Abstract
BackgroundWe investigated the influence of diaphragmatic activation control (diaphC) on the relaxation rate, contractile properties and electrical activity of the inspiratory muscles of healthy subjects. Assessments were performed non-invasively using the sniff inspiratory pressure test (SNIP) and surface electromyography, respectively.MethodsTwenty-two subjects (10 men and 12 women) performed 10 sniff maneuvers in two different days: with and without diaphC instructions. For the SNIP test with diaphC, the subjects were instructed to perform intense activation of the diaphragm. The tests with the best SNIP values were used for analysis.ResultsThe maneuver with diaphC when compared to the maneuver without diaphC exhibited significant lower values for: SNIP (p <0.01), maximum relaxation rate (MRR) (p <0.01), maximum rate of pressure development (MRPD) (p <0.01), contraction times (CT) (p = 0.02) and electrical activity of the sternocleidomastoid (SCM) (p <0.01), scalene (SCL) (p = 0.01) and intercostal (CI) (p = 0.03) muscles. In addition, the decay constant (tau, τ) and relaxation time (½ RT) did not present any changes.ConclusionThe diaphragmatic control performed during the SNIP test influences the inspiratory pressure and the contractile properties of inspiratory muscles. This occurs due to changes in the pattern of muscle recruitment, which change force velocity characteristics of the test. Thus, instruction on diaphC should be encouraged for better performance of the SNIP test and for evaluation targeting the diaphragm muscle activity.
Highlights
The measurement of respiratory muscle strength has been used as an index for early detection of pulmonary dysfunction, as well as a parameter to assess the progression of diseases that cause respiratory muscle strength impairment
The maneuver with diaphragmatic activation control (diaphC) when compared to the maneuver without diaphC exhibited significant lower values for: sniff nasal inspiratory pressure (SNIP) (p
The methods commonly used for respiratory muscle assessment measure the Maximum Expiratory Pressure (MEP) and Maximum Inspiratory Pressure (MIP), the latter being complemented by the Sniff Nasal Inspiratory Pressure (SNIP)
Summary
The measurement of respiratory muscle strength has been used as an index for early detection of pulmonary dysfunction, as well as a parameter to assess the progression of diseases that cause respiratory muscle strength impairment It provides prognostic and predictive information on patient survival [1, 2]. Transdiaphragmatic pressure (PDI) has been described as the most accurate measure to assess the strength of the diaphragm muscle [5]. This variable was studied by Miller et al [6] who compared the PDIs obtained by MIP to the ones obtained by sniff. Assessments were performed non-invasively using the sniff inspiratory pressure test (SNIP) and surface electromyography, respectively.
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