Figure 8. Impact of cardiac output (
) on 
.
(A) Effect of three levels of resting 
, (i) 375 ml min−1kg−1, (ii) 250 ml min−1kg−1, and (iii) 125 ml min−1kg−1, on arterial (
) and mixed venous (
) O2 during apnea. Note that reduced 
elevates 
, associated with a reduction in resting 
and reduction in 
at the stage 1–2 transition or inflection point (shown by short black lines). (B) Sensitivity of 
to changes in 
. Note the strong influence of 
on 
, but negligible effect on 
and 
. (C) Simulations in (A) repeated for a step change in 
at apnea onset by (iv) +125 ml min−1kg−1 (e.g. tachycardia), (v) 0 ml min−1kg−1, and (vi) −125 ml min−1kg−1 (e.g. bradycardia), following resting 
. Note that the transient effect of 
is opposite to the resting effect of 
on arterial desaturation during apnea. (D) Sensitivity of 
to acute changes in 
during apnea. Note the strong influence of a step-change in 
on 
, but negligible effect on 
and 
. n = ‘normal’ values.