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INTRODUCTION/AIMS: Diaphragm ultrasound is increasingly used in the diagnosis of diaphragm dysfunction and to guide respiratory management in patients with neuromuscular disorders and those who are critically ill. However, the association between diaphragm ultrasound variables and demographic factors like age, sex, and body mass index (BMI) are understudied. Such relationships are important for correct interpretation of normative values and comparison with selected patients groups. The aim of this study was to determine the associations between diaphragm ultrasound variables and subject characteristics. METHODS: B-mode ultrasound was used to image the diaphragm at the zone of apposition in 83 healthy subjects. Diaphragm thickness at resting end-expiration (Tend-exp ), diaphragm thickness at maximal end-inspiration (Tmax-insp ), diaphragm thickening ratio (Tmax-insp /Tend-exp ), and diaphragm echogenicity were measured. Multivariate linear regression was used to explore the associations between diaphragm ultrasound variables and subject characteristics. RESULTS: Tend-exp , Tmax-insp , and thickening ratio do not change with age whereas diaphragm echogenicity increases with age. The thickening ratio had a weak negative association with BMI, while Tend-exp was positively associated with BMI. Men had a larger Tend-exp and Tmax-insp than women (Tend-exp 1.6 ± 0.5 and 1.4 ± 0.3 mm; p = .011, Tmax-insp 3.8 ± 1.0 and 3.2 ± 0.9 mm; p = .004), but similar thickening ratios. DISCUSSION: Diaphragm thickness, thickening, and echogenicity measured with ultrasound are associated with factors such as age, BMI, and sex. Therefore, subject characteristics should be considered when interpreting diaphragm ultrasound measurements. In the absence of normative values, matched control groups are a prerequisite for research and in clinical practice.
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Índice de Massa Corporal , Diafragma , Ultrassonografia , Fatores Etários , Diafragma/diagnóstico por imagem , Diafragma/fisiologia , Feminino , Voluntários Saudáveis , Humanos , Masculino , Respiração , Fatores Sexuais , Ultrassonografia/métodosRESUMO
Respiratory muscle weakness is common in neuromuscular disorders (NMDs) and leads to significant respiratory difficulties. Therefore, reliable and easy assessment of respiratory muscle structure and function in NMDs is crucial. In the last decade, ultrasound and magnetic resonance imaging (MRI) have emerged as promising imaging techniques to assess respiratory muscle structure and function. Respiratory muscle imaging directly measures the respiratory muscles and, in contrast to pulmonary function testing, is independent of patient effort. This makes respiratory muscle imaging suitable to use as a tool in clinical respiratory management and as an outcome parameter in upcoming drug trials for NMDs, particularly in children. In this narrative review, we discuss the latest studies and technological developments in imaging of the respiratory muscles by ultrasound and MRI, and its clinical application and limitations. We aim to increase understanding of respiratory muscle imaging and facilitate its use as an outcome measure in daily practice and clinical trials.
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Doenças Neuromusculares , Músculos Respiratórios , Criança , Humanos , Imageamento por Ressonância Magnética , Debilidade Muscular , Doenças Neuromusculares/diagnóstico por imagem , UltrassonografiaRESUMO
INTRODUCTION: LAMA2-related muscular dystrophy (LAMA2-MD) and SELENON(SEPN1)-related congenital myopathy (SELENON-RM) are rare neuromuscular diseases with respiratory impairment from a young age. Prospective natural history studies are needed for prevalence estimations, respiratory characterization, optimizing clinical care and selecting outcome measures for trial readiness. METHODS: Our prospective 1.5-year natural history study included spirometry (forced vital capacity (FVC); difference between upright and supine vital capacity (dVC)), respiratory muscle strength tests (sniff nasal inspiratory pressure (SNIP)) (age≥5 years), and diaphragm ultrasound (thickness; thickening; echogenicity; all ages). RESULTS: Twenty-six LAMA2-MD patients (M = 8, median 21 [9; 31] years) and 11 SELENON-RM patients (M = 8, 20 [10; 33] years) were included. At baseline, 17 (85 %) LAMA2-MD (FVC%: 59 % [33; 68]) and all SELENON-RM patients (FVC%: 34 % [31; 46]) had an impaired respiratory function (FVC%<80 %). Nine (35 %) LAMA2-MD and eight (73 %) SELENON-RM patients received mechanical ventilation at baseline, and two additional SELENON-RM patients started during follow-up. Contrarily to LAMA2-MD, SELENON-RM patients had severe diaphragm atrophy (diaphragm thickness z-score: 2.5 [-3.1; -2.1]) and dysfunction (diaphragm thickness ratio: 1.2 [1.0; 1.7]; dVC: 30 % [7.7; 41]). SNIP was low in both neuromuscular diseases and correlated with motor function. In SELENON-RM, respiratory function decreased during follow-up. CONCLUSION: The majority of LAMA2-MD and all SELENON-RM patients had respiratory impairment. SELENON-RM patients showed lower respiratory function which was progressive, more prevalent mechanical ventilation, and more severe diaphragm atrophy and dysfunction than LAMA2-MD patients. Spirometry (FVC%, dVC) and respiratory muscle strength tests (SNIP) are useful in clinical care and as outcome measure in clinical trials. CLINICAL TRIAL NUMBER: NCT04478981.
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Doenças Musculares , Distrofias Musculares , Doenças Neuromusculares , Insuficiência Respiratória , Humanos , Pré-Escolar , Estudos Prospectivos , Músculos Respiratórios , Insuficiência Respiratória/etiologia , AtrofiaRESUMO
Prolonged air leakage (AL) following pulmonary resections leads to prolonged hospital stay and post-operative complications. Intra- and postoperative quantification of AL might be useful for improving treatment decisions, but these measurements have not been characterised. AL calculations based on inspiratory and expiratory tidal volumes were investigated in an Intensive Care Unit mechanical ventilator circuit (Servo-I). AL was also measured by a digital chest drainage system. This study shows that AL measurements increase in accuracy when corrected for baseline deviations (R: 0.904 > 0.997, p < 0.001). Bland-Altman analysis revealed a funnel-shape, indicative of a detection threshhold. Corrected measurements were most accurate when averaged over five breaths and AL was >500 mL/min, with an estimated mean systemic bias of 7.4% (95%-limits of agreement [LoA]: 1.1%-13.7%) at 500 mL/min air leak. Breath-by-breath analysis showed most accurate results at AL >20 mL/breath (R: 0.989-0.991, p < 0.001) at tidal volumes between 350-600 mL. The digital drain had a mean systemic bias of -11.1% (95%-LoA: -18.9% to -3.3%) with homogenous scatter in Bland-Altman analysis and a strong correlation to the control measurement over a large range (0-2000mL/min, R: 0.999, p < 0.001). This study indicates that the Servo-I can be used for air leak quantification in clinically relevant ranges (>500 mL/min), but is unsuited for small leak detection due to a detection threshold. Researchers and clinicians should be aware of varying accuracy and interoperability characteristics between AL measurement devices.
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In this cross-sectional study, we comprehensively assessed respiratory muscle function in various clinical forms of nemaline myopathy (NM) including non-volitional tests for diaphragm function. Forty-two patients with NM were included (10 males (25-74 y/o); 32 females (11-76 y/o)). The NM forms were typical (n=11), mild (n=7), or childhood-onset with slowness of movements (n=24). Forced vital capacity (FVC) and maximal inspiratory pressure were decreased in typical NM in comparison with childhood-onset NM with slowness (32.0 [29.0-58.5] vs 81.0 [75.0-87.0]%, p<0.01, and 35.0 [24.0-55.0] vs 81.0 [65.0-102.5] cmH2O, p<0.01). Eight patients with childhood-onset NM with slowness had respiratory muscle weakness. There was a low correlation between FVC and Motor Function Measure scores (r=0.48, p<0.01). End-inspiratory diaphragm thickness and twitch mouth pressure were decreased in patients requiring home mechanical ventilation compared to non-ventilated patients with normal lung function (1.8 [1.5-2.4] vs 3.1 [2.0-4.6] mm, p=0.049, and -7.9 [-10.9- -4.0] vs -14.9 [-17.3- -12.6], p=0.04). Our results show that respiratory muscle weakness is present in all NM forms, including childhood-onset NM with slowness, and may be present irrespective of the degree of general motor function impairment. These findings highlight the importance for screening of respiratory function in patients with NM to guide respiratory management.