Patients with heart failure and a maximum inspiratory pressure (MIP) <70% of predicted MIP to age, considered as inspiratory muscle weakness. Following the recruitment process, these volunteers will be evaluated by spirometry and manovacuometry. Afterwards, volunteers will be also assessed in a maximal exercise ramp test. Before and after the ramp test, the optoelectronic pletysmography will be performed to analyse the chest wall tricompartmental distribution and the shortening velocities of rib cages muscles. Also a high-definition ultrasonography will be performed to measure the right diaphragmatic cupule thickness

Patients with heart failure and do not have a maximum inspiratory pressure (MIP) > 70% of predicted MIP to age, considered as inspiratory muscle weakness. Following the recruitment process, these volunteers will be evaluated by spirometry and manovacuometry. Afterwards, volunteers will be also assessed in a maximal exercise ramp test. Before and after the ramp test, the optoelectronic pletysmography will be performed to analyse the chest wall tricompartmental distribution and the shortening velocities of rib cages muscles. Also a high-definition ultrasonography will be performed to measure the right diaphragmatic cupule thickness

The maximal exercise ramp test, symptom-limited, performed by all patients in the study was performed based on treadmill ramp protocol through ErgoPC Elite® software associated with 12-channels electrocardiogram. Respiratory variables were obtained in standard conditions of temperature, pressure and humidity (StPD), breath-by-breath, with the patient breathing through a face mask without leaks coupled to gas analyzer (Cortex - Metamax 3B, Germany).To ensure that patients reached maximum effort during the examination, only the tests which patients obtain a respiratory exchange ratio (RR) ≥1.1 were accepted .

A high-definition ultrasound in the the B mode with linear transducer of 7.5 megahertz was used to measure diaphragmatic thickness. In the lateral decubitus position, the transducer was positioned perpendicular to the chest, between the eighth and ninth intercostal spaces between the right anterior and medium axillary lines. Diaphragm was identified by two hyperechoic (bright) lines parallel to the pleural and parietal membranes respectively. The measurement of diaphragm thickness was held from the middle of the pleural line to the middle of peritoneal. The average of 3 final measures taken at the apposition zone obtained: at functional residual capacity (thickness of the relaxed diaphragm - Erel) at the end of the total lung capacity (thickness of the diaphragm contracted - Econt) and during a maximal inspiratory pressure maneuver from functional residual capacity.

The images generated by the triangulation of the infra-red light reflected by 89 markers placed over volunteers' chest walls and captured by 8 cameras allows the visualization of the same thoraxes as entire structure and in its own tricompartmental division: pulmonary rib cage (RCp), abdominal rib age (RCab) and abdomen (AB). Each compartment can be evaluated in terms of their volume variation across the recorded respiratory cycle.