Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation and includes chronic bronchitis and emphysema. ECG changes associated with COPD include right atrial and ventricular enlargement, p pulmonale, and low voltage QRS complexes, often reflecting chronic strain on the right heart due to hypoxic pulmonary vasoconstriction. The document discusses specific ECG findings, criteria for diagnosing COPD, and various patient ECG examples demonstrating these features.