Diaphragmatic function in patients with chronic left ventricular failure.

The aim of this paper is to evaluate the function of respiratory muscles in-patients with chronic moderate left ventricular failure (LVF), and its contribution to the pathophysiology of dyspnea and fatigue. We have studied 20 male patients with LVF, classes II and III of New York Heart Association (NYHA), mean age 66.9+/-10 years (GI) and 19 male aged-matched controls without cardiopulmonary disease mean age 64.6+/-8.4 years (GII). The evaluation included (a) methods derived from volitional manoeuvres, maximal inspiratory pressures at Functional Residual Capacity; maximal expiratory pressures at total lung capacity (TLC); nasal sniff; oesophageal sniff and transdiaphragmatic pressures; (b) methods derived from non-volitional manoeuvres, using bilateral cervical magnetic stimulation of the phrenic nerves, measuring the following twitch pressures (oesophageal, gastric and the transdiaphragmatic). With volitional manoeuvres we have not found statistically significant differences between the two groups: maximal expiratory pressures (cmH(2)O), GI 138+/-42; GII 152+/-40; P=NS and maximal inspiratory pressures (cmH(2)O), GI 74.1+/-22; GII 85+/-16; P=NS. However, these values were significantly lower than those obtained with sniff manoeuvres, nasal sniff (cmH(2)O), GI 95.6+/-22; GII 99.6+/-16; P=NS and oesophageal sniff (cmH(2)O), GI 96.2+/-20; GII 97.5+/-18; P=NS. There were no significant differences between nasal sniff and oesophageal sniff. Using cervical magnetic stimulation, we also didn't find a significant difference for transdiaphragmatic twitch between groups, but the contribution of the diaphragm to the transdiaphragmatic pressure was lower in patients with LVF since the oesophageal twitch was lower (cmH(2)O), GI 11.4+/-3.4; GII 16.3+/-6.8; P<0,004. In conclusion, the contribution of the diaphragm to total ventilation in-patients with moderate LVF is preserved. However, its capacity to generate negative intra-thoracic pressures is decreased since there is a significant decrease in oesophageal twitch. So, it seems that the diaphragm is the first inspiratory muscle to be affected in patients with moderate LVF.