A CHARACTERISTIC CHANGE IN VENTILATION MODE DURING EXERTIONAL DYSPNEAIN PATIENTS WITH CHRONIC HEART-FAILURE

Although exertional dyspnea is an important symptom limiting daily liv es in patients with chronic heart failure, there is no objective asses sment of this symptom. To characterize the exertional dyspnea, ventila tory responses to exercise were studied in relation to exertional dysp nea. Gas exchange data were obtained during a maximal bicycle exercise in 43 patients with chronic heart failure and 20 normal subjects. In addition to standard ventilatory variables, the ventilation mode was a ssessed from the tidal volume-ventilation rate (VT-f) relationship. Th e exercise was performed again after sublingual administration of 5 mg of isosorbide dinitrate. In normal subjects, the f and VT increased a lmost proportionally with exercise intensity. In 17 (85 percent) of 20 patients with exertional dyspnea, the VT-f relationship abruptly lost linearity at the onset of exertional dyspnea. This change resulted fr om an inadequate increase in VT and a further increase in f. In 8 of t hese 17 patients, isosorbide dinitrate improved exertional dyspnea wit h normalization of the VT-f relationship; however, in 9 patients whose dyspnea was not improved, the abnormal VT-f relationship was unaltere d. Only 2 (9 percent) of 23 patients without exertional dyspnea showed the abnormal VT-f relationship. Other ventilatory variables were not different between patients with and without dyspnea. Thus, exertional dyspnea is characterized by simultaneous appearance of rapid and shall ow ventilation. The VT-f relationship appears to be a simple and usefu l objective assessment of exertional dyspnea in patients with chronic heart failure.