As the struggle continues, the body produces increasing amounts of carbon dioxide (CO2). If the subject cannot expel it effectively, carbon dioxide and metabolic acids can accumulate, lowering blood pH and increasing the risk of sudden cardiac arrest. The combination of increased carbon dioxide production and the greater effort to breathe can overwhelm the body’s ability to maintain normal blood chemistry. The combination of increased carbon dioxide production and the greater effort to breathe can overwhelm the body’s ability to maintain normal blood chemistry. Drugs: Substance use increases the risk of carbon dioxide accumulating in the blood.