RESPIRATORY MUSCLE STRENGTH, REFERENCE VALUES, PSYCHOMETRIC CHARACTERISTICS AND CLINICAL APPLICABILITY IN HEALTHY CHILDREN
Respiratory muscle strength; children; reference values
Introduction: Respiratory muscles play as the main function pulmonary ventilation, functionally dividing into three groups: the diaphragm, the rib cage muscles, and the abdominal muscles. In clinical practice, this musculature strength is measured by the pressures generated mainly in voluntary and non-invasive maneuvers, such as through the maximum inspiratory and expiratory pressures (PImax and PEmax, respectively) and sniff nasal inspiratory pressure (SNIP). Aims: 1) To analyze the reliability of the SNIP maneuver in a single evaluation and determine the number of maneuvers necessary to reach the maximum SNIP peak in healthy children 6-11 years old; 2) Determine reference values for maximum respiratory pressures in healthy children of the same previous age group; and 3) To compare the reference values of maximal respiratory pressures between two Brazilian studies in this population. Materials and Methods: 1) This cross-sectional study included 121 healthy children with normal lung function who performed 12 to 20 SNIP maneuvers, with 30 seconds of rest between them. Reliability was tested using the intraclass correlation coefficient (ICC), standard error of measurement (SEM), minimum detectable change (MDC) and Bland-Altman analysis for concordance. 2) At least three tests of each maximum respiratory pressure, PImax and PEmax, were performed on 121 healthy children, with a minimum duration of 1.5 seconds, plateau of one second and one minute rest between tests. Was applied a stepwise multiple linear regression analysis for PImax and PEmax taking into account the correlations observed with the independent variables: age, weight and sex. 3) The methodology used by Marcelino et al. is the same methodology as in study 2. While Lanza et al. developed the reference equations through a multicenter study, with a sample of 318 children aged 6 to 11 years. Maximum respiratory pressures were measured with an aneroid manometer. To compare both methodologies, the mean differences in pressures between the studies were compared and differences between genders and age groups were observed through p value and effect size. Results: 1) ICC and the corresponding confidence interval (CI) between the highest measure and the first reproducible maneuver were 0.752 (0.656 - 0.824), SEM = 10.37 cmH2O and MDC = 28.74 cmH2O. For children aged 6-7 years, the ICC was 0.699 (0.427 - 0.822), SEM = 10.76 cmH2O and MDC = 29.82 cmH2O; for children aged 8-11 years, the ICC was 0.774 (0.662 - 0.852), SEM = 9.74 cmH2O and MDC = 26.05 cmH2O. For girls, the ICC was 0.817 (0.706 - 0.889), SEM = 9.40 cmH2O and MDC = 26.05 cmH2O; for boys, the ICC was 0.671 (0.477 - 0.798), SEM = 11.51 cmH2O and MDC = 31.90 cmH2O. Approximately 80% of the total sample reached the highest SNIP before the 10th maneuver. 2) Boys achieved higher values of maximum respiratory pressures about girls. Associations of pressures between ages showed an increase according to the age groups studied (6-7, 8-9 and 19-11 years) with a moderate effect size for both. Independent variables height, weight, age and sex were positively correlated with PImax, but age and sex persisted in the equation (PImax = 24.630 + 7.044 * age (years) + 13.161 * sex (0 for girls and 1 for boys)). PEmax was positively correlated with height, weight and age, making the equation the variables age in girls and weight in boys [PEmax (girls) = 55.623 + 4.698 * age (years) and PEmax (boys) = 82.617 + 0.612 * weight (kg)]. 3) Close mean differences were found between absolute data from each study and the values found by the developed equations. Furthermore, in the comparisons between sexes and age groups in the studies, medium to wide effect sizes were identified. Lanza et al. had lower 95% confidence intervals for both sexes. Conclusions: 1) SNIP demonstrated moderate reliability between the maneuvers in children aged 6-11 years; older children and girls reached SNIP peak faster. Therefore, the results indicated that 12 maneuvers were sufficient for healthy children to reach the maximum SNIP peak. 2) This study determined new reference equations for maximum respiratory pressures in healthy children aged 6-11 years, including variables such as age, sex and weight, using the specific methodology recommended by ATS/ERS and BSPT. 3) Studies analyzed presented similar reference values in healthy Brazilian children, despite the different methodologies adopted. Thus, we can conclude that this thesis presents studies with important clinical significance in healthy children so that we can reliably assess respiratory muscle strength in this population using reliable methodologies.