Changes in the shape and timing of respiratory neural output can serve as potent load-compensatory mechanisms, with a short inspiratory time and convex rising phase being the most economical.
Animal findings suggest neural timing optimizes VT under load; leaves open translation to human respiratory mechanics or support.
We recently described a model for the relation between respiratory neural and mechanical outputs (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 51: 963-1001, 1981). In this communication we utilize the model to address the following questions. 1) How sensitive is tidal volume (VT) to shape and timing of respiratory neural output (N)? 2) How effective are shape and timing characteristics of N in load compensation? 3) For a given VT, what is the most economical shape and timing of N? Using different values of passive respiratory mechanics, we generated the VT profiles associated with theoretical N waveforms having different shape and timing parameters. We found that 1) with normal mechanics VT is moderately sensitive to inspiratory time (TI) but not to shape of N, whereas with high resistance and short TI, VT is very sensitive to shape and timing; 2) changes in shape, within the physiological range, can serve as potent load-compensatory mechanisms; and 3) for a given VT, the most economical (lowest mean pressure) N pattern is one with a very short TI and a rising phase that is convex to time axis. This holds true even with high resistance.
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Younes et al. (1984) studied this question.
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