THE EFFECT OF ACETYLCHOLINE UPON RESPIRATORY GAS EXCHANGE IN MITRAL STENOSIS

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Abstract
Infusion of acetylcholine in patients with mitral stenosis breathing 47% O2 caused variable changes in the difference between alveolar and arterial O2 tension (A-a difference) and physiological dead space (VD), both at rest and exercise. A-a difference and VD tended to increase or decrease together, an increase occurring in patients with lower pulmonary arterial pressures while patients with higher pressures showed a decrease. It is suggested that progressive uneveness of distribution of blood flow to the lungs develops in mitral stenosis. As the disease becomes more severe the effects of this predominate over the effects of uneven distribution of ventilation, the adjustments to which account for the observed changes in patients with less severe disease. Pulmonary arterial pressure, heart rate and ventilation during exercise were reduced when breathing 47% O2.