GENDER-RELATED DIFFERENCES IN AIRWAY TONE IN CHILDREN

The effects of gender, volume history, and inhaled atropine and isopro terenol on lung mechanics were assessed in 16 normal boys and 14 norma l girls using lung volumes, flow-volume curves, and oscillatory resist ances. Flows were measured from full and partial forced expiratory flo w-volume curves. Six girls and 6 boys were studied before and after in haled atropine, and 10 boys and 8 girls before and after inhaled isopr oterenol. Girls demonstrated a significant increase in flows on full a nd partial curves with a deep inspiration [Vmax-partial 0.73 +/- 0.34 (SD) to Vmax-full 0.80 +/- 0.37 and 0.83 +/- 0.20 to 1.06 +/- 0.29 TLC /s in each group] and following inhalation of isoproterenol on the par tial curves only (0.73 +/- 0.34 to 0.93 +/- 0.40 TLC/s). Boys showed a small but significant increase in Vmax with isoproterenol on full cur ves but not on partial curves. Following atropine, boys demonstrated a significant increase in Vmax on partial flow-volume curves (0.78 +/- 0.28 to 1.00 +/- 0.35 TLC/s) and a significant decrease in specific re spiratory resistance (7.6 +/- 2.7 to 5.1 +/- 0.9 cmH2O/s), whereas gir ls had no such changes. These data suggest that boys have greater rest ing airway tone than girls and that this tone is less responsive to de ep inspiration and isoproterenol independently, although a combination of isoproterenol and a deep inspiration will produce increased flows in boys. Atropine reduces airway tone predominantly in boys, suggestin g that the increased resting airway tone in boys is partially mediated via the vagus nerve. (C) 1993 Wiley-Liss, Inc.