[The dead space in volitional changes in respiratory volume]

The objective of the investigation was to assess changes of the dead space under conditions of volitional changes of the respiratory volume. The authors assessed therefore in repeated experiments in 11 healthy volunteers basic respiratory variables and the effective dead space using a Mijnhardt spirometer at rest and during cortically conditioned changes of the tidal volume. When the breath deepens the effective dead space reaches higher absolute values, but the relative values decline. When the breathing is more shallow, the reverse occurs. Thus e. g. in men of the investigated group a mean value of the respiratory volume at rest was assessed which amounted to 0.74 +/- 0.10 l, the relative dead space declined to 19 +/- 7%, when breathing was shallow it rose to 37 +/- 10%.