Final answer:
To provide the highest concentration of oxygen to a client with fluctuating pulse oximeter readings, the nurse should use a nonrebreather mask. It delivers over 90% oxygen and is the most efficient among the options provided.
Step-by-step explanation:
A nurse is caring for a client who has viral pneumonia and is experiencing low pulse oximeter readings between 79% and 88%. To provide the highest concentration of oxygen, the nurse should initiate a nonrebreather mask. This mask is designed to allow the patient to inhale maximum oxygen while exhaling carbon dioxide without rebreathing it. As the partial pressure of oxygen in alveolar air is around 104 mm Hg, effective oxygen therapy is necessary to ensure sufficient oxygenation when ventilation is compromised, as in the case of pneumonia.
A nonrebreather mask is best suited for this purpose as it has a reservoir bag attached to the mask, allowing the delivery of a high concentration of oxygen. It is capable of providing the patient with over 90% oxygen. In contrast, options B, C, and D, such as the Venturi mask, simple face mask, and partial rebreather mask, deliver lower concentrations of oxygen.