The effect of the rate of breathing on the maximum breathing capacity determined with a new spirometer.

Very few quantitative observations have been reported on the effect of rate of breathing on the voluntary maximum breathing capacity (M.B.C.). Proctor and Hardy (1949) found that the M.B.C. was achieved at a rate of 30 respirations per minute (R.P.M.). At higher rates of breathing the ventilatory capacity was diminished. These observations are contrary to the findings of other investigators who regard a fast rate of breathing as essential in producing the largest value for the M.B.C. (Gray and Green, 1945; Baldwin, Cournand, and Richards, 1948). None of these investigators used spirometers which had been tested for recording errors (Bernstein and Mendel, 1951), nor were the observations made at controlled rates of breathing. The effect of rate of breathing on the M.B.C. of a group of normal subjects has been investigated. This work has been performed on a spirometer which is substantially free from recording error. It has been suggested that to control the rate of breathing impairs the subject's performance, but evidence is provided here to show that there is no sound basis for that opinion.