From the Guidelines
Decreased hemoglobin affinity to oxygen at the tissue level is primarily caused by increased body temperature, as evidenced by the Bohr effect, which is supported by the British Thoracic Society guideline for oxygen use in adults in healthcare and emergency settings 1. This phenomenon is known as the Bohr effect, which describes how hemoglobin's oxygen-binding capacity is influenced by various physiological factors. When body temperature increases, it causes a rightward shift in the oxygen-hemoglobin dissociation curve, meaning hemoglobin releases oxygen more readily to tissues. This is physiologically beneficial because tissues with higher metabolic activity generate more heat and require more oxygen. Other factors that decrease hemoglobin's affinity for oxygen include:
- increased carbon dioxide levels (increased pCO2)
- decreased pH (more acidic environment)
- increased levels of 2,3-diphosphoglycerate (2,3-DPG), not decreased as stated in option (b) 1. These factors work together to ensure efficient oxygen delivery to tissues that need it most, particularly during increased metabolic demand. Therefore, the correct answer is (a) increased body temperature, as it is one of the key factors that facilitate the release of oxygen to tissues by decreasing hemoglobin's affinity for oxygen, as described in the guideline 1.
From the Research
Factors Affecting Hemoglobin Affinity to Oxygen
- Decreased hemoglobin affinity to oxygen at the tissue level can be caused by several factors, including:
- Increased 2,3-diphosphoglycerate (2,3-DPG) levels, as it binds to hemoglobin and reduces its oxygen affinity 2, 3
- Increased body temperature, as it increases the kinetic energy of molecules and reduces oxygen affinity 4
- Decreased pH, as it reduces oxygen affinity by increasing the proportion of hemoglobin in the deoxy form 5
- The correct answer is not explicitly stated in the provided studies, but based on the information:
- Decreased 2,3-diphosphoglycerate (option b) would actually increase hemoglobin affinity to oxygen, not decrease it 2, 3
- Decreased pCO2 (option c) and increased pH (option d) would also increase hemoglobin affinity to oxygen, not decrease it 2, 5
- Increased body temperature (option a) is the most likely correct answer, as it would decrease hemoglobin affinity to oxygen 4