Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2000: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1999: ¥2,900,000 (Direct Cost: ¥2,900,000)
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Research Abstract |
In healthy humans, the breathlessness intensity (BS) during exercise is related to pulmonary ventilation (V_E), stimulation to respiratory chemoreceptors and various sensory receptors existing at tracheae, lungs and respiratory muscles. The present study examined how metaboreceptor in the respiratory muscles is involved in breathlessness during exercise. Subjects performed light to heavy exercise on a cycle ergometer, during which BS, V_E, and Oxy and DeoxyHb/Mb contents (Hb : hemoglobin, Mb : myoglobin) of each of the parasternal internal intercostal muscle, the serratus anterior muscle (both inspiratory muscles) and the external abdominal oblique muscle (expiratory muscle). The subject breathed under 4 conditions with varying metabolic rates of the respiratory muscles : (1) breathing air throtugh a respiratory mask or (2) through the mask plus a tubing with 500-ml dead space, and (3) breathing air or (4) 40% O_2, each through an one-way respiratory valve. Under any conditions of brea
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thing, BS was related to V_E and DeoxyHb/Mb contents of the inspiratory muscles, but not to those of the expiratory muscle and OxyHb/Mb contents. A multiple linear regression analysis evidenced the following two relationships : BS=0.09[ΔV_E] 0.05 [Δ DeoxyHb/Mb]-1.37 (r^2=0.87±0.04, n=7, Δ : difference from preexercise values) when breathing with less inspiratory resistance through the mask alone, and BS=0.10 [ΔV_E]+ 0.08 [ΔDeoxyHb/Mb]-2.50 (r^2=0.93±0.03, n=7) when breathing with higher inspiratory resistances through the mask plus other apparatus. The results suggest that (1) BS during exercise is related to V_E and DeoxyHb/Mb contents of the inspiratory muscles as an index of O_2 consumption of the muscles, (2) with less inspiratory resistance (as in natural spontaneous breathing), the BS is mostly proportional to V_E, (3) with higher inspiratory resistances (as in breathing through a breathing valve or a snorkel), BS is augmented by increased DeoxyHb/Mb of the inspiratory muscles even at a given level of V_E, and (4) restriction of the respiratory muscle movements (as in swimming) results in lower DeoxyHb/Mb of the inspiratory muscles but greater BS, as compared to natural breathing at a given level of V_E. Less
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