A 45-year-old male presents to the emergency department with shortness of breath and fatigue. He has a history of chronic obstructive pulmonary disease (COPD). His arterial blood gas analysis shows a partial pressure of carbon dioxide (PaCO2) of 60 mmHg (normal: 35-45 mmHg) and a pH of 7.30 (normal: 7.35-7.45), indicating respiratory acidosis. In the context of this patient, what is the primary form in which carbon dioxide (CO2) is transported in the blood from the tissues to the lungs?
