Diaphragmatic Ultrasound and Chest Wall Excursion Measurements in Predicting Ventilator Weaning Success amongst Pediatric Neurorehabilitation Inpatients: A Retrospective Case Series

Background and Purpose Prompt transfer of medically stable pediatric patients with neurologic diagnoses to the inpatient rehabilitation unit is desirable to address their functional recovery. However, there is limited data on how to prioritize the need for intensive rehabilitation in the presence of ongoing need for mechanical ventilator support, outside the intensive care unit setting. This is especially true for patients who may be candidates for ventilator weaning. This dilemma involves choosing between a facility that primarily focuses on ventilator weaning, such as a long-term acute care hospital, or an inpatient rehabilitation facility that offers greater rehabilitation services but lacks evidence-based guidelines for approaching ventilator weaning in this setting. To address this challenge, this study explores the potential of leveraging inpatient rehabilitation expertise in bedside assessments of respiratory muscle function, specifically using point-of-care diaphragm ultrasound as a promising tool to guide ventilator weaning in the inpatient rehabilitation setting. Methods This is a retrospective case series conducted at a university-affiliated, freestanding acute rehabilitation hospital. We performed a retrospective chart review of pediatric patients (n=17) within this setting who, because of neurological injury or disease, relied on invasive mechanical ventilator support via tracheostomy. Patient characteristics including primary rehabilitation diagnosis were recorded, along with number of hours per day the patient relied on mechanical ventilator support at admission and then at discharge from inpatient rehabilitation hospital. Routinely performed assessments of respiratory muscle function at our facility included three modalities: (i) diaphragm muscle ultrasound B-mode measurements; (ii) inspiratory excursion measurements which measure the expansion of the chest and abdominal wall at specific sites during both tidal volume and vital capacity breaths; and (iii) pulmonary function measures - vital capacity and negative inspiratory force. The primary focus was the length of time that the patient achieved ventilator free breathing at the time of discharge from the acute rehabilitation setting. Results We included 17 patients (age 5-18 years old), all who required full support of mechanical ventilator upon admission to inpatient rehabilitation hospital. Upon discharge, 13 of these patients were either fully or partially weaned (nocturnal ventilator use only) from invasive mechanical ventilator support. Ultrasound determined diaphragm muscle thickening ratio was the assessment most predictive of ventilator weaning outcome. Specifically, all patients with at least one hemidiaphragm that had a thickening ratio ≥1.2 achieved some degree of ventilator weaning during inpatient rehabilitation stay. Conclusion For the pediatric inpatient rehabilitation population that utilizes invasive mechanical ventilation because of neurological injury or disease, ultrasound determined diaphragm muscle thickening appears to serve as a useful tool for guiding ventilator management. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was funded, in part, by Stephany Kunzweilers Project Grant via the Catalyst Grant Program of the Shirley Ryan AbilityLab rehabilitation hospital. Colin Franz would like to acknowledge funding for this project from the Belle Carnell Regenerative Neurorehabilitation fund. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All patients had failed ventilator weaning at their previous acute care or long-term acute care settings. Study approval was obtained by the Northwestern Institutional Review Board (STU00211466). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors.