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Respiration 2006;73:143–144 DOI: 10.1159/000091529

Inspiratory Muscle Training: A Way to Breathe More Easily
Enrico Clini Stefania Costi
Department of Pulmonary Rehabilitation, Fondazione Villa Pineta and University of Modena, Pavullo, Italy

Inspiratory muscles have been specifically targeted for training patients with chronic obstructive pulmonary disease (COPD). So far, therationale for training has been questioned. Although inspiratory muscle strength is low in most of these patients, mainly because of the mechanical disadvantage due to hyperinflation, respiratory muscles are likely to adapt to the chronically imposed work of breathing [1], and the diaphragmatic contractile fatigue is rarely observed even during strenuous exercise in stable disease [2]. On the onehand, respiratory muscles, unlike the peripheral muscles, apparently do not to suffer from deconditioning, and a training intervention does not appear justified on this basis. On the other hand, the work of the diaphragm is clearly increased during exercise [3], thus leading to perception of ‘difficult inspiration’, ‘shallow breathing’ or ‘unrewarded inspiration’ [4], especially in some COPD patientswhose respiratory muscle adaptation may be insufficient. Therefore, if inspiratory muscle training (IMT) is able to increase the maximal inspiratory muscle pressure (PImax), and to change the structure of these muscles, it seems reasonable to expect that symptoms will be reduced while exercising, thus turning these effects into a functional benefit. These positive effects have been confirmed in COPDpatients with inspiratory muscle weakness by a recent systematic review [5].

IMT programs require regular supervision but are relatively inexpensive and can be conducted at home. One study investigating the long-term effect of IMT suggested that benefits wear off rapidly when training is discontinued [6]. Whether training conducted with appropriate load also translates into increased exercisetolerance and better quality of life is still unclear, thus making the evidence-based guidelines [7, 8] to conclude that IMT should not be a routine component in the rehabilitation programs. In this issue of Respiration, Weiner et al. [9] pointed out a practical problem in the management of COPD patients showing weakness of their inspiratory muscles. This may cause, in turn, the inability to generateadequate flow to assure lung deposition when using dry powder inhalers (DPIs), which are commonly prescribed to deliver bronchodilators to these patients. Bioavailability is predictive of the clinical effect of the inhaled drug [10] and peak inspiratory flow (PIF) measurements reflect the patient’s ability to properly inhale the drug. Authors have found that almost 20% of the most compromisedpatients (staged according to the forced expiratory volume in 1 s) are not able to generate enough flow to assure proper inhalation (and therefore deposition) from one of the most popular and commonly used devices (Turbohaler) and that, in addition, PIF values cor-

© 2006 S. Karger AG, Basel 0025–7931/06/0732–0143$23.50/0 Fax +41 61 306 12 34 E-Mail Accessible onlineat:

Dr. Enrico Clini Fondazione Villa Pineta Division of Pneumology and Pulmonary Rehabilitation, Via per Gaiato 127 IT–41020 Pavullo (Italy) Tel./Fax +39 0536 42039, E-Mail

relate with a patient’s PImax [9]. Since the maximal inspiratory flow, at a given volume, depends both on airway resistance and on strength as well as the speed of shortening of theinspiratory muscles [11], it is reasonable that IMT should enable those COPD patients with respiratory muscle weakness to assure adequate drug deposition in their lungs and, therefore, bronchodilation. Indeed, Weiner et al. [9] have demonstrated that IMT at adequate load significantly increased PImax and PIF in weak COPD patients.

This problem, outside a clinical trial, may involve about one...
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