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 failur e (CHF) may induce changes in breathing pattern and ventilatory neural drive. We studied 45 male inpatients with CHF, (25 patients in NYHA c lass II, 20 in class III) and 22 sex-matched post myocardial infarctio n 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 und erwent evaluation of left ventricular ejection fraction by 2D echocard iography, spirometry, diffusion capacity, blood gases, breathing patte rn, mouth occlusion pressure and respi ratory muscle strength determin ation. Results of CHF patients were compared to controls and evaluated for differences according to the degree in severity of functional imp airment. CHF patients showed a slight reduction in lung volumes and in diffusion capacity. In CHF neural drive, as assessed by mouth occlusi on pressure (P-0.1), was significantly increased in comparison to cont rols (P-0.1 = 1.86 (0.7) and 1.4 (0.6) cmH(2)O in CHF and controls res pectively). Analysis of breathing pattern showed only a slight yet sig nificant nifiicant increase in respiratory frequency while respiratory muscle strength, as assessed by measurement of maximal inspiratory an d 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 f unctional classes whereas no relationship among indices of cardiac and respiratory function was found. We conclude that chronic heart failur e induces changes in neural ventilatory drive and respiratory muscle s trength related to the severity of the disease.