Hyperpnoea induced by forced breathing

The absence of apnoea after forced breathing has frequently been recorded, but seems to have received little attention, presumably since it appears contrary to accepted ideas of the chemical control of respiration. Boothby (1912), with himself as subject, found hyperpnoea instead of apnoea, but did not succeed in demonstrating any cause for the phenomenon. He suggested that the hyperpnoea might be due to anoxia following diminished medullary circulation, and recorded that his systolic blood pressure fell 20 mm. Hg as a result of forced breathing, whereas the blood pressure of Dr Haldane, who showed apnoea after forced breathing, hardly fell at all. With the increasing recognition of a variety of nervous factors in respiratory control it appeared that this problem might be worth further investigation.