The role of inspiratory muscle training in the management of asthma and exercise-induced bronchoconstriction

Abstract

Asthma is a pathological condition comprising of a variety of symptoms which affect the ability to function in daily life. Due to the high prevalence of asthma and associated healthcare costs, it is important to identify low-cost alternatives to traditional pharmacotherapy. One of these low cost alternatives is the use of inspiratory muscle training (IMT), which is a technique aimed at increasing the strength and endurance of the diaphragm and accessory muscles of respiration. IMT typically consists of taking voluntary inspirations against a resistive load across the entire range of vital capacity while at rest. In healthy individuals, the most notable benefits of IMT are an increase in diaphragm thickness and strength, a decrease in exertional dyspnea, and a decrease in the oxygen cost of breathing. Due to the presence of expiratory flow limitation in asthma and exercise-induced bronchoconstriction, dynamic lung hyperinflation is common. As a result of varying operational lung volumes, due in part to hyperinflation, the respiratory muscles may operate far from the optimal portion of the length-tension curve, and thus may be forced to operate against a low pulmonary compliance. Therefore, the ability of these muscles to generate tension is reduced, and for any given level of ventilation, the work of breathing is increased as compared to non-asthmatics. Evidence that IMT is an effective treatment for asthma is inconclusive, due to limited data and a wide variation in study methodologies. However, IMT has been shown to decrease dyspnea, increase inspiratory muscle strength, and improve exercise capacity in asthmatic individuals. In order to develop more concrete recommendations regarding IMT as an effective low-cost adjunct in addition to traditional asthma treatments, we recommend that a standard treatment protocol be developed and tested in a placebo-controlled clinical trial with a large representative sample.

Respiratory Effects of Thoracic Load Carriage Exercise and Inspiratory Muscle Training as a Strategy to Optimize Respiratory Muscle Performance with Load Carriage

“…Flow-resistive loading typically involves a variable-diameter orifice that subjects must breathe through. The variable-diameter orifice in this type of device acts as a “leak” which increases the inspiratory pressure required to generate a given rate of airflow [101, 104]. Alternatively, pressure-threshold loading requires an individual to generate a predetermined amount of inspiratory pressure in order to open a one-way valve to enable airflow through the device [101, 104].…”

“…Both of these devices can be considered resistance loading devices. Separately, volume loading protocols such as normocapnic hyperpnea, have been employed, which require individuals to maintain a high ventilatory rate relative to their maximum voluntary ventilation [101, 104]. During this training, subjects engage in rebreathing to prevent hypocapnea from occurring.…”

“…The common element of these three loading protocols is that they are all performed at rest, and not while exercising. For a full description of archetypal training protocols for each of these categories of IMT, the reader is referred to [101]. …”

Marine Lipid Fraction Pcso-524™ (lyprinol®/omega-xl®) Of The New Zealand Green-lipped Mussel Does Not Improve Pulmonary And Respiratory Muscle Function In Non-asthmatic Elite Runners

“…Airway inflammation, coupled with acute immunosuppression during periods of high training volume, may put athletes at risk for upper respiratory tract infection and related performance decrements (4, 7, 11, 26). The precise mechanism behind this airway inflammation is unclear (31). While it may not be due to bronchial hyper-reactivity, post-exercise respiratory symptoms (5, 13), or immune cell activation (5, 6, 24), it may be associated with elevated airway neutrophil counts (5, 6, 8, 24), as well as insufficient conditioning of inspired air and osmotic changes that damage the epithelium (3).…”

Mechanisms, measurement and management of exertional dyspnoea in asthma

“…Inspiratory muscle training (IMT) has also been studied in relation to exertional dyspnoea [110]. A Cochrane review including five randomised controlled trials involving a total of 113 patients found that IMT improves respiratory muscle strength as measured by maximal mouth pressures (mean increase 13.34 cmH 2 O), but concluded that there was inadequate evidence to support or refute a role for IMT for asthma [111].…”