Determinants of inspiratory muscle function in healthy children

Background

Children are affected by disorders that impact on the respiratory muscles. Inspiratory muscle function can be assessed by the non-invasive Tension-Time Index of the inspiratory muscles (TTI_mus). Our objectives were to identify the determinants of TTI_mus in healthy children and to report normal values of TTI_mus in this population.

Methods

We measured weight, height, upper arm muscle area (UAMA), and TTI_mus in 96 children aged 6-18 years. The level and frequency of aerobic activity was assessed by questionnaire.

Results

TTI_mus was significantly lower in male subjects (0.095 ± 0.038, mean ± SD)) compared to female subjects (0.126 ± 0.056) (p = 0.002). TTI_mus was significantly lower in regularly exercising (0.093 ± 0.040) compared to non-exercising subjects (0.130 ± 0.053), (p < 0.001). TTI_mus was significantly negatively related to age (r = −0.239, p = 0.019), weight (r = −0.214, p = 0.037), height (r = −0.355, p < 0.001), and UAMA (r = −0.222, p = 0.030). Multivariate logistic regression analysis revealed that height and aerobic exercise were significantly related to TTI_mus independently of age, weight, and UAMA. Predictive regression equation for TTI_mus in male subjects was: TTI_mus = 0.228 − 0.001 × height (cm), and in female subjects: TTI_mus = 0.320 − 0.001 × height (cm) .

Conclusion

Gender, age, anthropometry, skeletal muscularity, and aerobic exercise are significantly associated with indices of inspiratory muscle function in children. Normal values of TTI_mus in healthy children are reported.