What will be hemoglobin saturation, if P02 is 60 mm Hg at pH 7.4 and temperature 37degC ?
**Core Concept**
Hemoglobin saturation is the proportion of hemoglobin molecules that are bound to oxygen, and it is influenced by the partial pressure of oxygen (PO2), pH, and temperature. The hemoglobin-oxygen dissociation curve describes the relationship between PO2 and hemoglobin saturation.
**Why the Correct Answer is Right**
At a PO2 of 60 mmHg, pH 7.4, and temperature 37°C, the hemoglobin-oxygen dissociation curve is shifted to the right, indicating that the hemoglobin is more readily releasing oxygen to the tissues. This is due to the Bohr effect, where a decrease in pH (increase in acidity) reduces the affinity of hemoglobin for oxygen. As a result, the hemoglobin saturation is lower than at higher PO2 levels. The exact value can be calculated using the Hill equation or a hemoglobin-oxygen dissociation curve calculator.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it would require a much higher PO2 to achieve the same level of hemoglobin saturation, which is not physiologically plausible.
**Option B:** This option is incorrect because it would imply that hemoglobin saturation is independent of PO2, which is not true according to the hemoglobin-oxygen dissociation curve.
**Option C:** This option is incorrect because it would suggest that hemoglobin saturation is higher at a lower PO2, which is the opposite of what is observed on the hemoglobin-oxygen dissociation curve.
**Clinical Pearl / High-Yield Fact**
The Bohr effect is a critical concept in understanding how changes in pH and PO2 affect hemoglobin saturation. It is essential to remember that a decrease in pH (increase in acidity) shifts the hemoglobin-oxygen dissociation curve to the right, making it easier for hemoglobin to release oxygen to the tissues.
**Correct Answer:** **C. 70-80%**