Força muscular respiratória, valores de referência, características psicométricas e aplicabilidade clínica em crianças saudáveis

Abstract

Introduction and Aims: The assessment of respiratory muscle mechanics, structure, and function is essential both in research and in clinical practice. These measures are especially useful in patients with respiratory symptoms and neuromuscular diseases, contributing to the diagnosis, treatment effectiveness, and patient follow-up. It is essential to know the normality values in healthy populations so that we can observe, in certain pathological conditions, the presence of decreased respiratory muscle strength and quantify it objectively, especially in children population where methodological variations can influence the acquisition of these measures. Therefore, this thesis aimed to evaluate respiratory muscle strength in healthy children through maximal respiratory pressures, inspiratory and expiratory (PImax and PEmax, respectively), and sniff nasal inspiratory pressure (SNIP), identifying methodological differences and the psychometric properties of these measures. For this, three objectives were described: 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 age group; 3) Methodologically compare the reference values of maximal respiratory pressures in healthy children between two Brazilian studies. 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 considering the correlations observed with the independent variables: age, weight, and sex. 3) We conducted comparisons of two studies carried out with Brazilian children aged 6 to 11 years. Lanza et al. (2015) developed a multicenter study and Marcelino et al. (2021) in a single center. Both followed the American Thoracic Society/European Respiratory Society (ATS/ERS) recommendations, and Marcelino et al. also partially followed the Brazilian Society of Pulmonology and Tisiology (SBPT) recommendations. Data were analyzed using absolute data comparisons and reference equations between studies, as well as comparisons within each study individually. 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 9-11 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) A total of 428 children aged 6 to 11 years (121 by Marcelino et al. and 307 by Lanza et al.) were evaluated. Data from both studies were requested from the authors and later compared. Following this analysis, Marcelino et al. obtained higher reference values for PImax [88 cmH2O (68.5 - 109) vs 80 cmH2O (64-98)] and PEmax [96 cmH2O (82 - 117) vs 80 cmH2O (68-92)], as well as stratified by sex (p < 0.01) and age groups (p<0.001). Lanza et al. had lower 95% confidence intervals in both pressure values stratified by sex when compared to Marcelino et al. Both studies had moderate to large effect sizes in samples divided by sex and age groups. 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) Despite the methodological differences, and the use of different manometers, both were carried out with appropriate methodologies, allowing the application of reference values and equations according to available resources, experience in handling equipment and training of evaluators in performing maneuvers. Final conclusion: According to the results of the studies, we determined a reliable number of SNIP maneuvers to be performed (12 maneuvers) and new reference values for maximal respiratory pressures, considering the importance of defining these normal values using recommended methodologies and equipment that provide appropriate measures, minimizing as much as possible divergences that they occur due to the absence of standardization in studies.