Reference Values for Respiratory Muscle Strength in Children and Adolescents

Abstract

Background: Measurement of respiratory muscle function is important in the diagnosis of respiratory muscle disease, respiratory failure, to assess the impact of chronic diseases, and/or to evaluate respiratory muscle function after treatment.

Objectives: To establish reference values for maximal inspiratory and expiratory pressure, and the tension-time index at rest in healthy children and adolescents aged 8-19 years, as well as to present sex- and age-related reference centiles normalized for demographic and anthropometric determinants.

Methods: In this cross-sectional observational study, demographic, anthropometric, and spirometric data were assessed, as well as data on respiratory muscle strength (PImax and PEmax) and work of breathing at rest (TT0.1), in a total of 251 children (117 boys and 134 girls; mean age 13.4 ± 2.9 years). Reference values are presented as reference centiles developed by use of the lambda, mu, sigma method.

Results: Boys had significantly higher PImax and PEmax values. Next to sex and age, fat-free mass appeared to be an important predictor of respiratory muscle strength. Reference centiles demonstrated a slight, almost linear increase in PImax with age in boys, and a less steep increase with age in girls. TT0.1 values did not differ between boys and girls and decreased linearly with age.

Conclusion: This study provides reference values for respiratory muscle strength and work of breathing at rest. In addition to sex and age, fat-free mass was found to be an important predictor of respiratory muscle strength in boys and girls.

Keywords: Adolescents; Children; Reference values; Respiratory muscle strength; Tension time index.

Fig. 1

Age- and sex-related reference values for absolute P_Imax (maximal inspiratory mouth pressure) in boys (a) and girls (b), as well as for P_Imax normalized for fat-free mass (FFM) in boys (c) and girls (d). The thick solid line represents the 50th percentile (P50); dotted lines correspond to the 10th, 25th, 75th, and 90th percentiles (P10, P25, P75, and P90, respectively); solid lines indicate the 3rd and 97th percentiles (P3 and P97, respectively).

Fig. 2

Age- and sex-related reference values for absolute P_Emax (maximal expiratory mouth pressure) in boys (a) and girls (b), as well as for P_Emax normalized for fat-free mass (FFM) in boys (c) and girls (d). The thick solid line represents the 50th percentile (P50); dotted lines correspond to the 10th, 25th, 75th, and 90th percentiles (P10, P25, P75, and P90, respectively); solid lines indicate the 3rd and 97th percentiles (P3 and P97, respectively).

Fig. 3

Age-related reference values for absolute T_T0.1 (noninvasive tension time index) at rest (a) as well as for T_T0.1 at rest normalized for fat-free mass (FFM) (b). The thick solid line represents the 50th percentile (P50); dotted lines correspond to the 10th, 25th, 75th, and 90th percentiles (P10, P25, P75, and P90, respectively); solid lines indicate the 3rd and 97th percentiles (P3 and P97, respectively).