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Ultrasound and non-ultrasound imaging techniques in the assessment of diaphragmatic dysfunction

ABSTRACT: Diaphragm muscle dysfunction is increasingly recognized as an important element of several diseases including neuromuscular disease, chronic obstructive pulmonary disease and diaphragm dysfunction in critically ill patients. Functional evaluation of the diaphragm is challenging. Use of volitional maneuvers to test the diaphragm can be limited by patient effort. Non-volitional tests such as those using neuromuscular stimulation are technically complex, since the muscle itself is relatively inaccessible. As such, there is a growing interest in using imaging techniques to characterize diaphragm muscle dysfunction. Selecting the appropriate imaging technique for a given clinical scenario is a critical step in the evaluation of patients suspected of having diaphragm dysfunction. In this review, we aim to present a detailed analysis of evidence for the use of ultrasound and non-ultrasound imaging techniques in the assessment of diaphragm dysfunction. We highlight the utility of the qualitative information gathered by ultrasound imaging as a means to assess integrity, excursion, thickness, and thickening of the diaphragm. In contrast, quantitative ultrasound analysis of the diaphragm is marred by inherent limitations of this technique, and we provide a detailed examination of these limitations. We evaluate non-ultrasound imaging modalities that apply static techniques (chest radiograph, computerized tomography and magnetic resonance imaging), used to assess muscle position, shape and dimension. We also evaluate non-ultrasound imaging modalities that apply dynamic imaging (fluoroscopy and dynamic magnetic resonance imaging) to assess diaphragm motion. Finally, we critically review the application of each of these techniques in the clinical setting when diaphragm dysfunction is suspected.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01441-6.

SUBMITTER: Laghi F

PROVIDER: S-EPMC7958108 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Project description:Although diaphragmatic dysfunction is an important indicator of severity of illness and poor prognosis in ICU patients, there is no convenient and practical method to monitor diaphragmatic function. This study was designed to analyze diaphragmatic dynamic dysfunction by bedside ultrasound in septic patients and provide quantitative evidence to assess diaphragm function systematically. This prospective observational study was conducted from October 2019 to January 2021 in the Department of Respiratory and Critical Care Medicine. 74 patients suffered from sepsis were recruited and divided into two groups, sepsis group 1 (2 ≤ SOFA ≤ 5, n = 41) and sepsis group 2 (SOFA > 5, n = 33). 107 healthy volunteers were randomly recruited as the control group. In all participants, the diaphragmatic thickness and excursion were measured directly and the dynamic parameters including thickening fraction (TF), EQB/EDB, Contractile velocity, and area under diaphragmatic movement curve (AUDMC) were calculated by bedside ultrasound during quiet breathing (QB) and deep breathing (DB). Each parameter among three groups was analyzed separately by covariance analysis, which was adjusted by age, sex, body mass index, MAP, hypertension, and diabetes. First, contractile dysfunction occurred before diaphragmatic atrophy both in sepsis group 1 and sepsis group 2. Second, compared with the control group, the dynamic parameters showed significant decrease in sepsis group 1 and more obvious change in sepsis group 2, including TF, EQB/EDB. Third, the maximum contractile velocity decreased in sepsis group 1, reflecting the damage of intrinsic contraction efficiency accurately. Finally, per breathing AUDMC in two septic groups were lower than those in control group. However, per minute AUDMC was compensated by increasing respiratory rate in sepsis group 1, whereas it failed to be compensated which indicated gradual failure of diaphragm in sepsis group 2. Diaphragmatic ultrasound can be used to quantitatively evaluate the severity of sepsis patients whose contractile dysfunction occurred before diaphragmatic atrophy. As dynamic parameters, TF and EQB/EDB are early indicator associated with diaphragmatic injury. Furthermore, maximum contractile velocity can reflect intrinsic contraction efficiency accurately. AUDMC can evaluate diaphragmatic breathing effort and endurance to overcome resistance loads effectively.

Project description:(1) Background: Technically, a simple, inexpensive, and non-invasive method of ascertaining volume changes in thoracic and abdominal cavities are required to expedite the development and validation of pulmonary mechanics models. Clinically, this measure enables the real-time monitoring of muscular recruitment patterns and breathing effort. Thus, it has the potential, for example, to help differentiate between respiratory disease and dysfunctional breathing, which otherwise can present with similar symptoms such as breath rate. Current automatic methods of measuring chest expansion are invasive, intrusive, and/or difficult to conduct in conjunction with pulmonary function testing (spontaneous breathing pressure and flow measurements). (2) Methods: A tape measure and rotary encoder band system developed by the authors was used to directly measure changes in thoracic and abdominal circumferences without the calibration required for analogous strain-gauge-based or image processing solutions. (3) Results: Using scaling factors from the literature allowed for the conversion of thoracic and abdominal motion to lung volume, combining motion measurements correlated to flow-based measured tidal volume (normalised by subject weight) with R2 = 0.79 in data from 29 healthy adult subjects during panting, normal, and deep breathing at 0 cmH2O (ZEEP), 4 cmH2O, and 8 cmH2O PEEP (positive end-expiratory pressure). However, the correlation for individual subjects is substantially higher, indicating size and other physiological differences should be accounted for in scaling. The pattern of abdominal and chest expansion was captured, allowing for the analysis of muscular recruitment patterns over different breathing modes and the differentiation of active and passive modes. (4) Conclusions: The method and measuring device(s) enable the validation of patient-specific lung mechanics models and accurately elucidate diaphragmatic-driven volume changes due to intercostal/chest-wall muscular recruitment and elastic recoil.

Project description:Background:Although non-invasive mechanical ventilation (NIV) is the gold standard treatment for patients with acute exacerbation of COPD (AECOPD) developing respiratory acidosis, failure rates still range from 5% to 40%. Recent studies have shown that the onset of severe diaphragmatic dysfunction (DD) during AECOPD increases risk of NIV failure and mortality in this subset of patients. Although the imbalance between the load and the contractile capacity of inspiratory muscles seems the main cause of AECOPD-induced hypercapnic respiratory failure, data regarding the influence of mechanical derangement on DD in this acute phase are lacking. With this study, we investigate the impact of respiratory mechanics on diaphragm function in AECOPD patients experiencing NIV failure. Methods:Twelve AECOPD patients with respiratory acidosis admitted to the Respiratory ICU of the University Hospital of Modena from 2017 to 2018 undergoing mechanical ventilation (MV) due to NIV failure were enrolled. Static respiratory mechanics and end-expiratory lung volume (EELV) were measured after 30 mins of volume control mode MV. Subsequently, transdiaphragmatic pressure (Pdi) was calculated by means of a sniff maneuver (Pdisniff) after 30 mins of spontaneous breathing trial. Linear regression analysis and Pearson's correlation coefficient served to assess associations. Results:Average Pdisniff was 23.3 cmH2O (standard deviation 29 cmH2O) with 3 patients presenting bilateral diaphragm palsy. Pdisniff was directly correlated with static lung elastance (r=0.69, p=0.001) while inverse correlation was found with dynamic intrinsic PEEP (r=-0.73, p=0.007). No significant correlation was found with static intrinsic PEEP (r=-0.55, p=0.06), EELV (r=-0.4, p=0.3), airway resistance (r=-0.2, p=0.54), chest wall, and total elastance (r=-0-01, p=0.96 and r=0.3, p=0.36, respectively). Significant linear inverse correlation was found between Pdisniff and the ratio between Pdi assessed at tidal volume and Pdi sniff (r=-0.82, p=0.02). Conclusion:The causes of extreme DD in AECOPD patients who experienced NIV failure might be predominantly mechanical, driven by a severe dynamic hyperinflation that overlaps on an elastic lung substrate favoring volume overload.

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Ultrasound and non-ultrasound imaging techniques in the assessment of diaphragmatic dysfunction

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