| Popis: |
The slope of in vivo CO 2 titration curve ( in vivo slope, d[HC0 − 3 ]p/dpHp, unit: slyke) changes with the time of exposure to altered P co 2 The effects of change in cardiac output during the titration with high P co 2 on the time course of change in the in vivo slope and on the value of the slope were investigated in anesthetized dogs. The titration was carried out by means of air and 90-min periods of CO 2 , breathing (12% C0 2 –21% O 2 in N 2 ), the in vivo slope being determined at 5, 10, 30, 60 and 90 min of the CO-s breathing. In spontaneously breathing dogs there was a 60% increase in cardiac output during CO 2 breathing and the in vivo slope reached an apparent steady state no later than 10 min. The arterial blood showed a greater slope (13 slyke) than the mixed venous blood (11 slyke) in these dogs. In dogs with controlled ventilation there was no increase in cardiac output during CO 2 breathing and the apparent equilibration of the titration took 30 min. The in vivo slope was the same (8 slyke) in both of arterial and mixed venous blood. The lower slope value in the latter dogs was discussed in relation to a possible increase in the extracellular fluid volume during CO 2 breathing. |
