Background: Heated, humidified, high-flow nasal cannula (HHFNC) oxygen therapy allows optimal humidification of inspired gas at high flows and creates a distending pressure similar to nasal continuous positive airway pressure [1]. It has been safely used in adults with moderate hypoxemia with few complications [2, 3]. Hereby, we report serious complications occurred during HHFNC oxygen therapy. Case presentation: A 53-year-old female with hemophagocytic lymphohistiocytosis (HLH) was admitted to the intensive care unit because of respiratory failure. After weaning from mechanical ventilation which lasted for 2 weeks, HHFNC therapy at 40 L/min with an FiO2 of 0.5 was started for hypoxemia. Four days later, dyspnea and hypoxemia occurred and chest X-ray and CT scan revealed localized pneumothorax, subcutaneous emphysema, and massive pneumomediastinum. After cessation of HHFNC, respiratory condition improved. Conclusion: Subcutaneous emphysema, pneumothorax, and pneumomediastinum should be notified as a serious complication during HHFNC therapy.

BackgroundWe describe a pediatric patient who suffered from critical abdominal distention caused by a combination of humidified, high-flow nasal cannula (HHFNC) oxygen therapy and nasal airway.Case presentationA 21-month-old boy with a history of chronic lung disease was admitted to the intensive care unit (ICU). Immediately after admission, his airway was established using a tracheal tube and mechanical ventilation was started. Five days after the commencement of mechanical ventilation, finally, his trachea was extubated. Immediately after extubation, HHFNC therapy at 20 L/min with an FiO2 of 0.35 was applied. However, severe stridor was observed, then a nasal airway was placed in the left nostril. However, he became restless. Critical abdominal distention was observed. A subsequent chest X-ray revealed that the nasal airway was placed too deeply, and the gastrointestinal air was severely accumulated. Immediately, the nasal airway was removed, and HHFNC flow was reduced to 10 L/min. Frequent suctioning and continuous gastric drainage were required, which achieved gradual improvement of respiratory condition.ConclusionsWe need to recognize that HHFNC therapy is one of the positive pressure ventilation system. Therefore, HHFNC therapy might cause the similar adverse events to noninvasive pressure ventilation.

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Since February 2021, health care workers in Japan have been preferentially vaccinated with a messenger RNA vaccine (BNT162b2/Pfizer) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While many studies have confirmed that this vaccine is highly effective in reducing hospitalizations and deaths from coronavirus disease 2019 (COVID-19), antibody titers tend to decline at 3 months, leading to a risk of breakthrough infections. Thus, information is needed to support decision making regarding the third vaccination. In this study, we investigated transition of the anti-SARS-CoV-2 receptor-binding domain (RBD) IgG and neutralizing antibody titers of 41 vaccinated Japanese healthcare workers. Samples were collected seven times starting 1 week before vaccination until 6 months post-vaccination. Anti-SARS-CoV-2 RBD IgG levels peaked at 7 days after the booster, then declined over time and decreased to <10% at 6 months after the booster. Workers with low anti-SARS-CoV-2 RBD IgG levels also had low neutralizing antibody titers. These data support the active use of boosters for healthcare workers, especially for those with low anti-SARS-CoV-2 RBD IgG levels.

Since February 2021, healthcare workers in Japan have been preferentially vaccinated with a messenger RNA vaccine (BNT162b2/Pfizer) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While many studies have confirmed that this vaccine is highly effective in reducing hospitalizations and deaths from coronavirus disease 2019 (COVID-19), antibody titers tend to decline at 3 months, leading to a risk of breakthrough infections. Thus, information is needed to support decision making regarding the third vaccination. In this study, we investigated transition of the anti-SARS-CoV-2 spike protein receptor-binding domain (RBD) IgG and neutralizing antibody titers of 37 vaccinated Japanese healthcare workers. Samples were collected six times starting