Beneficial effects of dietary carbohydrate restriction in chronic cor pulmonale.

To explore the effects of moderate and severe reductions in carbohydrate intake on abnormal pulmonary physiology in chronic hypercapneic respiratory failure, spirometric, metabolic, arterial blood gas tension, and oximetric studies were carried out in eight patients who took, in random order daily for a week, either 50 g or 200 g of carbohydrate in an isocaloric diet. At the end of a week's daily intake of an isocaloric diet containing 200 g of carbohydrate, all patients experienced a subjective improvement; the mean body weight was 55.5 +/- 15.4 kg (1 SD) compared with 56.0 +/- 16.0 kg during the control dietary period, the arterial carbon dioxide tension decreased from a mean of 56.9 +/- 6.7 to 50.9 +/- 6.2 mm Hg (p less than 0.005), and the arterial oxygen tension increased from a mean of 50.6 +/- 7.3 to 62.0 +/- 14.5 mm Hg (p less than 0.02). After a week's intake of 50 g of carbohydrate in an isocaloric diet, the body weight and arterial oxygen tension did not change significantly, but the arterial carbon dioxide tension decreased still further to 48.0 +/- 7.8 mm Hg (p less than 0.05). Mouth pressure at 100 msec after the start of inspiration, as a measure of respiratory center output, was significantly higher during both the low carbohydrate intakes compared with the control dietary period. The spirometric data, ventilation-perfusion distribution measurements, oxygen consumption, and carbon dioxide production did not change significantly during various dietary periods. It is concluded that, under these short-term, hospital-controlled conditions, a reduction in the carbohydrate intake to 200 g a day improves the general well-being of patients with chronic hypercapneic respiratory failure, increases arterial oxygen tension, and decreases arterial carbon dioxide tension. A further reduction in the carbohydrate intake to 50 g a day provides further beneficial effects, and such a diet may be used in patients with intractable respiratory failure.