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

ABSTRACT 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.