Non-invasive tension time index in relation to severity of disease in children with cystic fibrosis

Extubation in the pediatric intensive care unit: predictive methods. An integrative literature review

For extubation in pediatric patients, the evaluation of readiness is strongly recommended. However, a device or practice that is superior to clinical judgment has not yet been accurately determined. Thus, it is important to conduct a review on the techniques of choice in clinical practice to predict extubation failure in pediatric patients. Based on a search in the PubMed®, Biblioteca Virtual em Saúde, Cochrane Library and Scopus databases, we conducted a survey of the predictive variables of extubation failure most commonly used in clinical practice in pediatric patients. Of the eight predictors described, the three most commonly used were the spontaneous breathing test, the rapid shallow breathing index and maximum inspiratory pressure. Although the disparity of the data presented in the studies prevented statistical treatment, it was still possible to describe and analyze the performance of these tests.

Força muscular respiratória e qualidade de vida em crianças e adolescentes com fibrose cística

RESUMO A fibrose cística (FC) é uma doença genética multissistêmica caracterizada por obstrução crônica que, associada a outras alterações pulmonares, pode comprometer a força muscular respiratória (FMR) e, em consequência, interferir no desempenho de atividades típicas da infância, alterando a qualidade de vida (QV) dessa população. O objetivo do estudo foi avaliar a relação entre FMR e QV de crianças e adolesceantes com FC. Trata-se de um estudo transversal, que incluiu pacientes com idades entre 6 e 14 anos, provenientes de um centro de referência no Brasil. Realizou-se avaliação antropométrica e da FMR, esta utilizando as pressões inspiratória (PImáx) e expiratória máximas (PEmáx) por meio da manovacuômetria digital (Globalmed® MVD300). Aplicou-se o Cystic Fibrosis Questionnaire (QFC), questionário específico para a avaliar a QV nessa doença, nas versões para crianças (QFC-C) e para os pais ou responsáveis (QFC-R). A gravidade da doença foi classificada segundo o escore de Schwachman Doeurshuk (ESD). Dados sobre a colonização de bactérias e o genótipo da doença foram consultados por meio da análise dos prontuários. Analisou-se os dados por meio do software SPSS version 20.0 for Windows. Após o teste Shapiro-Wilk, aplicou-se o teste de correlação de Pearson ou Spearman. Em toda a análise foi adotado nível de significância de 5%. Participaram do estudo 28 crianças (15 meninos) com média de idade de 10,10±1,79 anos, as quais apresentaram FMR próxima ao predito e pontuações do QFC indicando boa QV. O ESD relacionou-se negativamente com domínio digestivo (p=0,03; rho=-0,400). A PEmáx apresentou correlação negativa com domínio corpo do QFC-R (p=0,002; rho=-0,426) e com domínio tratamento do QFC-C (p=0,01; rho=-0,453). A PImáx apresentou correlação positiva com os domínios físico (p=0,03; rho=0,410), emocional (p=≤0,001; rho=0,573) e tratamento (p=≤0,01; rho=-0,605) do QFC-C. A PImáx também mostrou correlação positiva com o domínio respiratório (p=0,01; rho=0,572) do QFC-R. Em conclusão, identificou-se associação entre domínios da QV e FMR, bem como com o ESD e aspectos nutricionais. Essa amostra apresentou valores de FMR acima do esperado e boa QV.

Clinimetric evaluation of muscle function tests for individuals with cystic fibrosis: A systematic review

Accurate testing of muscle function is essential in individuals with cystic fibrosis (CF). A literature search was conducted in MEDLINE, CENTRAL, CINAHL, PEDro, ScienceDirect and Web of Science according to PRISMA and COSMIN guidelines from inception to September 2019 to investigate the clinimetric properties of muscle tests in individuals with CF. The search identified 37 studies (1310 individuals) and 34 different muscle tests. Maximal inspiratory pressure, inspiratory work capacity and quadriceps strength measured by computerised dynamometry were identified as reliable tests of muscle function. The one-minute sit-to-stand test was found to have high reliability but its validity to measure quadriceps strength is unknown. The clinimetric properties of other routinely used tests have not been reported in people with CF. Very different measurement procedures were identified. Inspiratory muscle and quadriceps testing can be considered as reliable but high-quality studies evaluating tests of other muscles function (e.g. muscle endurance) are lacking.

Inspiration for the Future: The Role of Inspiratory Muscle Training in Cystic Fibrosis

Cystic fibrosis (CF) is an inherited, multi-system, life-limiting disease characterized by a progressive decline in lung function, which accounts for the majority of CF-related morbidity and mortality. Inspiratory muscle training (IMT) has been proposed as a rehabilitative strategy to treat respiratory impairments associated with CF. However, despite evidence of therapeutic benefits in healthy and other clinical populations, the routine application of IMT in CF can neither be supported nor refuted due to the paucity of methodologically rigorous research. Specifically, the interpretation of available studies regarding the efficacy of IMT in CF is hampered by methodological threats to internal and external validity. As such, it is important to highlight the inherent risk of bias that differences in patient characteristics, IMT protocols, and outcome measurements present when synthesizing this literature prior to making final clinical judgments. Future studies are required to identify the characteristics of individuals who may respond to IMT and determine whether the controlled application of IMT can elicit meaningful improvements in physiological and patient-centered clinical outcomes. Given the equivocal evidence regarding its efficacy, IMT should be utilized on a case-by-case basis with sound clinical reasoning, rather than simply dismissed, until a rigorous evidence-based consensus has been reached.

Determinants of inspiratory muscle function in healthy children

BACKGROUND

Children are affected by disorders that have an impact on the respiratory muscles. Inspiratory muscle function can be assessed by means of the noninvasive tension-time index of the inspiratory muscles (TTImus). Our objectives were to identify the determinants of TTImus in healthy children and to report normal values of TTImus in this population.

METHODS

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

RESULTS

TTImus was significantly lower in male subjects (0.095 ± 0.038, mean ± SD) compared with female subjects (0.126 ± 0.056) (p = 0.002). TTImus was significantly lower in regularly exercising (0.093 ± 0.040) compared with nonexercising subjects (0.130 ± 0.053) (p < 0.001). TTImus 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 TTImus independently of age, weight, and UAMA. The predictive regression equation for TTImus in male subjects was TTImus = 0.228 - 0.001 × height (cm), and in female subjects it was TTImus = 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 TTImus in healthy children are reported.

Reference Values for Respiratory Muscle Strength in Children and Adolescents

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.

Inspiratory muscle strength relative to disease severity in adults with stable cystic fibrosis

BACKGROUND

Due to heterogeneity in pulmonary disease, current literature may misrepresent inspiratory muscle involvement in cystic fibrosis (CF). This study investigated inspiratory muscle strength (IMS) relative to disease severity in adults with CF.

METHODS

Maximal inspiratory pressure (MIP) was assessed in 58 adults with stable CF grouped by disease severity (20 mild, 20 moderate, 18 severe) and compared to 20 controls. Relationships between MIP, lung function, dyspnea and anthropometrics were evaluated using multivariable linear models.

RESULTS

MIP in cmH2O and %-predicted was decreased in advanced CF lung disease as compared to mild disease and healthy controls (p<0.05). Disease severity accounted for 24% of the variance in IMS after controlling for confounding variables (p<0.001).

CONCLUSIONS

IMS is decreased in some adults with stable CF with moderate and severe pulmonary disease, and is related to dyspnea. Future studies should determine if decreased IMS contributes inefficient breathing patterns, respiratory pump dysfunction, and/or exercise intolerance in advanced CF.

Time constant of inspiratory muscle relaxation in cystic fibrosis

BACKGROUND

Patients with cystic fibrosis (CF) are at increased risk of inspiratory muscle fatigue and respiratory failure. The time constant (τ) of the inspiratory muscle relaxation is a simple bedside test of muscle fatigue. We have compared patients with CF and healthy controls regarding τ and hypothesized that it is negatively associated with severity of lower airway obstruction.

METHODS

For this cross-sectional study, τ after maximal inspiration and spirometric indices (forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC)) were measured.

RESULTS

Fifty-three CF patients (median age 14 y (interquartile range: 11-19.5)) and 53 age- and sex-matched healthy control subjects (14 y (11-19.5)) were recruited. Application of a general linear model revealed that health status (CF vs. non-CF) had a significant effect on τ (P < 0.001), but age group and the interaction of age group with health status did not have significant effects on τ (P = 0.10 and P = 0.71, respectively). Participants with CF had significantly higher τ (253 (188-406)) than control subjects (117 (81-185)) (P < 0.001) and τ was negatively related to FEV1 (r = -0.205; P = 0.031) and FVC (r = -0.294; P = 0.002).

CONCLUSION

Patients with CF have higher τ than healthy controls but the correlation of τ with expiratory flow function is modest.

Determinants of respiratory pump function in patients with cystic fibrosis

Respiratory failure constitutes the major cause of morbidity and mortality in patients with Cystic Fibrosis (CF). Respiratory failure could either be due to lung parenchyma damage or to insufficiency of the respiratory pump which consists of the respiratory muscles, the rib cage and the neuromuscular transmission pathways. Airway obstruction, hyperinflation and malnutrition have been historically recognised as the major determinants of respiratory pump dysfunction in CF. Recent research has identified chronic infection, genetic predisposition, dietary and pharmaceutical interventions as possible additional determinants of this impairment. Furthermore, new methodological approaches in assessing respiratory pump function have led to a better understanding of the pathogenesis of respiratory pump failure in CF. Finally, respiratory muscle function could be partially preserved in CF patients with structured interventions such as aerobic exercise, inspiratory muscle training and non-invasive ventilation and CF patients could consequently be relatively protected from respiratory fatigue and respiratory failure.

Respiratory muscle function in patients with cystic fibrosis

Respiratory muscle function in patients with cystic fibrosis (CF) can be assessed by measurement of maximal inspiratory pressure (Pimax ), maximal expiratory pressure (Pemax ), and pressure-time index of the respiratory muscles (PTImus ). We investigated the differences in maximal respiratory pressures and PTImus between CF patients with no gross hyperinflation and healthy controls and described the effects of pulmonary function and nutrition impairment on respiratory muscle function in this group of CF patients. Forced expiratory volume in 1 sec (FEV1 ), forced vital capacity (FVC) and maximal expiratory flow between 25% and 75% of VC (MEF25-75 ), body mass index (BMI), upper arm muscle area (UAMA), Pimax , Pemax , and PTImus were assessed in 140 CF patients and in a control group of 140 healthy subjects matched for age and gender. Median Pimax and Pemax were significantly lower in CF patients compared to the controls [Pimax  = 74 (57-94) in CF vs. 84 (66-102) in controls, P = 0.009], [Pemax  = 71 (50-95) in CF vs. 84 (66-102) in controls, P < 0.001]. Median PTImus in CF patients compared to controls was significantly increased [PTImus  = 0.110 (0.076-0.160) in CF vs. 0.094 (0.070-0.137) in controls, P = 0.049] and it was significantly higher in CF patients with impaired pulmonary function. In CF patients, PTImus was significantly negatively related to upper arm muscle area (r = 0.184, P = 0.031). These findings suggest that CF patients with no severe lung disease compared to healthy subjects exhibit impaired respiratory muscle function, while CF patients with impaired pulmonary function and nutrition indices exhibit higher PTImus values.

Aerobic exercise and respiratory muscle strength in patients with cystic fibrosis

BACKGROUND

The beneficial role of exercise in maintaining health in patients with cystic fibrosis (CF) is well described. Few data exist on the effect of exercise on respiratory muscle function in patients with CF. Our objective was to compare respiratory muscle function indices in CF patients that regularly exercise with those CF patients that do not.

METHODS

This cross-sectional study assessed nutrition, pulmonary function and respiratory muscle function in 37 CF patients that undertook regular aerobic exercise and in a control group matched for age and gender which consisted of 44 CF patients that did not undertake regular exercise. Respiratory muscle function in CF was assessed by maximal inspiratory pressure (Pimax), maximal expiratory pressure (Pemax) and pressure-time index of the respiratory muscles (PTImus).

RESULTS

Median Pimax and Pemax were significantly higher in the exercise group compared to the control group (92 vs. 63 cm H2O and 94 vs. 64 cm H2O respectively). PTImus was significantly lower in the exercise group compared to the control group (0.089 vs. 0.121). Upper arm muscle area (UAMA) and mid-arm muscle circumference were significantly increased in the exercise group compared to the control group (2608 vs. 2178 mm2 and 23 vs. 21 cm respectively). UAMA was significantly related to Pimax in the exercising group.

CONCLUSIONS

These results suggest that CF patients that undertake regular aerobic exercise maintain higher indices of respiratory muscle strength and lower PTImus values, while increased UAMA values in exercising patients highlight the importance of muscular competence in respiratory muscle function in this population.

Angiotensin-converting enzyme gene polymorphism and respiratory muscle function in infants

OBJECTIVE

Angiotensin-converting enzyme (ACE) gene contains a polymorphism consisting of either the presence (I) or absence (D) of a 287-bp fragment. Recent studies have suggested that the I-allele may be associated with superior exercise endurance; respiratory muscle function may be similarly influenced. The pressure-time index of inspiratory muscles (PTImus) is a measure of the load-capacity ratio of the inspiratory muscles. The objective of this study was to determine whether infants homozygous for the I-allele have lower PTImus compared to infants homozygous for the D-allele or heterozygous I/D.

PATIENTS AND METHODS

One hundred thirty-two infants were studied. ACE genotyping was performed by polymerase chain reaction amplification, using DNA from peripheral blood. PTImus was calculated as (Pi(mean)/Pi(max)) × (T(i)/T(tot)), where Pi(mean) was the mean inspiratory pressure estimated from airway pressure, generated 100 ms after an occlusion (P(0.1)), Pi(max) was the maximum inspiratory pressure and T(i)/T(tot) was the ratio of the inspiratory time to the total respiratory cycle time. Pi(max) was the largest pressure generated during brief airway occlusions performed at the end of a spontaneous crying effort.

RESULTS

Infants with I/I genotype had significantly lower PTImus than infants with either D/D or I/D genotypes (P = 0.000007). ACE genotype was significantly related (P = 0.005) to PTImus measurements, independent of other factors that may affect respiratory muscle function.

CONCLUSION

These results suggest that an association of ACE genotypes with PTImus measurements may exist in infants.