Physiological Effects of High-Flow Tracheal Oxygen in Tracheostomized Patients Weaning From Mechanical Ventilation.

BACKGROUND: High-flow tracheal oxygen (HFTO) is being used as supportive therapy during weaning in tracheostomized patients difficult to wean from invasive mechanical ventilation. There is, however, no clinical evidence for such a strategy. Therefore, we conducted a systematic review to summarize studies evaluating the physiologic effects of HFTO during tracheostomy-facilitated weaning and to identify potential areas for future research in this field. METHODS: Observational and interventional studies on critically ill subjects weaning from mechanical ventilation via tracheostomy published until December 22, 2022, were eligible. Studies on high-flow oxygen, only in children, non-human models or animals, on clinical outcome only, abstracts without full-text availability, case reports, and reviews were excluded. Main outcomes were end-expiratory lung volume (EELV) and tidal volume using electrical impedance tomography, respiratory effort assessed by esophageal manometry, work of breathing and neuroventilatory drive as assessed by electrical activity of the diaphragm (EAdi) signal, airway pressure (Paw), oxygenation (PaO2 /FIO2 or SpO2 /FIO2 ), breathing frequency, tidal volume, and PaCO2 . RESULTS: In total, 1,327 references were identified, of which 5 were included. In all studies, HFTO was administered with flow 50 L/min and compared to conventional O2 therapy in a crossover design. The total average duration of invasive ventilation at time of measurements ranged from 11-27 d. In two studies, PaO2 /FIO2 and mean Paw were higher with HFTO. EELV, tidal volumes, esophageal pressure swings, and EAdi were similar during high-flow tracheal oxygen and conventional O2 therapy. CONCLUSIONS: The main physiological effect of HFTO as compared to conventional O2 therapy in tracheostomized subjects weaning from mechanical ventilation was improved oxygenation that is probably flow-dependent. Respiratory effort, lung aeration, neuroventilatory drive, and ventilation were similar for HFTO and conventional O2 therapy. Future studies on HFTO should be performed early in the weaning process and should evaluate its effect on sputum clearance and patient-centered outcomes like dyspnea.

Electrical Impedance Tomography As a Bedside Diagnostic Tool for Pulmonary Embolism.

Electrical impedance tomography (EIT) has been shown to be of value in evaluating the distribution of ventilation. In addition, several studies, particularly case reports, have demonstrated the use of EIT in the assessment of lung perfusion. EIT may be a potential diagnostic bedside tool in the diagnosis and follow-up of acute pulmonary embolism. CASE SUMMARY: We present one case of a patient with COVID-19 who likely had pulmonary thromboembolism where perfusion scans were made before and after thrombolytic therapy. Perfusion scans showed improvement after thrombolytic therapy. This article should therefore be seen as a first step in proving the validity of EIT-derived perfusion scans as a diagnostic for pulmonary embolism. CONCLUSION: The hypertonic saline bolus EIT method as a diagnostic tool for pulmonary embolism is a promising new technique, which can be particularly meaningful for critically ill patients. Further study is required to evaluate the sensitivity and specificity of this technique and the impact on decision-making and outcomes of critically ill patients.

High-flow Nasal Cannula therapy: A feasible treatment for vulnerable elderly COVID-19 patients in the wards.

BACKGROUND: Invasive mechanical ventilation is the treatment of choice in COVID-19 patients when hypoxemia persists, despite maximum conventional oxygen administration. Some frail patients with severe hypoxemic respiratory failure are deemed not eligible for invasive mechanical ventilation. OBJECTIVES: To investigate whether High-flow nasal cannula (HFNC) in the wards could serve as a rescue therapy in these frail patients. METHODS: This retrospective cohort study included frail COVID-19 patients admitted to the hospital between March 9th and May 1st 2020. HFNC therapy was started in the wards. The primary endpoint was the survival rate at hospital discharge. RESULTS: Thirty-two patients with a median age of 79.0 years (74.5-83.0) and a Clinical Frailty Score of 4 out of 9 (3-6) were included. Only 6% reported HFNC tolerability issues. The overall survival rate was 25% at hospital discharge. CONCLUSIONS: This study suggests that, when preferred, HFNC in the wards could be a potential rescue therapy for respiratory failure in vulnerable COVID-19 patients.

Covid-19 Pneumonia and Ventilation-induced Lung Injury: A Case Report.

We present the case of a 67-year-old male patient, who was admitted to the intensive care unit for hypoxemic respiratory failure due to severe COVID-19 pneumonitis, requiring mechanical ventilation. Despite close monitoring using transpulmonary pressure measurements and interventions to pursue lung-protective ventilation, the patient developed extensive barotrauma including a right-sided pneumothorax, subcutaneous emphysema and pneumomediastinum while on pressure support ventilation. We hypothesize that the high respiratory drive that COVID-19 patients seem to exhibit, combined with diffuse alveolar injury and increased alveolar pressure, resulted in gross barotrauma. CONCLUSION: The respiratory characteristics that COVID-19 patients seem to exhibit might expose those on mechanical ventilation to an increased risk of developing ventilation-induced lung injury. This case emphasizes that caution should be taken in the respiratory treatment of patients with COVID-19 pneumonitis.