Excess carbohydrate calories in total parenteral nutrition (TPN) solutions can precipitate acute hypercapnic respiratory failure in patients with chronic lung disease secondary to increased carbon dioxide (CO2) production. Two young patients recovering from the adult respiratory distress syndrome experienced hypercapnia during weaning as a result of nutritionally related increased CO2 production. As carbohydrate calories were decreased, CO2 production diminished and hypercapnia resolved. Hypercapnia as a complication of nutritional support during weaning can occur in patients without chronic lung disease and is corrected by decreasing carbohydrate calories.