**Core Concept**
The patient's presentation is suggestive of a respiratory infection exacerbating his chronic obstructive pulmonary disease (COPD), leading to a multifocal atrial tachycardia (MAT) arrhythmia. MAT is a type of atrial arrhythmia characterized by discrete P waves with at least three different morphologies, often seen in patients with underlying pulmonary disease.

**Why the Correct Answer is Right**
MAT is often associated with severe respiratory disease, such as COPD, and is thought to be caused by the release of inflammatory mediators from the lungs, leading to atrial irritability. The patient's symptoms, including increased shortness of breath, cough, and sputum production, are consistent with a respiratory infection exacerbating his COPD. The multifocal atrial tachycardia is likely a result of the pulmonary disease, and treatment should focus on addressing the underlying cause.

**Why Each Wrong Option is Incorrect**
**Option A:** **Adenosine** is used to treat supraventricular tachycardia (SVT), which is a different type of arrhythmia characterized by a regular rhythm. MAT is a more complex arrhythmia, and adenosine may not be effective in this case.
**Option B:** **Digoxin** is used to treat atrial fibrillation and atrial flutter, but it may actually worsen MAT by increasing atrial irritability.
**Option C:** **Lidocaine** is a class Ib anti-arrhythmic medication that can be used to treat MAT, but it is not the first-line treatment.
**Option D:** **Beta blockers** are not typically used to treat MAT, as they can worsen bronchospasm in patients with COPD.

**Clinical Pearl / High-Yield Fact**
MAT is often seen in patients with severe respiratory disease, including COPD and pneumonia. It is essential to address the underlying cause of the arrhythmia, which is usually the respiratory disease, rather than just treating the arrhythmia itself.

**Correct Answer:** C. Lidocaine is used to treat MAT and can help stabilize the cardiac rhythm in this patient.