How can I compute blood gases?

Answer 1

Medical Blood gases (like oxygen and carbon dioxide) are usually not computed, they are measured with an instrument called a blood gas analyzer.

A blood specimen is injected and then chemical electrodes measure the appropriate substances and calculate the answers in standard units.

The pH of the blood is usually measured at the same time. Carrbon monoxide can be measured by this technique also.

A slightly different protocol is required for the specimen collection depending upon whether the sample is arterial or venous blood. The specimen is usually kept on ice until analyzed.

Answer 2

Blood gases are drawn from an artery with a small needle attached to a syringe. The syringe contains a small amount of heparin to prevent clotting of the blood. If possible, the sample is obtained from the radial artery at the wrist. When repeated samples are necessary, an “arterial line” (a small catheter left inside the artery) is used. In newborns, the samples would be obtained through an umbilical artery catheter. When the radial pulse is unobtainable (blood pressure less than 60 systolic) the sample is usually obtained from the femoral artery in the groin.
Prompt flow of blood into the syringe (without pulling back on the plunger) shows that the sample is truly from the artery. However, during CPR the sample must often be aspirated from the femoral artery.
The sample is corked off immediately to prevent exposure to room air, and placed in ice. The site of the arterial puncture is kept under pressure (to prevent hematoma formation) for about ten minutes.
The sample is placed in a machine that measures the pH, partial pressure of oxygen (PaO2), and carbon dioxide (PaCO2). Usually the hemoglobin is measured in a separate machine. These are the “measured values,” from which other values are calculated. “Controls" (solutions of known pH) are used to insure the accuracy of the measurements.
Readings may need to be adjusted for the patient’s temperature. Oxygen, carbon dioxide, and pH are all affected by a change in patient temperature. The machine is calibrated for measurements on a patient with a temperature of 37.0 centigrade. Measurements must be adjusted for temperature because:
1) Increased temperature changes the volume of the dissolved gas (not CO2 that has been converted to HCO3-) in the serum and red blood cells. The ideal gas equasion shows that volume of a gas (V) and temperature (T) are directly proportional.

Answer 3

I dunno...