Pulmonary Vascular Responsiveness at Rest and during Exercise in Idiopathic Pulmonary Fibrosis: Effects of Oxygen and Nifedipine

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Abstract
To detect whether pulmonary vascular responsiveness is a factor which can aggravate the pulmonary hypertension induced by irreversible pulmonary fibrosis, we examined the acute hemodynamic effects of low-flow oxygen and of nifedipine both at rest and during exercise in 8 patients with idiopathic pulmonary fibrosis (IPF). During exercise, the increments in pulmonary artery pressure, pulmonary vascular resistance (PVR), and right ventricular stroke work index relative to resting values were blunted by both treatments. During exercise, both systemic vascular resistance and PVR decreased more significantly after nifedipine than on oxygen (p < 0.001). At exercise, nifedipine administration induced a greater increment in oxygen delivery (CaO2 × CI) than that produced by oxygen breathing (p < 0.01). Our results in patients with IPF seem to confirm that active vasoconstriction of pulmonary vessels may contribute to the pulmonary hypertension during exercise. The evaluation of reversibility of pulmonary hypertension by nifedipine in IPF deserves further long-term studies