In: COPD10 Oct 2014
Respiratory muscle performance is measured in terms of strength and endurance. Respiratory muscle strength can be measured using MIP and MEP pressures at the mouth, according to the method of Black and Hyatt. There are a variety of methods to assess RM endurance. It is likely that they test different capacities of the RM. One measure of RM endurance is the MSVC. The MSVC is the highest ventilation that can be sustained for 15 min. However the MSVC is decreased by reduced airway conductance as well as by reduced respiratory muscle endurance. canadian neighbor pharmacy
Since reduced airway conductance is a feature of COPD, it is difficult to compare MSVC results in this group of patients with those obtained in normal subjects.
The most frequently reported method for assessment of RM endurance incorporates inspiratory resistive loading devices. Endurance was measured either as the time a particular load was tolerated or as the maximum load tolerated for a specific time. However, recent reports indicate that variability in breathing pattern and pressure generation by the inspiratory muscles may substantially alter the time a particular load is tolerated. It is apparent that regulating the breathing pattern and fixing the breath-by-breath pressure generation is necessary to evaluate RM endurance by resistive loading, which makes this test more complex than previously reported.
Nickerson and Keens designed a method of measuring RM endurance using a threshold loading device. The pressure load on the inspiratory muscles was determined by the amount of weight applied to an intake valve. By starting at high loads (requiring the generation of pressures near MIP), and allowing rest periods between loads of ten times the duration of the test, the overall time taken to establish a load which could be tolerated for 10 min was quite long. This could be exhausting if the test were used for other than normal subjects.
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