blood arterial gases

What information can we get from blood gas analysis?

oxygen saturation, acid-base status

What are the three groups of data from a blood gas report? Which is most important?

1. measured data: pH, pCO2, and pO2

2. calculated data: HCO3 and O2 saturation

3. entered data: temperature, Hgb, FiO2

Most important is measured

How is measured data (pH, pCO2, and pO2) corrected for?

Use the patients temperature

How does CO2 move through the body?

1. as HCO3

2. as carbaminohemoglobin (CO2 + Hgb)

3. as dissolved CO2

what is the acid-base balance equation?

CO2 + H2O = H2CO3 = HCO3 + H

What enzyme is used to convert H2CO3 into HCO3 and H?

carbonic anhydrase

What is the normal pH of blood?

7.4

What is the normal HCO3:H2CO3 ratio?

20:1

If CO2 increases from the lungs, what happens to pH?

decreases

If HCO3 increases from the kidneys, what happens to pH?

increases

What is respiratory acidosis?

when CO2 levels increase acidity, or decrease blood pH

What causes respiratory acidosis?

drug OD, CNS depression, COPD, hypoventilation

What is the henderson-hasselbach equation used to calculate?

plasma pH

What is the henderson-hasselbach equation?

pH = pKa + log(HCO3/pCO2)

What is the pKa for blood?

6.1

How is oxygen transported through the body?

1. dissolved O2

2. oxyhemoglobin (Hgb + O2)

What is oxygen saturation?

the percent of oxygen bound to hemoglobin

What determines the uptake of oxygen by hemoglobin in the lungs?

1. partial pressure of oxygen in alveoli

2. ability of oxygen to diffuse across a membrane

3. affinity of hemoglobin to bind oxygen

What can oxygen saturation determine?

If a patient has hypoxia

What should the oxygen saturation be normally?

>90%

What kind of specimen is required for arterial blood gas analysis?

arterial blood on ice with no exposure to the atmosphere

How do you calculate oxygen saturation?

% = (oxyhemoglobin/oxyhemoglobin + deoxyhemoglobin) * 100