What condition may require immediate oxygen therapy in the setting of a third-degree AV block?

In the context of a third-degree AV block, also known as complete heart block, there is a complete dissociation between the atrial and ventricular electrical activity. This condition can lead to significant drops in cardiac output, as the ventricles may beat at an inadequate rate to maintain sufficient perfusion to the body's tissues. As a result, patients may experience compromised oxygen delivery to vital organs, leading to hypoxia.

Immediate oxygen therapy is crucial in this scenario because the oxygen saturation of hemoglobin in the blood may be negatively affected due to inadequate cardiac output, which can result in hypoxia. Improving oxygenation can help mitigate the impact of the low cardiac output on organ function and cellular metabolism.

In contrast, conditions such as acute pulmonary embolism and respiratory failure may also necessitate oxygen therapy, but they are not directly due to the compromised cardiac output seen in a third-degree AV block. Severe hypertension, while it represents a critical condition, does not inherently lead to immediate oxygen requirements and would be managed differently. Thus, hypoxia resulting from compromised cardiac output during a third-degree AV block takes precedence in justifying the need for immediate oxygen therapy in this setting.