A novel non-invasive method to detect excessively high respiratory effort and dynamic transpulmonary driving pressure during mechanical ventilation.

BACKGROUND: Excessive respiratory muscle effort during mechanical ventilation may cause patient self-inflicted lung injury and load-induced diaphragm myotrauma, but there are no non-invasive methods to reliably detect elevated transpulmonary driving pressure and elevated respiratory muscle effort during assisted ventilation. We hypothesized that the swing in airway pressure generated by respiratory muscle effort under assisted ventilation when the airway is briefly occluded (ΔPocc) could be used as a highly feasible non-invasive technique to screen for these conditions. METHODS: Respiratory muscle pressure (Pmus), dynamic transpulmonary driving pressure (ΔPL,dyn, the difference between peak and end-expiratory transpulmonary pressure), and ΔPocc were measured daily in mechanically ventilated patients in two ICUs in Toronto, Canada. A conversion factor to predict ΔPL,dyn and Pmus from ΔPocc was derived and validated using cross-validation. External validity was assessed in an independent cohort (Nanjing, China). RESULTS: Fifty-two daily recordings were collected in 16 patients. In this sample, Pmus and ΔPL were frequently excessively high: Pmus exceeded 10 cm H2O on 84% of study days and ΔPL,dyn exceeded 15 cm H2O on 53% of study days. ΔPocc measurements accurately detected Pmus > 10 cm H2O (AUROC 0.92, 95% CI 0.83-0.97) and ΔPL,dyn > 15 cm H2O (AUROC 0.93, 95% CI 0.86-0.99). In the external validation cohort (n = 12), estimating Pmus and ΔPL,dyn from ΔPocc measurements detected excessively high Pmus and ΔPL,dyn with similar accuracy (AUROC ≥ 0.94). CONCLUSIONS: Measuring ΔPocc enables accurate non-invasive detection of elevated respiratory muscle pressure and transpulmonary driving pressure. Excessive respiratory effort and transpulmonary driving pressure may be frequent in spontaneously breathing ventilated patients.

Impact of chronic kidney disease on quality of life, lung function, and functional capacity / Repercussão da doença renal crônica na qualidade de vida, função pulmonar e capacidade funcional

OBJECTIVES: To evaluate the impact of the chronic kidney disease (CKD) on quality of life, from the children's and their parents' perspective, respiratory muscle strength, lung function, and functional capacity in children and adolescents. METHOD: Cross-sectional study of children with CKD aged 8 to 17 years. Those incapable of taking the tests were excluded. After an interview, quality of life by Pediatric Quality of Life Inventory) (PedsQLTM), muscular strength, pulmonary function tests, and the 6-minute walking test (6MWT) were applied. Student's t-test, ANOVA (difference in means), and Pearson's coefficient of correlation were used. The level of significance was set at 5%. RESULTS: Of the 40 patients, the mean distance walked at the 6MWT was 396 meters, and the mean final score at the quality of life test as perceived by the children and parents was 50.9 and 51, respectively. From the children's perspective, the transplanted patients had a higher quality of life score when compared to those undergoing hemodialysis (p < 0.001); those who practiced physical activity had better quality of life when compared to the sedentary children (p < 0.001). From the children's and the parents' perspectives, the male gender had a higher quality of life score (p < 0.05). There was a positive correlation between the distance walked at the 6MWT and age, height, final PedsQLTM, forced vital capacity (FVC), and forced expiratory volume in the first second (FEV1), as well as a negative correlation between FEV1/FVC and the distance walked. CONCLUSION: A significant reduction in the quality of life and the functional capacity was observed in children with CKD, influenced by the type of treatment, gender, and sedentary life style. .

OBJETIVOS: Avaliar repercussões da doença renal crônica (DRC) sobre a qualidade de vida na percepção das crianças e dos pais, força muscular respiratória, função pulmonar e capacidade funcional em crianças e adolescentes. MÉTODO: Estudo transversal de crianças e adolescentes com DRC de oito a 17 anos. Excluídas as incapazes de realizar os testes. Após entrevista, aplicou-se questionário de qualidade de vida (PedsQLTM), testes de força muscular, função pulmonar e teste de caminhada de 6 minutos (TC6 min). Foi utilizado o teste t de Student e ANOVA (diferenças de médias) e o coeficiente de correlação de Pearson. Considerou-se nível de significância de 5%. RESULTADOS: Dentre os 40 pacientes, a média da distância percorrida no TC6 min foi de 396 ± 71 metros, e a média do escore final de qualidade de vida percebida pelas crianças e pelos pais de 50,9 e 51, respectivamente. Na percepção das crianças, os transplantados apresentaram maior escore de qualidade de vida, comparados aos em hemodiálise (p < 0,001), e aos com atividade física e melhor qualidade de vida, comparadas às sedentárias (p < 0,001). Na percepção das crianças e dos pais, o sexo masculino apresentou maior escore de qualidade de vida (p < 0,05). Houve correlação positiva entre a distância percorrida no TC6 min e as variáveis idade, altura, PedsQLTM final da criança, capacidade vital forçada (CVF) e volume expiratório forçado no primeiro segundo (VEF1) e negativa entre VEF1/CVF e a distância percorrida. CONCLUSÃO: Observou-se redução significativa na qualidade de vida e na capacidade funcional em crianças com DRC influenciadas pelo tipo de tratamento, sexo e sedentarismo. .

Impact of chronic kidney disease on quality of life, lung function, and functional capacity.

OBJECTIVES: To evaluate the impact of the chronic kidney disease (CKD) on quality of life, from the children's and their parents' perspective, respiratory muscle strength, lung function, and functional capacity in children and adolescents. METHOD: Cross-sectional study of children with CKD aged 8 to 17 years. Those incapable of taking the tests were excluded. After an interview, quality of life by Pediatric Quality of Life Inventory) (PedsQL(TM)), muscular strength, pulmonary function tests, and the 6-minute walking test (6MWT) were applied. Student's t-test, ANOVA (difference in means), and Pearson's coefficient of correlation were used. The level of significance was set at 5%. RESULTS: Of the 40 patients, the mean distance walked at the 6MWT was 396 meters, and the mean final score at the quality of life test as perceived by the children and parents was 50.9 and 51, respectively. From the children's perspective, the transplanted patients had a higher quality of life score when compared to those undergoing hemodialysis (p<0.001); those who practiced physical activity had better quality of life when compared to the sedentary children (p<0.001). From the children's and the parents' perspectives, the male gender had a higher quality of life score (p<0.05). There was a positive correlation between the distance walked at the 6MWT and age, height, final PedsQL(TM), forced vital capacity (FVC), and forced expiratory volume in the first second (FEV1), as well as a negative correlation between FEV1/FVC and the distance walked. CONCLUSION: A significant reduction in the quality of life and the functional capacity was observed in children with CKD, influenced by the type of treatment, gender, and sedentary life style.

Injury of peripheral muscles in smokers with chronic obstructive pulmonary disease.

Muscle injury has clinical relevance in diseased individuals because it is associated with muscle dysfunction in terms of decreased strength and/or endurance. This study was aimed at answering three questions: whether the presence of chronic obstructive pulmonary disease (COPD) is associated with peripheral muscle injury; whether muscle injury is associated with some of the relevant functional impairment in the muscles; and whether muscle injury can be solely justified by deconditioning. Twenty-one male COPD patients were eligible for the study. Seven healthy volunteers recruited from the general population were included as controls. Function of the quadriceps muscle was assessed through specific single-leg exercise (strength and endurance). Cellular (light microscopy) and subcellular (electron microscopy) techniques were used to evaluate muscle injury on biopsies from the vastus lateralis muscle. Signs of injury were found in muscles from both control and COPD patients, not only in cases showing severe airflow obstruction but also in the mild or moderate stages of the disease. Current smoking and presence of COPD were significantly associated with increased injury of the muscle as assessed by light and electron microscopy techniques. The authors conclude that peripheral muscle injury is evident in mild, moderate, and severe stages of COPD even in the absence of respiratory failure, hypercapnia, chronic steroid treatment, low body weight, or some coexisting disease. These findings support the theory that systemic factors with deleterious effect are acting on peripheral muscles of smokers with COPD, increasing the susceptibility of the muscle fibers to membrane and sarcomere injury.

Narrative review: ventilator-induced respiratory muscle weakness.

Clinicians have long been aware that substantial lung injury results when mechanical ventilation imposes too much stress on the pulmonary parenchyma. Evidence is accruing that substantial injury may also result when the ventilator imposes too little stress on the respiratory muscles. Through adjustment of ventilator settings and administration of pharmacotherapy, the respiratory muscles may be rendered almost (or completely) inactive. Research in animals has shown that diaphragmatic inactivity produces severe injury and atrophy of muscle fibers. Human data have recently revealed that 18 to 69 hours of complete diaphragmatic inactivity associated with mechanical ventilation decreased the cross-sectional areas of diaphragmatic fibers by half or more. The atrophic injury seems to result from increased oxidative stress leading to activation of protein-degradation pathways. Scientific understanding of ventilator-induced respiratory muscle injury has not reached the stage where meaningful controlled trials can be done, and thus, it is not possible to give concrete recommendations for patient management. In the meantime, clinicians are advised to select ventilator settings that avoid both excessive patient effort and excessive respiratory muscle rest. The contour of the airway pressure waveform on a ventilator screen provides the most practical indication of patient effort, and clinicians are advised to pay close attention to the waveform as they titrate ventilator settings. Research on ventilator-induced respiratory muscle injury is in its infancy and portends to be an exciting area to follow.

Liga com memória de forma: estudo preliminar do grampo de judet de nitinol e sua possível aplicação em tórax instável / Shape memory alloy: a preliminary study of nitinol judet staples for future application in flail chest

Este artigo sucintamente descreve a evolução da liga metálica “inteligente”, com memória de forma na área de Saúde. A confecção de grampos de Judet em nitinol ocorreu no Laboratório de Transformação Mecânica da UFRGS (LdTM) e a simples verificação das qualidades superelásticas e de memória de forma foram contempladas no LdTM e no HCPA pela equipe envolvida no projeto. A título de ilustração, demonstramos com um caso clínico a aplicabilidade do grampo de Judet no cenário de instabilidade da parede torácica, a qual, além de prejudicar a mecânica respiratória, apresenta uma alta taxa de mortalidade. Os resultados preliminares evidenciaram a transformação provocada pelo calor, ocasionando o fechamento das garras dos grampos de Judet, que se manteve firme e sem alteração da consistência com o tempo, permitindo antever sua aplicabilidade num modelo experimental. Grampos de Judet em Nitinol são apresentados teoricamente como vantajosos em relação aos já existentes em aço inoxidável 316L, especialmente pela facilidade de manuseio e possível simplificação do procedimento cirúrgico. Detalhes no acabamento permitem a biocompatibilidade e o engenheiro projetista de materiais deve compatibilizar as ligas de níquel e titânio (NiTi) utilizadas nos grampos. O nitinol possui amplo emprego no cenário médico-odontológico e há normas técnicas bem definidas. A epidemiologia do trauma e a gravidade das lesões associadas à instabilidade da parede torácica evidenciam a oportunidade de estudos nessa direção. Concluímos sobre a necessidade de prosseguir para uma avaliação experimental, agregando a mensuração de parâmetros viscosos e viscoelásticos da mecânica respiratória, especialmente em seu componente de parede torácica (cw).

The aim of this article is to briefly describe the incorporation of nitinol (NiTi) – an intelligent nickel-titanium alloy presenting shape memory – for use in medical applications. Nitinol Judet staples were developed at the Mechanical Processing Laboratory (LdTM) at Universidade Federal do Rio Grande do Sul. Simple confirmation assays of superelasticity and shape memory were performed at the LdTM and Hospital de Clínicas de Porto Alegre by the project team. A clinical case was used to demonstrate the applicability of nitinol Judet staples in the treatment of flail chest, a condition characterized by respiratory mechanics associated with fairly high mortality. The initial observation revealed a transformation resulting from heat exposure causing the closure of staple prongs. With time, the consistency of the Judet staples remained unchanged, indicating the feasibility of an experimental model employing these staples. The advantages of NiTi-made Judet staples in relation to 316L stainless steel staples are outlined, with emphasis on the ease of use and possible simplification of the surgical procedure. Finishing details ensure biocompatibility, with a focus on specific adaptations in the NiTi alloy employed to manufacture the staples; nevertheless, nitinol is widely employed in medicine and dentistry, with well-defined standards. The epidemiology of trauma and the severity of lesions associated with flail chest provide an opportunity for the proposed studies. The experimental assessment of nitinol Judet staples must now address viscosity and viscoelastic parameters of respiratory mechanics, especially concerning the chest wall.

Respiratory muscle injury, fatigue and serum skeletal troponin I in rat.

To evaluate injury to respiratory muscles of rats breathing against an inspiratory resistive load, we measured the release into blood of a myofilament protein, skeletal troponin I (sTnI), and related this release to the time course of changes in arterial blood gases, respiratory drive (phrenic activity), and pressure generation. After approximately 1.5 h of loading, hypercapnic ventilatory failure occurred, coincident with a decrease in the ratio of transdiaphragmatic pressure to integrated phrenic activity (P(di)/ integral Phr) during sighs. This was followed at approximately 1.9 h by a decrease in the P(di)/ integral Phr ratio during normal loaded breaths (diaphragmatic fatigue). Loading was terminated at pump failure (a decline of P(di) to half of steady-state loaded values), approximately 2.4 h after load onset. During 30 s occlusions post loading, rats generated pressure profiles similar to those during occlusions before loading, with comparable blood gases, but at a higher neural drive. In a second series of rats, we tested for sTnI release using Western blot-direct serum analysis of blood samples taken before and during loading to pump failure. We detected only the fast isoform of sTnI, release beginning midway through loading. Differential detection with various monoclonal antibodies indicated the presence of modified forms of fast sTnI. The release of fast sTnI is consistent with load-induced injury of fast glycolytic fibres of inspiratory muscles, probably the diaphragm. Characterization of released fast sTnI may provide insights into the molecular basis of respiratory muscle dysfunction; fast sTnI may also prove useful as a marker of impending respiratory muscle fatigue.

Respiratory muscle injury: evidence to date and potential mechanisms.

Respiratory muscle dysfunction associated with ventilatory loading may be partially attributed to respiratory muscle injury. Exertion-induced muscle injury can be defined as structural alterations of the muscle, however, a better understanding of the biochemical, morphologic, and functional correlates of injured respiratory muscles will facilitate discrimination of how injury, fatigue, and weakness contribute to respiratory muscle dysfunction. In addition to the increased loads associated with lung disease, many factors such as poor arterial blood gases, immobilization, sepsis, decreased nutrition, and corticosteroids may increase susceptibility to exertion-induced respiratory muscle injury. Respiratory muscle injury in humans is not well-described, however, more extensive evidence has been shown in animal models of increased ventilatory loading. Potential mechanisms of respiratory muscle injury are mechanical stress, metabolic stress, and inflammation. In order to optimize therapeutic interventions, a better understanding of these mechanisms and the patients that are most susceptible to respiratory muscle injury needs to be determined.