Assessment of ventilation and respiratory rate by healthy subjects

Ability to judge ventilation (VI) and respiratory rate (RR) was examined in healthy subjects using the standard psychophysical technique of magnitude production. The relationships between objective and subjective magnitudes of VI could be adequately described by power function with the mean exponent 1.9. The mean deviation from the regression line was 3.0%. The requested levels of VI were produced either by changing tidal volume (VT) or RR. Changes in VT resulted in higher exponents of VI judgment. When requesting the subjects to keep VI constant by matching either VT with the imposed changes in RR or vice versa, the lesser acuity was found in adjusting RR to VT than in matching VT with RR. The results indicate that VI is judged on the basis of either VT or RR and is not treated as a concept in its own power. The 'RR' experiments consisted of assessment of RR and breath duration. The relationships between objective and subjective magnitudes of these two parameters were characterized by power functions with the exponents 1.0 and 1.2 respectively and mean deviation from the regression line of 13%. It is speculated that difficulties in adjusting RR to VT depended on a lesser precision in RR judgment.