Objective: To describe the clinical, subclinical characteristics and their correlation with arterial blood gas (ABG) in patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) treated at Thanh Thuy District Medical Center, Phu Tho Province. Methods: A cross-sectional descriptive study was conducted on 85 inpatients diagnosed with acute exacerbation of COPD from June 2024 to June 2025. Clinical characteristics, GOLD 2023 classification, Anthonisen severity, and ABG analysis at admission were collected. Results: The study subjects had a mean age of 73.4 ± 11.2 years, with males accounting for 94.1%. The prevalence of underweight (BMI < 18.5) was 51.8%. The main clinical symptoms were dyspnea (98.8%), tachypnea (90.6%), and wheezing/rhonchi (82.4%). Most patients were in Group B (49.4%) and had moderate exacerbations (42.5%). Regarding blood gas, 55.3% of patients had hypercapnia (PaCO₂ > 45 mmHg), and 34.1% had acidemia (pH < 7.35). Type 2 respiratory failure was predominant (89.4%), and respiratory acidosis was the most common disorder (29.4%). Reduced pH and elevated PaCO₂ were highly significantly associated with the severity of the exacerbation (p < 0.001). Conclusion: Patients with acute exacerbation of COPD in the study area were predominantly characterized by Type 2 (hypercapnic) respiratory failure. Acidemia (reduced pH) and hypercapnia (elevated PaCO₂) are objective indicators strongly correlated with the clinical severity of the exacerbation (p < 0.001).