Chest
Volume 106, Issue 4, October 1994, Pages 1007-1013
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Clinical Investigations: Cardiology
A Characteristic Change in Ventilation Mode During Exertional Dyspnea in Patients With Chronic Heart Failure

https://doi.org/10.1378/chest.106.4.1007Get rights and content

Although exertional dyspnea is an important symptom limiting daily lives in patients with chronic heart failure, there is no objective assessment of this symptom. To characterize the exertional dyspnea, ventilatory responses to exercise were studied in relation to exertional dyspnea. 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 assessed from the tidal volume-ventilation rate (Vt-f) relationship. The exercise was performed again after sublingual administration of 5 mg of isosorbide dinitrate. In normal subjects, the f and Vt increased almost 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 from an inadequate increase in Vt and a further increase in f. In 8 of these 17 patients, isosorbide dinitrate improved exertional dyspnea with normalization of the Vt-f relationship; however, in 9 patients whose dyspnea was not improved, the abnormal Vt-f relationship was unaltered. 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 shallow ventilation. The Vt-f relationship appears to be a simple and useful objective assessment of exertional dyspnea in patients with chronic heart failure.

Section snippets

Subjects

We studied 43 ambulatory patients with left ventricular dysfunction and symptoms of mild-to-moderate heart failure, ie, fatigue or dyspnea on effort, as a heart failure group (Table 1). There were 37 men and 6 women, ranging in age from 22 to 79 years (53±2 years, mean±SEM). Thirty patients were classified in New York Heart Association functional class II and 13 were in class III. The cause of heart failure was dilated cardiomyopathy in 27 patients, ischemic cardiomyopathy without angina

Subjective Complaint of Exertional Dyspnea

Among 43 patients in the heart failure group, 20 patients complained of exertional dyspnea at a submaximal exercise level, although they could continue exercise until exhaustion. Exertional dyspnea developed rather abruptly and hence, its onset could be identified in these patients. According to the presence or absence of exertional dyspnea, the heart failure group was divided into two subgroups: group A consisted of 20 patients with exertional dyspnea, and group B included the remaining 23

Discussion

The present study demonstrates that exertional dyspnea in patients with chronic heart failure is characterized by a simultaneous change in the ventilation mode as reflected by an abrupt change in the Vt-f relationship indicating the appearance of rapid and shallow ventilation. Standard gas exchange measurements, including ventilatory equivalent for carbon dioxide, were unable to provide an objective measure of exertional dyspnea. Several investigators have already demonstrated rapid and shallow

ACKNOWLEDGMENT

We are grateful to Dr. Michitoshi Inoue, professor of the Faculty of Medical Information Science of Osaka University School of Medicine, for his helpful comments and criticisms in preparing this manuscript.

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