Related Experiment Video
Updated: Oct 20, 2026

Expired CO2 Measurement in Intubated or Spontaneously Breathing Patients from the Emergency Department
Published on: January 29, 2011
Change in PCO2 in red cell suspension following bicarbonate shift
Abstract:
To reveal the CO2 diffusion process into and out of the red blood cell (RBC), changes in PCO, following the HCO3- shift were examined. The RBC suspension was mixed at 37 degrees C with saline solution having different HCO3- concentrations. In proportion to the intracellular HCO3- change caused by the HCO3- shift, the PCO2 change was increased. The rate of change increased as the hematocrit and the initial intracellular HCO3- content decreased. For calculating the above PCO2 change, a theoretical equation was derived from the Henderson-Hasselbalch equation and the relation between both the changes in buffer base and intracellular pH. The calculated PCO2 change coincided well with the measured value, suggesting the validity of the theoretical equations.
Related Concept Videos
Assessment of Diffusion and Perfusion
The Role of Diffusion in Respiration
Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. In the respiratory system, this principle...
Carbon Dioxide Transport in the Blood
Forms of CO2 Transport
1. Dissolved in plasma: A small percentage (7-10%) of CO2 is transported and dissolved directly in the plasma.
2. Carbaminohemoglobin: Just over 20% of CO2 is chemically bound to...
Bicarbonate-Carbonic Acid Buffer
Respiratory Regulation of Acid-Base Balance
When carbon dioxide levels increase in the blood, more H+ and HCO3⁻ are produced, leading to a...
Disorders of Acid-Base Balance
Respiratory Acidosis and Alkalosis
Respiratory acidosis occurs due to an increase in the partial pressure of carbon dioxide PCO2 in the blood. It often arises from shallow breathing or impaired gas exchange caused by...
Diagnosing Acidosis and Alkalosis
First, the pH level is assessed to determine whether the blood pH is normal (7.35–7.45), low (acidosis), or high (alkalosis).
Next, the PCO2 and HCO3− values are examined to...

