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

 You described how to identify a problem but DID NOTHING TO SOLVE IT. Useless. I'd fire everyone involved for totally missing the only goal in stroke. 100% recovery for all!  Assessments without solutions do nothing for survivor recovery!

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

Xiaoman Liu¹, Ying Yang¹ and Jie Jia^2,3,4*

• ¹Department of Rehabilitation Medicine, The People’s Hospital of Suzhou New District, Suzhou, China
• ²Department of Rehabilitation Medicine, Fudan University Huashan Hospital, Shanghai, China
• ³National Center for Neurological Disorders, Shanghai, China
• ⁴National Clinical Research Center for Aging and Medicine, Fudan University Huashan Hospital, Shanghai, China

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).

1. Introduction

The respiratory muscle pump consists of three primary groups controlling ventilation: the primary muscle of inspiration, the accessory inspiratory, and the expiratory muscles (Shi et al., 2021). The primary muscle of inspiration is the diaphragm, a thin dome-shaped muscle positioned between the chest and abdomen. As the most important respiratory muscle, the diaphragm contributes 60–80% of the ventilation needs of the human body. However, the diaphragm is not the only inspiratory muscle involved in ventilation. When the load imposed on the diaphragm increases, the accessory inspiratory muscles, such as the parasternal intercostal muscles, external intercostal muscles, scalene muscles, and sternocleidomastoid muscles, are recruited to assist in inspiration (Tuinman et al., 2020). With further loading, the expiratory muscles are activated in a fixed hierarchy to assist expiration (Shi et al., 2019). The role of expiratory muscle includes reducing end-expiratory lung volume, reducing transpulmonary pressure, and increasing inspiratory muscle volume (Shi et al., 2019). There are also studies (Dres et al., 2020) showing that the muscle fibers of the parasternal intercostal muscles contract during inspiration, which expands the thoracic cavity, thereby increasing the tidal volume. Generally, during tidal ventilation, the diaphragm works in synergy with the scalene and external intercostal muscles to trigger inspiration, as well as with the dilator muscles of the upper airway. In cases of respiratory distress, the sternocleidomastoid muscles and the trapezius are also recruited (Vivier and Mekontso Dessap, 2020).

Ultrasonography can assess the mechanics, thickness, and strength of all the respiratory muscles (Matamis et al., 2013), and it may be possible to provide valuable information in this context to complement clinical examination. Recent studies proved that ultrasound permits the quantitative assessment of the excursion and thickness of the respiratory muscles to quantify their function (Cala et al., 1998; Sferrazza Papa et al., 2016; Yoshida et al., 2019; Bedewi et al., 2021; Kang et al., 2021). Different ultrasonic techniques have been validated through several studies (Adigozali et al., 2016; Tahan et al., 2016; Bedewi et al., 2021). Stroke disrupts multiple functions (Benditt and Boitano, 2013). The respiratory function is often significantly decreased in stroke patients, and the respiratory intensity is only about 50% of the normal population. The respiratory dysfunction can be attributed to the affected respiratory central nervous system and respiratory muscles (Rochester and Mohsenin, 2002; Jandt et al., 2011). In this context, the present review has two objectives. The first is to review the ultrasound assessment of respiratory muscles. The second objective is the clinical application of respiratory muscle ultrasound in stroke patients.

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