Respiratory muscle training: the con argument

The impact of breathing pattern and rate on inspiratory muscles activity

Different rehabilitation programs are used to relieve dyspnea for hyper-inflated lung patients. In this study, a new approach, based on integrated changes in respiratory rate and pattern, for inspiratory muscles rehabilitation and training was examined utilizing noninvasive measurements of the two inspiratory muscles (rib cage inspiratory and neck inspiratory muscles) activity during controlled breathing in healthy subjects. Muscles activity was measured using electromyography, while subjects, breathed at different combinations of respiratory rate (6, 10, 16 breath per minutes) and inspiratory duty cycles (TI/Ttot). The results clearly show that both muscles were most active at the lowest evaluated respiratory rate, and that alteration of the duty cycle at the lowest rate significantly (p< 0.05) changes their electrical activity. Breathing at low respiratory rate RR is recommended for hyper-inflated lung patients in order to improve their gas exchange, therefore, it is recommended for these patients to find their most effective combination of RR and TI/Ttot and to use control breathing to practice their breath at optimum combination.

Respiratory and skeletal muscle strength in chronic obstructive pulmonary disease: impact on exercise capacity and lower extremity function

PURPOSE

We sought to quantify the impact of respiratory muscle and lower extremity strength on exercise capacity and lower extremity function (LEF) in patients with chronic obstructive pulmonary disease (COPD).

METHODS

In 828 persons with COPD, we assessed the impact of reduced respiratory (maximum inspiratory pressure, MIP) and lower extremity muscle strength (quadriceps strength, QS) on exercise capacity (6-minute walk test, 6MWT), and LEF (short physical performance battery). Multiple regression analyses taking into account key covariates, including lung function and smoking, tested the associations between muscle strength and exercise and functional capacity.

RESULTS

For each 0.5 SD decrement in QS, men walked 18.3 m less during 6MWT (95% confidence interval [CI], -24.1 to -12.4); women 25.1 m less (95% CI, -31.1 to -12.4). For each 0.5 SD decrement in MIP, men walked 9.4 m less during 6MWT (95% CI, -15.2 to -3.6); women 8.7 m less (95% CI, -14.1 to -3.4). For each 0.5 SD decrease in QS, men had a 1.32 higher odds (95% CI, 1.11-1.15) of poor LEF; women had a 1.87 higher odds (95% CI, 1.54-2.27). Lower MIP (per 0.5 SD) was associated with increased odds of poor LEF in women (odds ratio = 1.18; 95% CI, 1.00-1.39), but not in men (odds ratio = 1.10; 95% CI, 0.93-1.31).

CONCLUSIONS

In COPD, reduced respiratory and lower extremity muscle strength are associated with decreased exercise and functional capacity. Muscle weakness is likely an important component of impairment and disability in patients with COPD.

Response of the respiratory muscles to rehabilitation in COPD

Respiratory rehabilitation is known to improve outcomes in patients with chronic obstructive pulmonary disease (COPD). The question addressed in the present review is whether these beneficial effects are related to improvements in inspiratory muscle function. Respiratory muscle fatigue often did not occur during exercise in patients with COPD, since exercise limitation usually occurred when significant force reserve in the inspiratory muscles was still present. Notwithstanding, a number of observations may provide indirect evidence that respiratory muscle fatigue may occur during exercise. Some evidence is present that, in normal humans, whole body exercise training improved inspiratory muscle endurance, but no studies are available in patients with COPD. Animal studies invariably demonstrated that exercise training increased the number of oxidative fibers and oxidative enzyme activity in inspiratory muscles. These effects, however, were considerably smaller than the effects found on peripheral muscles with similar fiber composition. Clear evidence indicated that inspiratory muscle training (IMT) improved inspiratory muscle function. Two large meta-analyses indicated that, if the training load was properly controlled, IMT alone or combined with general exercise reconditioning improved inspiratory muscle strength and endurance and dyspnea. The combination did not result in greater improvements in functional exercise capacity. Animal studies and one patient study confirmed the occurrence of structural remodeling of the inspiratory muscles in response to IMT. The final question is whether improvements in inspiratory muscle function produced by IMT lead to improved outcomes in COPD. In all five studies in which training load was adequately controlled, a significant reduction of dyspnea during activities of daily living was found. Eight randomized studies examined the effects of the combination. Greater improvements in exercise capacity were only found in three studies, and none showed a greater reduction in dyspnea.