Weaning failure from mechanical ventilation: a scoping review of the utility of ultrasonography in the weaning process

Abstract

Background: Weaning failure has been associated with increased hospital stay and higher mortality. Identification of the risk factors that may affect weaning outcome is paramount. Ultrasonography is an excellent tool for pulmonary and diaphragmatic monitoring during mechanical ventilation, allowing real-time evaluation of anatomical structures and function. We performed a scoping review to highlight the usefulness and limitations of ultrasonography as a tool for detecting weaning failure.

Methods: The Joanna Briggs Institute recommendations, the PRISMA Extension for Scoping Reviews (PRISMA-ScR) checklist, and the methodological framework by Arksey and O'Malley were followed. We searched PubMed, Scopus, and Cochrane databases for observational and randomised studies published from inception to August 12, 2024. Inclusion criteria were articles written in English, intensive care unit setting, mechanical ventilation, adults, and those that described a measure for burden of weaning failure using ultrasonography.

Results: The search revealed 3573 records. After removal of duplicates, 3117 articles were screened for potential inclusion, of which 89 articles were finally included. These comprised six clinical trials, 80 observational prospective studies, and three retrospective studies. In total, 6841 subjects were included, with a weaning failure rate of 28.2%. The parameters most associated with weaning failure were higher ratio of early diastolic mitral inflow velocity to early diastolic septal mitral annulus velocity, diaphragmatic excursion, diaphragm thickening fraction, diaphragmatic rapid shallow breathing index, ratio between ventilatory frequency, diaphragmatic displacement, excursions, and contraction velocity on coughing. Loss of aeration, pulmonary oedema, and pleural effusion detected with ultrasound were associated with weaning failure and airway obstruction caused by post-extubation laryngeal oedema.

Conclusions: Ultrasound represents a valuable tool for optimising the weaning process. It enables precise assessment of lung function and diaphragmatic performance, underscoring the need for its implementation in ICU setting.

Keywords: critical care; extubation; intensive care; mechanical ventilation; post-extubation failure; ultrasonography; weaning.

Fig 1

PRISMA flow-chart of inclusion. From Page MJ, McKenzie JE, Bossuyt PM et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021; 372: n71.

Fig 2

Five key steps of ultrasonography in weaning from mechanical ventilation. This figure shows the main domains identified by lung ultrasound to facilitate clinical decision-making in weaning process. LUS, lung ultrasound score; SBT, spontaneous breathing test; WIPO, weaning-induced pulmonary oedema; X-Ray, radiography.

Fig 3

Proposed algorithm to integrate ultrasonography in the weaning process. This figure presents a possible algorithm for integrating ultrasound into the weaning process. CPAP, continuous positive airway pressure; IWI, integrative weaning index; NIF, negative inspiratory force; NIV, noninvasive ventilation; PSV, pressure support ventilation; RSBI, rapid shallow breathing index.

Fig 4

Diaphragmatic thickening. Ultrasonographic evaluation revealed diaphragmatic atrophy, observing a decrease in diaphragm thickness during expiration (0.09 cm; normal value: 0.13–0.15 cm), and a thickening fraction of 31.6%. Diaphragmatic thickening is seen with a 7.5–10 MHz linear probe at the level of the apposition zone. The end-expiratory thickness in expiration was 19 mm, whereas the end-inspiratory thickness in inspiration was 25 mm. The thickening fraction corresponded to: TF=(25–19)/19×100=31.6%.

Fig 5

Consolidation and pleural effusion at lung ultrasound. The right lung base is seen with a convex probe. (a) Consolidation pattern with air bronchogram (indicated with arrow). (b) After 3 days, an improvement in lung ventilation is seen without consolidation pattern. (c) With convex probe in transverse plane at anterior level, B-lines of interstitial type secondary to weaning-induced pulmonary oedema (WIPO) are displayed. (d) With a convex probe in transverse position, perpendicular to the chest wall, at the level of the right base, extensive pleural effusion is seen. According to Balik's formula, a volume of 720 ml is estimated. Measuring the maximum separation between parietal and visceral pleural at maximal inspiration: 36 mm×20=720 ml.

Fig 6

Airway obstruction as a result of laryngeal oedema. Ultrasound with linear probe, in transverse plane at the level of the thyroid cartilage. (a and b) A decrease in space between both vocal folds secondary to laryngeal oedema is seen. Green: thyroid cartilage; orange: vocal folds; purple: arytenoid cartilage. (c) Real image through video laryngoscopy during reintubation where the laryngeal oedema is seen.