Influence of ethnicity and gender on airway function in preterm infants

While maximal expiratory flow at functional residual capacity, calculated from partial expiratory flow volume curves (V'max(FRC)), is a valuable measure of peripheral airway function in infants, limited data are available in preterm infants despite their high prevalence of respiratory problems. To investigate the influence of gender and ethnic group, V'max(FRC) and other indices of respiratory function were measured in 28 black and 28 white preterm infants (50% female in each group) at time of discharge from the neonatal unit (mean [SD] weight 2.36 [0.3] kg, postnatal age 19 [9] d). No infant had any history of cardiorespiratory disease and all were born to non-smoking mothers. V'max(FRC) tended to be higher in girls than boys (115 versus 94 ml.s(-1) [95% CI: -5; 47]) but there was no significant difference in this parameter between black and white infants (111 versus 98 ml.s(-1) [95% CI of difference: -12; 40]). Respiratory resistance (R-rs) was significantly lower in black than white infants (95% CI: -2.9; -0.4 kPa.L-1.s) and tended to be lower in female than male infants (95% CI: -2.3; 0.2 kPa.L-1.s). Similarly, time to peak tidal expiratory flow as a proportion of total expiratory time (t(PTEF):t(E)) was significantly longer in black than white (95% CI: 0.06, 0.20) and in female than male (95% CI: 0.02, 0.15) infants. These findings suggest that certain parameters of airway function may be influenced by both ethnic group and gender in preterm infants, both of which should therefore be taken into account when investigating the effects of disease and/or therapeutic interventions in this group.