Fig. 4

Effect on P_aCO₂ of \( \dot{V}{CO}_2 \). Left graph is for a range of \( \frac{{\dot{Q}}_S}{{\dot{Q}}_T} \), with \( {\dot{Q}}_{EC} \) = 3 l/min and \( {\dot{V}}_{\mathrm{SWEEP}} \) = 5 l/min. There is a linear relationship between \( \dot{V}{\mathrm{CO}}_2 \) and P_aCO₂, which is steeper at high pulmonary shunt fractions. Right graph is for a range of \( {\dot{Q}}_{EC} \), with \( \frac{{\dot{Q}}_S}{{\dot{Q}}_T}=0.5 \) and \( {\dot{V}}_{\mathrm{SWEEP}} \) = 5 l/min. P_aCO₂ rises as \( {\dot{Q}}_{EC} \) falls, but for \( {\dot{Q}}_{EC} \) above 2 l/min, the changes are relatively small, but become larger with higher \( \dot{V}{\mathrm{CO}}_2 \)