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      Transdiaphragmatic pressure and neural respiratory drive measured during inspiratory muscle training in stable patients with chronic obstructive pulmonary disease

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          Inspiratory muscle training (IMT) is a rehabilitation therapy for stable patients with COPD. However, its therapeutic effect remains undefined due to the unclear nature of diaphragmatic mobilization during IMT. Diaphragmatic mobilization, represented by transdiaphragmatic pressure (Pdi), and neural respiratory drive, expressed as the corrected root mean square (RMS) of the diaphragmatic electromyogram (EMGdi), both provide vital information to select the proper IMT device and loads in COPD, therefore contributing to the curative effect of IMT. Pdi and RMS of EMGdi (RMSdi%) were measured and compared during inspiratory resistive training and threshold load training in stable patients with COPD.

          Patients and methods

          Pdi and neural respiratory drive were measured continuously during inspiratory resistive training and threshold load training in 12 stable patients with COPD (forced expiratory volume in 1 s ± SD was 26.1%±10.2% predicted).


          Pdi was significantly higher during high-intensity threshold load training (91.46±17.24 cmH 2O) than during inspiratory resistive training (27.24±6.13 cmH 2O) in stable patients with COPD, with P<0.01 for each. Significant difference was also found in RMSdi% between high-intensity threshold load training and inspiratory resistive training (69.98%±16.78% vs 17.26%±14.65%, P<0.01).


          We concluded that threshold load training shows greater mobilization of Pdi and neural respiratory drive than inspiratory resistive training in stable patients with COPD.

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          Most cited references 19

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          Impact of inspiratory muscle training in patients with COPD: what is the evidence?

          A meta-analysis including 32 randomised controlled trials on the effects of inspiratory muscle training (IMT) in chronic obstructive pulmonary disease (COPD) patients was performed. Overall and subgroup analyses with respect to training modality (strength or endurance training, added to general exercise training) and patient characteristics were performed. Significant improvements were found in maximal inspiratory muscle strength (P(I,max); +13 cmH₂O), endurance time (+261 s), 6- or 12-min walking distance (+32 and +85 m respectively) and quality of life (+3.8 units). Dyspnoea was significantly reduced (Borg score -0.9 point; Transitional Dyspnoea Index +2.8 units). Endurance exercise capacity tended to improve, while no effects on maximal exercise capacity were found. Respiratory muscle endurance training revealed no significant effect on P(I,max), functional exercise capacity and dyspnoea. IMT added to a general exercise programme improved P(I,max) significantly, while functional exercise capacity tended to increase in patients with inspiratory muscle weakness (P(I,max) <60 cmH₂O). IMT improves inspiratory muscle strength and endurance, functional exercise capacity, dyspnoea and quality of life. Inspiratory muscle endurance training was shown to be less effective than respiratory muscle strength training. In patients with inspiratory muscle weakness, the addition of IMT to a general exercise training program improved P(I,max) and tended to improve exercise performance.
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            The assessment of maximal respiratory mouth pressures in adults.

            Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) are simple, convenient, and noninvasive indices of respiratory muscle strength at the mouth, but standards are not clearly established. We review recent literature, update the 2002 American Thoracic Society/European Respiratory Society statement, and propose as the best choice using a flanged mouthpiece for reference values and lower limit of normal (LLN) values as a function of age for adults age up to about 70 years. Because male pressures are higher than female and MEP exceeds MIP, we present 4 linear regression reference equations as a function of age for adults age up to approximately 70 years: Male MIP=120-(0.41xage), and male MIP LLN=62-(0.15xage). Male MEP=174-(0.83xage), and male MEP LLN=117-(0.83xage). Female MIP=108-(0.61xage), and female MIP LLN=62-(0.50xage). Female MEP=131-(0.86xage), and female MEP LLN=95-(0.57xage). (Pressure in cm H2O and age in years.) We discuss normal values in older subjects, estimation of LLN values, and the relationship between vital capacity and respiratory muscle strength, and offer a guide to interpretation of maximal pressure measurements. The approach should allow direct implementation of MIP and MEP in a pulmonary function laboratory.
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              Muscle strength, symptom intensity, and exercise capacity in patients with cardiorespiratory disorders.

              The contribution of muscle strength to symptom intensity and work capacity was examined in normal individuals and patients with cardiorespiratory disorders. Respiratory muscle strengths (maximal inspiratory and expiratory pressures) and peripheral muscle strengths (leg extension, leg flexion, seated bench press, and seated row) were measured in 4,617 subjects referred for clinical exercise testing. Subjects then rated the intensity of leg effort, discomfort with breathing (dyspnea), and chest pain (Borg scale) during an incremental exercise task (100 kpm/min each minute) to capacity on a cycle ergometer. Subjects were classified into groups on the basis of pulmonary function, drug therapy for cardiac disorders, and the presence of chest pain during exercise with electrocardiographic changes indicative of myocardial ischemia. Respiratory and peripheral muscle strengths, normalized for differences in age, sex, and height, were significantly reduced in patients with cardiorespiratory disorders compared with normal individuals. Muscle strength was a significant contributor to symptom intensity and work capacity in both health and disease; a two-fold increase in muscle strength was associated with a 25 to 30% decrease in the intensity of both leg effort and dyspnea and a 1.4- to 1.6-fold increase in work capacity. These results emphasize the need for an integrative approach in the assessment and therapeutic management of exercise intolerance, which considers the contribution of muscle weakness to excessive symptoms and reduced work capacity, in addition to the contribution of ventilatory, gas exchange, and circulatory impairments.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of COPD
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove Medical Press
                02 March 2017
                : 12
                : 773-781
                [1 ]State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou
                [2 ]Department of Respiratory Medicine, The First Affiliated Hospital of Guizhou Medical University, Guizhou, People’s Republic of China
                Author notes
                Correspondence: Luqian Zhou; Rongchang Chen, State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, 151 Yan Jiang Road, Guangzhou 510000, People’s Republic of China, Tel +86 137 6338 3160; +86 158 2024 3582, Fax +86 20 8306 2882, Email zhlx09@ ; chenrc_vip@
                © 2017 Wu et al. This work is published and licensed by Dove Medical Press Limited

                The full terms of this license are available at and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

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