[Hyperventilation and oxygen supply of the myocardium. II. Effect of nitroglycerin and dipyridamole]

1. Voluntary hyperventilation during rest in the recumbent position induces a fall in H+ concentration, PCO2 and PO2 in mixed venous blood and in the blood of the coronary sinus. 2. If the breathing volume is increased during voluntary hyperventilation between 2- and 2.5 fold above the volume at rest, O2 uptake increases by only 6% but CO2 excretion rises by 66%. 3. Cardiac output decreases by 8% and the O2 extraction of the myocard increases by 12%. There is a quantitative relationship between arterial pH or PCO2 and changes in the systemic and coronary circulation. Blood pressure decreases in the pulmonary circulation. 4. Nitroglycerin during hyperventilation produces an additional reduction in cardiac output but no effect on the O2 extractions of the myocard. 5. With dipyridamol, the O2 extraction of the myocard is reduced and the PO2 in the blood of the coronary sinus increases. 6. In the case of severe coronary obstruction, the effect of dipyridamol can cause acute angina pectoris and left heart insufficiency due to poststenotic ischemis (steal syndrome).