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Contra-indications

Inspiratory muscle training is associated with large negative pressure swings within the chest (intra-thoracic decompression), and this naturally engenders concern regarding barotrauma-related events. For example, clinicians sometimes express concern regarding the risks of IMT for patients with bullae/blebs, especially those with COPD.

Implicitly, the measurement of maximal respiratory pressures is associated with larger pressure changes, so it's perhaps appropriate to also consider the risks associated with these measurements, since they represent a "worst case scenario" for IMT. The first published measurements of maximal respiratory pressures were made by Black & Hyatt in the late 1960s, and the first studies of inspiratory muscle training were made by Leith & Bradley in 1976. Thus, the research base spans over 40 years, but there is no mention of any complications or adverse events in any of the studies within the published literature. In other words, of the hundreds of studies of inspiratory muscle training and/or maximal inspiratory mouth pressure measurement (incorporating many thousands of patients), no study has ever reported a patient withdrawal due to an event precipitated by barotrauma. Similarly, there are no case studies of IMT reporting isolated incidents of adverse events during the treatment, or assessment of any person undertaking measurement of maximal inspiratory pressures, or inspiratory muscle training. Despite the intra-thoracic pressure swings, even patients with heart failure experience no deterioration of their cardiac output during training (McConnell et al., 2005).

Notwithstanding this, there are some theoretical risks associated with sub-atmospheric pressures within the chest, throat, inner ear and sinuses. Accordingly, there are some conditions in which IMT may not be appropriate:

• A history of spontaneous pneumothorax (i.e., not due to traumatic injury)
• A pneumothorax due to a traumatic injury that has not healed fully
• A burst eardrum that has not healed fully, or any other condition of the eardrum

There is also an important sub-group of asthma patients for whom IMT is inappropriate, i.e., those with unstable asthma and abnormally low perception of dyspnoea. In these patients, it is the disruption of the normal relationship between dyspnoea and bronchoconstriction that is thought to contribute to their poor adherence to medication and consequent clinical instability (Magadle et al., 2002). Since IMT may reduce their perception still further, it is inadvisable.

Unlike pharmacological treatments, there are no side effects or drug interactions.

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