electrons away) 3) It is paramagnetic (attracted to a magnetic field) 4) is selectively permeable to certain membranes

• polarographic electrode • fuel cell • paramagnetic sensor

to contribute electrons to. A compound that is “reduced” accepts electrons. A “reductant” contributes electrons

Hydrogen Peroxide - will speed up oxidation

4 electrons are consumed

In measuring O2 with the O2 electrode, O2 is consumed. Because oxygen is consumed, current is dependent on diffusion of O2 to the electrode

differs from the pH electrode in that current flows through the circuit when oxygen is present. A small direct polarizing voltage (0.6-0.7 V) is applied across the electrodes.

rate of diffusion

1) large surface area consumed lots of oxygen 2) protein was deposited on the electrode. Solution? Clark’s Electrode!

cover the electrodes with membranes to prevent protein deposition, but allow oxygen in

1) limit the surface area of electrode so less O2 is consumed 2) use voltage pulses to reduce 02 consumption.

Similar to an oxygen battery. It contains a noble metal cathode and a lead (Pb) anode and KOH electrolyte. A semipermeable membrane is exposed to the blood or expired gas.

• too much suction • too much heparin • air in blood

• Syringe crack free with properly fitting plunger • Gases in blood will equilibrate in time with air in polypropylene syringes • High white cell count will increase aerobic respiration and decrease blood oxygen content • Bubbles, if present, will increase oxygen dissolved in blood at lower temperature, such as 4C in ice.

If pt’s temp is different from 37 C, analysis will not be accurate. More gas dissolved in cooler blood than warmer blood. (all measurements corrected for temp of blood)

noninvasive method to measure blood oxygen and carbon dioxide that use the same electrode technology as the CO2 and O2 electrodes.

• airtight seal with skin • heating element to bring skin temp to 43-44C • blood flow to skin increases and capillary O2 and CO2 diffuse to the surface where they are measured by the electrodes

makes use of the fact that oxygen molecules are attracted to a magnetic field (Remember that molecular oxygen has two unpaired electrons). - In one system a stream of gas containing oxygen is put in an oscillating magnetic field. The oscillating magnetic field causes movement of the oxygen molecules. The oxygen movement causes the pressure of the gas to increase as a function of oxygen concentration.

a technology that can be used for measuring oxygen, pH and pCO2.

emission of light or electromagnetic radiation by a substance as the result of absorption of energy of shorter wavelengths. ie: the excitation of a substance by UV light, and emission of visible light.

• to reuse volatile anesthetics in a circuit, CO2 absorption is required • also important in submarines and NASA spacecraft

the end product of metabolism that is kept low in the body by its expiration.

40mmHg arterial 45mmHg venous

4mL/min/kg of body weight