For which of the following patients is supplemental oxygen most critical?

Supplemental oxygen is most critical for patients with suspected pneumonia due to the way pneumonia affects the respiratory system. Pneumonia can lead to decreased oxygen exchange in the lungs because the alveoli become inflamed and filled with fluid or pus, significantly impairing their ability to transfer oxygen into the bloodstream. This can result in hypoxia, where the body tissues do not receive enough oxygen to function properly. Therefore, providing supplemental oxygen helps improve oxygen saturation levels, ensuring that vital organs receive adequate oxygen while the body is fighting the infection.

In contrast, patients with a common cold may experience mild respiratory symptoms but typically do not have significant issues with oxygenation. Those with stable angina experience chest pain due to temporary reductions in blood flow to the heart muscle, rather than direct respiratory problems requiring supplemental oxygen. Similarly, patients with mild allergies might have some respiratory discomfort, but this usually does not necessitate oxygen therapy unless there are complications like severe asthma exacerbation or anaphylaxis, which are not indicated in the given choice.