Respiratory muscle ultrasonography evaluation and its clinical application in stroke patients: A review

Abstract

Background: Respiratory muscle ultrasound is a widely available, highly feasible technique that can be used to study the contribution of the individual respiratory muscles related to respiratory dysfunction. Stroke disrupts multiple functions, and the respiratory function is often significantly decreased in stroke patients.

Method: A search of the MEDLINE, Web of Science, and PubMed databases was conducted. We identified studies measuring respiratory muscles in healthy and patients by ultrasonography. Two reviewers independently extracted and documented data regarding to the criteria. Data were extracted including participant demographics, ultrasonography evaluation protocol, subject population, reference values, etc.

Result: A total of 1954 participants from 39 studies were included. Among them, there were 1,135 participants from 19 studies on diaphragm, 259 participants from 6 studies on extra-diaphragmatic inspiratory muscles, and 560 participants from 14 studies on abdominal expiratory muscles. The ultrasonic evaluation of diaphragm and abdominal expiratory muscle thickness had a relatively typically approach, while, extra-diaphragmatic inspiratory muscles were mainly used in ICU that lack of a consistent paradigm.

Conclusion: Diaphragm and expiratory muscle ultrasound has been widely used in the assessment of respiratory muscle function. On the contrary, there is not enough evidence to assess extra-diaphragmatic inspiratory muscles by ultrasound. In addition, the thickness of the diaphragm on the hemiplegic side was lower than that on the non-hemiplegic side in stroke patients. For internal oblique muscle (IO), rectus abdominis muscle (RA), transversus abdominis muscle (TrA), and external oblique muscle (EO), most studies showed that the thickness on the hemiplegic side was lower than that on the non-hemiplegic side.Clinical Trial Registration: The protocol of this review was registered in the PROSPERO database (CRD42022352901).

Keywords: diaphragm; evaluation; respiratory muscle; stroke; ultrasonography.

Figure 1

Flow diagram of the review.

Figure 2

Studies for the thickness of the diaphragm ultrasound in stroke patients. The reference values of the diaphragm thickness of the stroke patients at the subacute stage at end-expiration and end-inspiration measured by ultrasound in different studies in Supplementary material 2, presented by the mean ± standard deviation. Where the gray curves (solid and dotted lines) represented the diaphragm thickness at the end of inspiration, and the black curves (solid and dotted lines) were the thickness of the diaphragm at the end of expiration. The solid lines were the thickness of the diaphragm on non-hemiplegic side, while the dotted lines were the hemiplegic side. The values on the abscissa represented the average duration of post-stroke (months).

Figure 3

Studies for the thickness of the expiratory muscle ultrasound in stroke patients. The reference values of the thickness of expiratory muscle at end-expiration measured by ultrasound in different studies in Supplementary material 2, presented by the mean ± standard deviation. Where the solid line was the thickness of the expiratory muscles on non-hemiplegic side, while the dotted line was the hemiplegic side. Labels at the top-right of the abbreviations on the abscissa axis, such as [8],[9],[11], are shown in Supplementary material 2. The abbreviations on the abscissa represented different studies. IO, Internal oblique muscle; EO, External oblique muscle; RA, Rectus abdominis muscle; TrA, Transversus abdominis muscle.