Ultrasonographic Assessment of Diaphragm Function in Critically Ill Subjects

Abstract

The majority of patients admitted to the ICU require mechanical ventilation as a part of their process of care. However, mechanical ventilation itself or the underlying disease can lead to dysfunction of the diaphragm, a condition that may contribute to the failure of weaning from mechanical ventilation. However, extended time on the ventilator increases health-care costs and greatly increases patient morbidity and mortality. Nevertheless, symptoms and signs of muscle disease in a bedridden (or bed rest-only) ICU patient are often difficult to assess because of concomitant confounding factors. Conventional assessment of diaphragm function lacks specific, noninvasive, time-saving, and easily performed bedside tools or requires patient cooperation. Recently, the use of ultrasound has raised great interest as a simple, noninvasive method of quantification of diaphragm contractile activity. In this review, we discuss the physiology and the relevant pathophysiology of diaphragm function, and we summarize the recent findings concerning the evaluation of its (dys)function in critically ill patients, with a special focus on the role of ultrasounds. We describe how to assess diaphragm excursion and diaphragm thickening during breathing and the meaning of these measurements under spontaneous or mechanical ventilation as well as the reference values in health and disease. The spread of ultrasonographic assessment of diaphragm function may possibly result in timely identification of patients with diaphragm dysfunction and to a potential improvement in the assessment of recovery from diaphragm weakness.

A prospective observational study on critically ill children with diaphragmatic dysfunction: clinical outcomes and risk factors

“…Third, the average time for ventilatory treatment was more the elderly than that in the children with DD [576 (374-850) hrs vs360 (168-528)] [8,25] . In addition, in critically ill children, we observed that the time of ventilation is a risk factor independent of DD, similar to that observed in adult studies [2,30] . Further, the association of elevated CRP with DD development is another important observation in this study.…”

Neuromuscular Ultrasound: Clinical Applications and Diagnostic Values

“…In contrast to evaluating ICU-acquired weakness, ultrasound is an ideal non-invasive bedside procedure for the detection of early neuromuscular diaphragmatic dysfunction of any cause, with a sensitivity of 93% and a specificity of 100%. 70,71 Biomarker for Treatment Trials A longitudinal observational study of 18 boys with DMD showed high correlations of increasing muscle echogenicity with disease progression and functional status. 11 As well, among 5 young boys (age 0.5-2.8 years) with DMD, there was evidence of disease progression with increased muscle EI over 2.5 years, despite functional improvements during early childhood; 72 quantitative muscle ultrasound by backscatter or grayscale analysis from superficial regions of muscles provided comparable measures of disease pathology in this population.…”

Body Position Affects Ultrasonographic Measurement of Diaphragm Contractility

“…This is despite the emergence of using diaphragm ultrasound imaging to quantify its motion or muscle contractility during the ICU admission. 21 – 23 This imaging modality has shown broad applicability in the ICU, 24 – 39 and demonstrated strong methodological properties. 24 , 31 – 33 , 37 , 40 It may be applied repeatedly at bedside 23 , 27 , 34 , 37 while avoiding the exposure to ionizing radiation associated with conventional radiographs or fluoroscopy.…”

“… 24 , 31 – 33 , 37 , 40 It may be applied repeatedly at bedside 23 , 27 , 34 , 37 while avoiding the exposure to ionizing radiation associated with conventional radiographs or fluoroscopy. 21 – 23 , 30 In addition, it negates the impracticality of transporting critically ill patients for computed tomography or magnetic resonance imaging. 21 , 30 Successful training programs for novice diaphragm ultrasonographers have been reportedly brief, 24 , 33 , 41 , 42 suggesting accessibility to PTs working in the ICU.…”

“… 21 – 23 , 30 In addition, it negates the impracticality of transporting critically ill patients for computed tomography or magnetic resonance imaging. 21 , 30 Successful training programs for novice diaphragm ultrasonographers have been reportedly brief, 24 , 33 , 41 , 42 suggesting accessibility to PTs working in the ICU.…”