Heart Failure Worsens Muscle Strength in COPD

"Knee flexors and extensors muscles were analysed by an isokinetic dynamometer. Positioning of the subjects (sitting with hips flexed to 75°) was standardized based on the length of the thigh and leg to minimize individual differences. Correction for the effect of gravity on neuromuscular performance was accomplished by incorporating limb mass into the calculation of torque production. Previous warm-up was repeated five time with an angular velocity of 400°/s. All patients randomly performed two maximal isokinetic tests: 6 repetitions at 60°/s and 20 repetitions at 300°/s.~Measurements of torque, work (J), power (W) maximum (peak), and fatigue index were obtained in both tests. In addition, data were analysed at percent of prediction (percent pred) by reference values previously described for the Brazilian population, corrected by muscle mass and peak values."

"All exercise tests were performed on an electronically braked cycle ergometer. Standard metabolic and ventilatory responses were measured breath-by-breath using a calibrated, computer-based system.~The incremental exercise test started with 2-min unloaded cycling and increments of 3-10 Watts per min until exhaustion. The anaerobic threshold was estimated by the ventilatory equivalents and V-slope methods and it was determined in agreement by a cardiologist and pulmonologist. Heart rate was determined using the 12-lead electrocardiogram. Throughout the experiment, the pulse hemoglobin saturation (SpO2) was assessed with a pulse oximeter and the 'shortness of breath' was asked at exercise cessation using the 0-10 Borg category ratio scale. All measurements were expressed as percentage predicted for the Brazilian population."

"The six-minute walk test (6MWT) was in accordance with the American Thoracic Society (ATS). The four-minute step test (4MST) consisted of going up and down a 20-cm high, 40-cm wide and 40-cm long step for 4 minutes.~The investigators measured the heart rate and pulse hemoglobin saturation at rest before each test and every minute of both tests. The investigators assessed dyspnoea and leg fatigue at rest and with the modified Borg scale immediately after finishing the test."

"Spirometry, gas transfer, and static lung volumes were measured in all patients, and airflow was measured using a Pitot-tube based on the American Thoracic Society/European Respiratory Society guidelines. Measurement of maximal inspiratory and expiratory pressures was performed from the residual volume and total lung capacity. Resting blood gases were obtained by samples from the radial artery."

The same medical doctor performed all echocardiograms and all patients underwent comprehensive echocardiography.

"Body composition was assessed using a body composition analyzer. Percent body fat was estimated from the resistance and reactance values.~Resistance values and the subject's height (meters), weight (kg), sex, and age (years) were entered into a computer program to estimate percentage of fat, fat mass (FM), and muscle mass (MM)."