BREATHING PATTERN, VENTILATORY DRIVE AND RESPIRATORY MUSCLE STRENGTH IN PATIENTS WITH CHRONIC HEART-FAILURE

The purpose of this study was to evaluate whether chronic heart failure (CHF) may induce changes in breathing pattern and ventilatory neural drive. We studied 45 male inpatients with CHF, (25 patients in NYHA class II, 20 in class III) and 22 sex-matched post myocardial infarction patients without left ventricular dysfunction who served as controls. CHF patients underwent right heart catheterization and assessment of cardiac output by thermodilution technique. Patients and controls underwent evaluation of left ventricular ejection fraction by 2D echocardiography, spirometry, diffusion capacity, blood gases, breathing pattern, mouth occlusion pressure and respi ratory muscle strength determination. Results of CHF patients were compared to controls and evaluated for differences according to the degree in severity of functional impairment. CHF patients showed a slight reduction in lung volumes and in diffusion capacity. In CHF neural drive, as assessed by mouth occlusion pressure (P-0.1), was significantly increased in comparison to controls (P-0.1 = 1.86 (0.7) and 1.4 (0.6) cmH(2)O in CHF and controls respectively). Analysis of breathing pattern showed only a slight yet significant nifiicant increase in respiratory frequency while respiratory muscle strength, as assessed by measurement of maximal inspiratory and expiratory pressures (MIP and MEP respectively) was slightly reduced MIP-79(27) and 104(28); MEP=111(32) and 142(33) cmH(2)O respectively). Observed changes were more relevant in patients with advanced NYHA functional classes whereas no relationship among indices of cardiac and respiratory function was found. We conclude that chronic heart failure induces changes in neural ventilatory drive and respiratory muscle strength related to the severity of the disease.