Maximal respiratory pressures in children.

Maximal inspiratory ( PImax ) and expiratory ( PEmax ) pressures were measured 7 separate times during 1 month in 40 children (13 males and 27 females, 101 to 208 months of age). After an initial period of learning, the Pimax for 20 repeated efforts was 11.1 +/- 2.4 kPa and the PEmax was 14.0 +/- 3.6 kPa. Mean values for the 20 efforts were 83% of PImax and 84% of PEmax . Individual coefficient of variation was 10% for PImax and 11% for PEmax . Postpubertal boys had higher pressures than did girls, primarily related to their greater muscle area. Pressures correlated with upper arm muscle area in both sexes and with age and height in boys. The PEmax was lower in these children than in previously reported normal adults, probably because of less muscle development. The PImax was similar to adult values, suggesting that a factor in addition to muscle strength influences inspiratory pressures in children.