Case Studies in Physiology: Physiological and clinical effects of temporary diaphragm pacing in two patients with ventilator-induced diaphragm dysfunction.

Ventilator-induced diaphragm dysfunction (VIDD) is increasingly recognized as an important side-effect of invasive ventilation in critically ill patients and is associated with poor outcomes. Whether patients with VIDD benefit from temporary diaphragm pacing is uncertain. Intramuscular diaphragmatic electrodes were implanted for temporary stimulation with a pacing device (TransAeris System) in two patients with VIDD. The electrodes were implanted via laparoscopy (first patient) or via bilateral thoracoscopy (second patient). Stimulation parameters were titrated according to tolerance. Diaphragm thickening fraction by ultrasound, maximum inspiratory pressure (Pimax) and diaphragm electromyography (EMGdi) signal analysis were used to monitor the response to diaphragm pacing. Both patients tolerated diaphragm pacing. In the first patient, improvements in diaphragm excursions were noted once pacing was initiated and diaphragm thickening fraction did not further deteriorate over time. The diaphragm thickening fraction improved in the second patient, and Pimax as well as EMGdi analysis suggested improved muscle function. This patient could be fully weaned from the ventilator. These case reports present the first experience with temporary diaphragm pacing in critically ill patients with VIDD. Our results should be taken cautiously given the reduced sample size, but provide the proof of concept to put forward the hypothesis that a course of diaphragm pacing may be associated with improved diaphragmatic function. Our findings of the tolerance to the procedure and the beneficial physiological effects are not prove of safety and efficacy, but may set the ground to design and conduct larger studies.NEW & NOTEWORTHY Diaphragmatic electrode implantation and temporary diaphragm pacing have not been previously used in ICU patients with VIDD. Patients were monitored using a multimodal monitoring approach including ultrasound of the diaphragm, measurement of maximum inspiratory pressure and EMG signal analysis. Our results suggest that diaphragm pacing may improve diaphragmatic function, with the potential to prevent and treat VIDD in critically ill patients. Safety and efficacy of this intervention is yet to be proven in larger studies.

High-flow nasal cannula for Acute Respiratory Distress Syndrome (ARDS) due to COVID-19.

INTRODUCTION: High-flow nasal cannula oxygen therapy (HFNC) has been shown to be a useful therapy in the treatment of patients with Acute Respiratory Distress Syndrome (ARDS), but its efficacy is still unknown in patients with COVID-19. Our objective is to describe its utility as therapy for the treatment of ARDS caused by SARS-CoV-2. METHODS: A retrospective, observational study was performed at a single centre, evaluating patients with ARDS secondary to COVID-19 treated with HFNC. The main outcome was the intubation rate at day 30, which defined failure of therapy. We also analysed the role of the ROX index to predict the need for intubation. RESULTS: In the study period, 196 patients with bilateral pneumonia were admitted to our pulmonology unit, 40 of whom were treated with HFNC due to the presence of ARDS. The intubation rate at day 30 was 52.5%, and overall mortality was 22.5%. After initiating HFNC, the SpO2/FiO2 ratio was significantly better in the group that did not require intubation (113.4±6.6 vs 93.7±6.7, p=0.020), as was the ROX index (5.0±1.6 vs 4.0±1.0, p=0.018). A ROX index less than 4.94 measured 2 to 6 h after the start of therapy was associated with increased risk of intubation (HR 4.03 [95% CI 1.18 - 13.7]; p=0.026). CONCLUSION: High-flow therapy is a useful treatment in ARDS in order to avoid intubation or as a bridge therapy, and no increased mortality was observed secondary to the delay in intubation. After initiating HFNC, a ROX index below 4.94 predicts the need for intubation.