Neonatal Nurse Practitioner Practice Exam

What does a left shift in hemoglobin affinity indicate about oxygen delivery?

1. Oxygen is easily released to the tissues

2. Oxygen is prevented from reaching the tissues

3. Oxygen bonds more loosely in circulation

4. Oxygen is fully saturated in hemoglobin

The correct answer is: Oxygen is prevented from reaching the tissues

A left shift in hemoglobin affinity for oxygen refers to an increase in hemoglobin's affinity, meaning that hemoglobin binds oxygen more tightly. When hemoglobin has a higher affinity for oxygen, it becomes more difficult for oxygen to be released to the tissues. This scenario is typical in conditions such as increased pH (alkalosis) or a decrease in temperature, which promote hemoglobin binding to oxygen more strongly. Understanding this physiological response is crucial for neonatal practitioners. A leftward shift limits the availability of oxygen to the tissues, as hemoglobin holds onto oxygen instead of delivering it where it is needed most. Consequently, this can lead to tissue hypoxia even when oxygen levels in the blood appear normal, as oxygen is 'trapped' by the hemoglobin. In contrast, various factors such as increased carbon dioxide (PCO2), increased temperature, or decreased pH (acidosis) would result in a right shift. A right shift indicates a decreased affinity of hemoglobin for oxygen, facilitating easier release of oxygen to the tissues, thus enhancing oxygen delivery where it is crucial for cellular metabolism.