Spontaneous variability of the hemoglobin affinity for oxygen

Area of Science:

• Physiology
• Biochemistry

Background:

• P50 determination is crucial for assessing oxygen transport.
• Variability in P50 measurements can impact clinical interpretations.
• Understanding factors influencing P50 is essential for accurate physiological assessment.

Purpose of the Study:

• To evaluate the accuracy and variability of a P50 determination method.
• To investigate potential causes of P50 variation in healthy individuals.
• To compare in vivo P50 variability with changes in stored blood.

Main Methods:

• P50 and 2,3-DPG levels were measured on different days in laboratory staff.
• Oxygen partial pressure (PO2) was fixed by tonometry.
• Oxyhemoglobin saturation was determined using Van Slyke analysis.
• Stored CPD bank blood samples were analyzed over 5-20 days.

Main Results:

• Significant day-to-day variability in P50 was observed in healthy individuals.
• This variability was not correlated with changes in 2,3-diphosphoglycerate (2,3-DPG) or red cell pH.
• Stored blood samples showed expected decreases in P50 and 2,3-DPG over time.

Conclusions:

• P50 measurements in healthy individuals exhibit significant day-to-day variability.
• Factors other than 2,3-DPG and pH likely contribute to in vivo P50 fluctuations.
• Methodological consistency is vital, but biological variability must also be considered in P50 interpretation.