What is the value of pO₂ (in deoxygenated blood) minus pCO₂ (in deoxygenated blood)?

The partial pressure of oxygen (pO₂) and carbon dioxide (pCO₂) in deoxygenated blood are critical parameters in understanding respiratory physiology. Deoxygenated blood, which is transported from the tissues back to the lungs, contains lower levels of oxygen and higher levels of carbon dioxide compared to oxygenated blood.

For deoxygenated blood:

• pO₂: The partial pressure of oxygen in deoxygenated blood is approximately 40 mm Hg.
• pCO₂: The partial pressure of carbon dioxide in deoxygenated blood is around 45 mm Hg.

To find the difference between these values, we calculate:

pO₂ – pCO₂ = 40 mm Hg – 45 mm Hg = -5 mm Hg

This negative result indicates that in deoxygenated blood, the partial pressure of carbon dioxide (pCO₂ in deoxygenated blood) is higher than the partial pressure of oxygen (pO₂). The higher pCO₂ in deoxygenated blood reflects the accumulation of carbon dioxide as a byproduct of cellular respiration, which is then transported back to the lungs for exhalation.

In summary, the difference between the partial pressure of oxygen and the partial pressure of carbon dioxide in deoxygenated blood is -5 mm Hg, highlighting the physiological adaptations for gas exchange. The elevated pCO₂ in deoxygenated blood plays a vital role in maintaining acid-base balance and supporting effective respiration.