This is particularly evident during ILB, that is, a situation requiring a significant rise in inspiratory muscle pressure (Meyer et al., 2001). It is important to note that decreased lower rib cage displacement in CHF patients is not associated to reduced overall chest wall volume variations. This suggests Bortezomib the presence of compensatory mechanisms in the upper rib cage and abdominal compartments

Aliverti et al. (1997) observed that, during exercise, abdominal and rib cage muscles play a double role of preventing costly rib cage distortions and unloading the diaphragm so that it acts as a flow generator. Furthermore, the rib cage and abdominal muscles assume the task of developing the pressures PCI-32765 order required to move the rib cage and abdomen, respectively. This mechanism could be the base of similar compensatory mechanisms observed in the CHF group. Another original finding in the present study was that in both compartments submitted to the action of the diaphragm, namely the lower rib cage and the abdomen, during ILB displacement of the left side was significantly lower than the right in CHF patients, but not among controls. A possible explanation is that cardiomegaly would limit effective diaphragmatic displacement on the left side, where a heart with increased

volume might represent a mechanical load for the diaphragm, altering its normal return to its relaxed position. This hypothesis is supported by Olson et al. (2006) who studied the relationship between cardiac and pulmonary volume in the thoracic cavity of 44 individuals with CHF compared to healthy individuals via radiographic analysis. These authors observed a strong correlation between heart size and pulmonary volume reduction from for CHF patients. They also suggest that increased cardiac volume and reduced pulmonary volume could contribute to the rapid and shallow breathing frequently observed in this population, particularly during exercise. In another study, the same group (Olson et al.,

2007) evaluated pulmonary function in CHF patients with cardiomegaly and observed lower values of FVC, FEV1, FEV1/FVC, and FEF 25–75%. More recently, Olson and Johnson (2011) studied the influence of cardiomegaly on respiratory disorder during exercise in patients with CHF and showed a strong correlation between cardiac volume in tidal volume changes and respiratory frequency during exercise. A limitation of this study is the absence of an additional group for comparison, composed of patients with cardiomegaly related CHF without inspiratory muscle weakness, enabling effects for each of these variables to be evsluated in separadely. However, our data can be extrapolated for patients with CHF associated with muscle weakness, elements commonly found in patients with CHF functional class II or III (NYHA).