On the time course of tidal volume, breath-duration, minute volume and end-expiratory CO2 partial pressure on inspiration of gas mixtures with elevated CO2 concentration

Loeschke, H.H.; Katsaros, B.; Albers, C.; Michel, C.C.

Arch Ges Physiol Menschen U Tiere 277(6): 671-683


Accession: 025176258

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The time courses of respiratory minute volume, tidal volume, duration of respiratory period and end-tidal CO2 tension were observed before, during and after changes of inspiratory CO2 fraction in 5 healthy un-selected male subjects. Steady states of respiratory minute volume are established after about 25 min of 5 % CO2. Tidal volume is steady at about 15 minutes of CO2 inhalation. In general the on and off transients of CO2 tension correspond fairly well with the predictions of Defares from the modified regulator theory of Grodins et al. Complications are introduced by different time courses of respiratory frequency and tidal volume in the off transients. Increase of the inspiratory resistance to about double the original value causes only minimal changes in all measured parameters in four of five subjects. In one of five subjects increase of respiratory resistance is followed by a rather unpredictable hyperventilation before, during and after CO2 inhalation. The slow establishment of a steady state or respiratory minute volume during CO2 inhalation is not caused or influenced to any appreciable extent by the inspiratory resistance of the system, because doubling the resistance usually has no more than negligible influence on the time course of respiratory minute volume.