Normal values of maximal inspiratory and expiratory pressures with a portable apparatus in children, adolescents, and young adults.

Maximal inspiratory and expiratory mouth pressures (Plmax and PEmax) were measured over a wide age range using a cylindrical mouthpiece and a multiple trial procedure. Two hundred forty-three students and 30 adults were studied. In addition, a comparison of a cylindrical and a scuba-type mouthpiece was made in 16 subjects. Fifty percent of the subjects required five or more trials to achieve their maximal mouth pressures. Higher PEmax values were obtained using a cylindrical mouthpiece than with a scuba-type mouthpiece in 15 of the 16 subjects tested. Plmax was not affected by mouthpiece type. Males had higher Plmax and PEmax values than females except in the 8-10 years age group. Maximal mouth pressures correlated with age in boys only. Technical considerations, such as the number of trials and the type of mouthpiece used, are important determinants of maximal mouth pressure values.