Breathing pattern and lung volumes during exercise

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Abstract
The interrelationships of ventilation (.ovrhdot.V), tidal volume (VT), inspiratory (TI), expiratory (TE) and total breath (Ttot) durations, mean inspiratory (VT/TI) and expiratory (VT/TE) flows and lung volumes were studied in normal [human] subjects at rest and during exercise on a cycle ergometer. The ergometric load was increased by 10 W every min, from 0-200 W. The TI/Ttot ratio increased with .ovrhdot.V in the range 15-60 1 .cntdot. min-1, indicating that with increasing .ovrhdot.V the rate of increase of VT/TI decreased whereas that of VT/TE increased. Possible mechanisms responsible for the difference in behavior of VT/TI and VT/TE are discussed. The VT-TI and VT-TE relationships both displayed 3 ranges with breakpoints at tidal volumes of .apprx. 1.4 and 2.41. The relations of TI and TE to end-inspiratory volume were approximately linear over the entire VT range studied, whereas the relations of TI and TE to end-expiratory volume showed 3 ranges with different characteristics. The termination of inspiration during cycle exercise is dependent on volume-related afferent feedback from the lungs and/or chest walls, not only in the high but also in the low volume range.