American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Oct 2020
MRI Evaluation of Regional Lung Tidal Volumes in Severe Neonatal Bronchopulmonary Dysplasia.
Rationale: Bronchopulmonary dysplasia is a heterogeneous lung disease characterized by regions of cysts and fibrosis, but methods for evaluating lung function are limited to whole lung rather than specific regions of interest. Objectives: Respiratory-gated, ultrashort echo time magnetic resonance imaging was used to test the hypothesis that cystic regions of the lung will exhibit a quantifiable Vt that will correlate with ventilator settings and clinical outcomes. Methods: Magnetic resonance images of 17 nonsedated, quiet-breathing infants with severe bronchopulmonary dysplasia were reconstructed into end-inspiration and end-expiration images. ⋯ Inspiratory time and respiratory rate did not improve Vt of any analyzed lung region. Conclusions: Cystic lung has greater normalized Vt when compared with noncystic lung. Ventilator pressure increases noncystic lung Vt, but inspiratory time does not correlate with Vt of normal or cystic lung.
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Am. J. Respir. Crit. Care Med. · Oct 2020
Tissue Doppler Imaging of the Diaphragm in Healthy Subjects and Critically Ill Patients.
Rationale: Tissue Doppler imaging (TDI) is an echocardiographic method that measures the velocity of moving tissue. Objectives: We applied this technique to the diaphragm to assess the velocity of diaphragmatic muscle motion during contraction and relaxation. Methods: In 20 healthy volunteers, diaphragmatic TDI was performed to assess the pattern of diaphragmatic motion velocity, measure its normal values, and determine the intra- and interobserver variability of measurements. ⋯ Peak contraction velocity was strongly correlated with peak transdiaphragmatic pressure and pressure-time product, whereas Pdi-maximal relaxation rate was significantly correlated with TDI-maximal relaxation rate. Conclusions: Diaphragmatic tissue Doppler allows real-time assessment of the diaphragmatic tissue motion velocity. Diaphragmatic TDI-derived parameters differentiate patients who fail a weaning trial from those who succeed and correlate well with Pdi-derived parameters.