Thanks to all list members who replied, both privately and on the list.
My obvious oversight was that tissue oxygen extraction can increase
three fold (from the normal 5 ml O2/100 ml arterial blood to 15 ml
O2/100ml blood). That more than explains the ability during exercise,
to increase VO2 twenty fold, when cardiac output is estimated to
increase only 10 fold.
It was also correctly pointed out that left ventricular ejection
fraction cannot double. I should have said stroke volume.
Thanks for humoring my increasing senility.
regards,
Hansel