Inspiratory muscle training in chronic airflow limitation: comparison of two different training loads with a threshold device

Skeletal muscle abnormalities in patients with COPD: contribution to exercise intolerance

Exercise intolerance in COPD patients appears to be in part because of skeletal muscle dysfunction. Studies using biopsy techniques and magnetic resonance spectroscopy have demonstrated changes in enzyme activities and metabolism that indicate reduced oxidative capacity in the peripheral muscles of these patients. Regarding the respiratory muscles, the biochemical characteristics have been studied in only a few works and the results seem to depend on the specific muscle group studied. Several factors, such as hypoxemia, nutritional status, pharmacological treatment, and deconditioning, may be responsible for these skeletal muscle abnormalities. This brief review describes the changes in peripheral and respiratory muscles in COPD patients based on data from the literature. The causes of these muscle abnormalities, their contribution to exercise intolerance, and the effects of training are then discussed. We conclude with suggested directions for future investigation using contemporary noninvasive technologies.

General exercise training improves ventilatory and peripheral muscle strength and endurance in chronic airflow limitation

We studied the impact of a 6-wk supervised, multimodality endurance exercise training program (EXT) on strength and endurance of ventilatory and peripheral muscles in patients with chronic airflow limitation (CAL), and determined whether potential improvements contributed to relief of exertional breathlessness (B) and perceived leg effort/discomfort (LE), respectively. Twenty breathless patients with stable CAL (FEV1 = 41 +/- 3% predicted; mean +/- SEM) were tested at 6-wk intervals at baseline, after a nonintervention control period (pre-EXT), and post-EXT. Measurements included: pulmonary function tests (PFTs), maximal inspiratory/expiratory pressures (MIP, MEP), inspiratory muscle endurance (V(LIM)), quadriceps strength and endurance, exercise endurance, and submaximal cycle exercise with cardioventilatory and symptom responses. Measurements at baseline and pre-EXT were identical. Post-EXT, PFTs did not change; exercise endurance measured on the treadmill, cycle ergometer, arm ergometer, and by 6-min walk distance increased 40 +/- 8%, 43 +/- 10%, 12 +/- 5%, and 34 +/- 9%, respectively (p < 0.05); quadriceps strength increased 21 +/- 5% (p < 0.01); MIP and MEP increased 29 +/- 11% and 27 +/- 11%, respectively (p < 0.05); V(LIM) increased almost threefold (p < 0.05). At isotime near end-exercise, B, LE, carbon dioxide production (VCO2), oxygen consumption (VO2), ventilation, and breathing frequency (F) all fell after EXT (p < 0.05): deltaB correlated with deltaF (r = 0.58, p < 0.01). Increased MIP and V(LIM) did not correlate with improved breathlessness or exercise endurance. Similarly, changes in quadriceps strength and endurance did not correlate with changes in LE or exercise endurance. In conclusion, general nonspecific EXT improved ventilatory and peripheral muscle function in severe CAL, but such improvements did not appear to contribute significantly to reduced exertional symptoms and enhanced exercise performance.

Pulmonary rehabilitation for patients with advanced lung disease

Pulmonary rehabilitation has gradually become a cornerstone of treatment for patients with advanced lung disease. Although most of the data that has resulted in the acceptance of this therapeutic modality has been obtained from studies of patients with chronic obstructive pulmonary disease, the basic principles and tools are applicable to patients with many other limiting chronic diseases of the respiratory system. Because new therapeutic strategies, such as lung volume reduction surgery and lung transplantation, require well-conditioned patients, pulmonary rehabilitation is becoming a crucial component of the overall treatment strategy of many patients who heretofore were deemed untreatable. This article reviews the basic definitions, objectives, components, and outcomes of pulmonary rehabilitation in order to provide the reader with a practical and inclusive overview of the topic.

Arm training reduces the VO2 and VE cost of unsupported arm exercise and elevation in chronic obstructive pulmonary disease

BACKGROUND

Patients with severe chronic obstructive pulmonary disease (COPD) may develop dyspnea with minimal arm activity, thoracoabdominal dyssynchrony with unsupported arm exercise (UAEX) and increased oxygen uptake (VO2), and minute ventilation (VE) with simple unsupported arm elevation (UAE) and UAEX. We investigated whether unsupported arm training, as the only form of exercise, could decrease the VO2 and VE cost (percentage increase from resting baseline) associated with unsupported arm elevation and exercise, respectively.

METHODS

Twenty-six patients with severe COPD were randomized to 21-24 sessions of unsupported arm (ARMT) or low-intensity resistive breathing (RBT) training as the only form of exercise. Patients were studied before and after training using a metabolic cart and esophageal and gastric pressures to evaluate metabolic and respiratory muscle function.

RESULTS

After ARMT, the VO2 (58% vs 38% increase, P < 0.05) and VE (41% v. 21% increase, P < 0.05) cost for UAEX at exercise isotime decreased and endurance time increased. Similarly the VO2 (25% vs 18% increase, P < 0.05) cost decreased and VE no longer increased in response to 2 minutes of UAE after ARMT. The RBT group showed no such change. No improvement in ventilatory load or respiratory muscle function could be identified to explain the physiologic changes observed. After ARMT, mean inspiratory flow (VT/TL), a measure of central respiratory drive, was reduced during UAEX and the expected increase during UAE did not occur.

CONCLUSION

We conclude that arm training reduces the VO2 and VE cost of UAE and UAEX, possibly through improved synchronization and coordination of accessory muscle action during unsupported arm activity.

Reliability of a commercially available threshold loading device in healthy subjects and in patients with chronic obstructive pulmonary disease

BACKGROUND

Threshold loading with the Nickerson and Keens' device is frequently applied in the training and assessment of inspiratory muscles. However, this equipment is not easily applied in clinical practice and training. A study was therefore designed to investigate the accuracy and reliability of the Threshold, a commercially available threshold loading device.

METHODS

The resolution (accuracy) of the system was determined by measuring variation of pressure and flow during one minute in an experimental setup. The reproducibility and flow independence were then determined during threshold loading at six different inspiratory loads between 25% and 50% maximal inspiratory pressure (PImax) in 10 patients with chronic obstructive pulmonary disease (COPD) and eight healthy subjects.

RESULTS

In the first experiment the mean variation of the sustained pressure for all loads was 1.7%. The mean coefficients of variation for pressure and flow measurements were 0.2% and 3%, respectively. In the second experiment the healthy subjects showed mean coefficients of variation for pressure and flow of 0.8% and 20.5%, respectively, and the patients showed mean coefficients of variation of 0.6% and 14.5%, respectively.

CONCLUSIONS

During the in vitro experiment as well as during the experiments in patients with COPD and in healthy subjects only small variations in pressure were observed despite large variations in flow. The Threshold is a reliable and reproducible device for loading inspiratory muscles in patients with COPD as well as in healthy subjects.