Abstract
Direct chest-wall percussion can reduce breathlessness in Chronic Obstructive Pulmonary Disease and respiratory function may be improved, in health and disease, by respiratory muscle training (RMT). We tested whether high-frequency airway oscillation (HFAO), a novel form of airflow oscillation generation can modulate induced dyspnoea and respiratory strength and/or patterns following 5 weeks of HFAO training (n = 20) compared to a SHAM-RMT (conventional flow-resistive RMT) device (n = 15) in healthy volunteers (13 males; aged 20–36 yrs). HFAO causes oscillations with peak-to-peak amplitude of 1 cm H2O, whereas the SHAM-RMT device was identical but created no pressure oscillation. Respiratory function, dyspnoea and ventilation during 3 minutes of spontaneous resting ventilation, 1 minute of maximal voluntary hyperventilation and 1 minute breathing against a moderate inspiratory resistance, were compared PRE and POST 5-weeks of training (2×30 breaths at 70% peak flow, 5 days a week). Training significantly reduced NRS dyspnoea scores during resistive loaded ventilation, both in the HFAO (p = 0.003) and SHAM-RMT (p = 0.005) groups. Maximum inspiratory static pressure (cm H2O) was significantly increased by HFAO training (vs. PRE; p<0.001). Maximum inspiratory dynamic pressure was increased by training in both the HFAO (vs. PRE; p<0.001) and SHAM-RMT (vs. PRE; p = 0.021) groups. Peak inspiratory flow rate (L.s−1) achieved during the maximum inspiratory dynamic pressure manoeuvre increased significantly POST (vs. PRE; p = 0.001) in the HFAO group only. HFAO reduced inspiratory resistive loading–induced dyspnoea and augments static and dynamic maximal respiratory manoeuvre performance in excess of flow-resistive IMT (SHAM-RMT) in healthy individuals without the respiratory discomfort associated with RMT.
Highlights
Respiratory function is not typically seen as a limitation to activity or exercise performance in healthy individuals, blood flow re-distribution from skeletal muscles has been suggested during near maximal workloads [1]
An interaction effect [F(1,31) = 4.014, p = 0.054] trend highlighted a significant reduction in the SHAM-respiratory muscle training (RMT) (p,0.001), but not the high-frequency airway oscillation (HFAO) group
The main findings of this study were that 5-weeks highfrequency airway oscillation (HFAO) training caused a significant reduction in dyspnoea during an inspiratory resistive loaded challenge and significant increase in peak inspiratory airflow (PIF) during a maximal inhalation
Summary
Respiratory function is not typically seen as a limitation to activity or exercise performance in healthy individuals, blood flow re-distribution from skeletal muscles has been suggested during near maximal workloads [1]. Dyspnoeic perception is a vital constituent of respiratoryinduced activity limitation [6], which processes multiple dimensions: sensations of work/effort, tightness, and air hunger/ unsatisfied inspiration in addition to sensory–perceptual experience, affective distress, or symptom/disease impact or burden domains that may co-exist [7]. COPD is associated with increased respiratory work (41) and skeletal neuromuscular weakness [13]. Such mechanisms can perpetuate a viscous cycle of functional decline (for review see [14]). Experimental elevation of the perception of breathing effort/work can be reproduced via external resistive or elastic loads [15] by volitional hyperpnoea [16], or neuromuscular blockade [17]
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