EFFECT OF INCREASED VENTILATION ON RESISTIVE LOAD DISCRIMINATION

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Abstract
The ability of normal subjects to detect the addition of external resistive loads was determined at rest and when ventilation was increased to more than 30 l/min by CO2 administration or exercise. Tidal volume, flow and mouth and transpulmonary pressures were recorded during resistive load discrimination using standard psychophysical techniques. The mean resistance detection threshold was 0.40 .+-. 0.06 cm H2O/l per s at rest, 0.36 cm H2O/l per s during administration of CO2 and 0.44 cm H2O/l per s with exercise. The Weber fraction was 0.28 .+-. 0.04 at rest, 0.29 .+-. 0.08 with CO2 and 0.34 .+-. 0.04 with exercise. The lack of change in the ability to detect resistive loads when ventilation was increased was surprising because changes in both pressure and flow were tripled. Apparently, resistance or something like it is perceived, rather than change in flow or pressure.