IntroductionSeveral reports have described the usefulness of a high-flow nasal cannula (HFNC). However, the physiological mechanisms of this system are unclear. In the current study, various methods were used to investigate the physiological mechanisms of an HFNC in healthy volunteers.MethodsThe physiological mechanisms of the constant-flow and constant-pressure models of HFNC were studied in 10 healthy volunteers by the oesophageal balloon method, the electrical impedance method and the forced oscillation technique (FOT).ResultsThe tidal volume (TV) increased markedly during HFNC (off, 30 L/min, 50 L/min: 685.6±236.5 mL, 929.8±434.7 mL, 968.8±451.1 mL). The end-inspiratory oesophageal pressure (EIOP) was not significantly different, but there was a tendency for it to decrease. HFNC 30 L/min and 50 L/min, the increment in TV and the difference in EIOP showed strong negative correlations (p=0.0025, 0.003). The end-expiratory oesophageal pressure (EEOP) increased. The respiratory system reactance at 5 Hz (X5) by FOT decreased significantly. There was a flow rate-dependent EEOP increase, and the positive end-expiratory pressure (PEEP) effect of HFNC was confirmed. There was a correlation between the difference in X5 and the difference in EEOP during HFNC 30 L/min and 50 L/min, with correlation coefficients of 0.534 and 0.404 (p=0.112, 0.281). The amount of change in EEOP and the fluctuation in X5 were positively correlated.ConclusionsThe PEEP effect of HFNC was confirmed by the electrical impedance method and FOT. The increment in TV and the difference in EIOP of HFNC showed strong negative correlations.

Background Immunoglobulin G4 (IgG4)-related disease is a chronic inflammatory disease that was recognized in 2011. Pleuritis associated with IgG4-related disease is rare and can be difficult to diagnose. Although there have been previous reports on pleuritis associated with IgG4-related disease by thoracoscopic findings, this is the first to observe pleuritis with IgG4-related disease from normal pleural thoracoscopic findings. Case presentation A 70-year-old Japanese female treated for breast cancer 33 years ago was referred to our hospital complaining of dyspnea on exertion. Chest computed tomography (CT) revealed left pleural effusion that was exudative and predominant with lymphocytes, elevated adenosine deaminase (ADA) and Class III cytology (malignancy suspected). Subsequently, thoracoscopic pleural biopsy was performed for definitive diagnosis. Although pleural macroscopic findings appeared normal, we performed pleural biopsy at random sites. This patient was negative for mycobacterium tuberculosis, and neither granulomas nor malignant cells were found in the collected specimens. An infiltration of inflammatory cells, mainly plasma cells and lymphocytes, was observed. Immunostaining revealed the number of IgG4-positive plasma cells was 102/high power field (HPF), and the percentage of IgG4 positive/immunoglobulin G (IgG)-positive cells was 41.4%. Since IgG4 serum levels were high and IgG4-related submandibular sialadenitis was also observed, a definitive diagnose of pleuritis associated with IgG4-related disease was confirmed. Conclusions We diagnosed pleuritis associated with IgG4-related disease by thoracoscopic pleural biopsy samples taken from a visually normal pleura. Although exudative pleural effusion with high ADA and lymphocyte predominance is a characteristic of tuberculous pleuritis, other diseases might be present. Since thoracoscopy can increase the diagnostic yield, pleural biopsy should be considered even if thoracoscopic pleural findings are deemed normal.

BackgroundPrimary localized amyloidosis presenting as an isolated mediastinal mass is extremely rare, especially in the thymus. Sclerosing thymoma is also an extremely rare anterior mediastinal tumor, pathologically characterized by extensive sclerotic lesions with hyalinization and calcification. Only 14 cases of sclerosing thymoma and five cases of thymic amyloidosis have been reported to date.Case presentationA 78-year-old Japanese woman was diagnosed as having sclerosing thymoma (Masaoka stage IVa pericardial dissemination)-like thymic amyloidoma. She was diagnosed as having either lung cancer or mediastinal tumor with pericardial dissemination, and received palliative treatment. Three years later, she was readmitted with a complaint of general malaise. Since minimal change nephrotic syndrome was suspected based on the disease onset and selectivity index of urinary protein, steroid pulse therapy was started. Subsequently, because a marked reduction in tumor size was observed during maintenance treatment with prednisolone, a thoracoscopic needle biopsy was performed for a definitive diagnosis. According to the pathological findings and clinical investigations, a final diagnosis of sclerosing thymoma (Masaoka stage IVa pericardial dissemination)-like thymic amyloidoma was made.ConclusionsThis is a case report of sclerosing thymoma-like thymic amyloidoma. Both sclerosing thymoma and thymic amyloidoma are extremely rare diseases: only 14 cases of sclerosing thymoma and five cases of thymic amyloidosis have been reported to date. In either diagnosis, our case is the first case in which marked reduction in tumor size was observed with steroid therapy. All reported cases of sclerosing thymomas underwent surgical resection, but steroid therapy to sclerosing thymoma has not been reported. It is still unknown whether steroid therapy is effective or not. The hyalinized components of sclerosing thymoma possibly contain amyloid deposits. The marked reduction in tumor size with steroid therapy may result in amyloid deposits. The association between sclerosing thymoma and thymic amyloidoma remains uncertain. Sclerosing thymoma should be stained with Congo red.

Background Pneumothorax is defined as the presence of air or gas in the pleural cavity. Secondary pneumothorax usually occurs in patients with overt underlying lung disease, most commonly chronic obstructive pulmonary disease (COPD). Patients with poor lung function often suffer from pneumothorax with a persistent air leak. Various strategies have been employed in the treatment of such refractory pneumothorax. Bronchial occlusion with an Endobronchial Watanabe Spigot (EWS) (Novatech, Grasse, France) has been shown to be useful in treating prolonged bronchopleural fistulas. Although the effects of bronchial occlusion with EWS are known, refractory pneumothorax often involves multiple affected bronchi, and in some cases the affected bronchi cannot be easily identified. In addition, secondary pneumothorax associated with advanced lung cancer often prolongs the treatment of pneumothorax, which can significantly reduce patients’ quality of life and prognosis. Case presentation We report a case of refractory pneumothorax where collateral ventilation was successfully treated by bronchial occlusion of the affected bronchi using multiple methods. In August 2019, an 80-year-old Japanese man with asthma and COPD overlap was admitted for exacerbation triggered by respiratory tract infection. During hospitalization, he presented with chest pain due to pneumothorax. Subsequently, a chest drain tube was inserted and pleurodesis was performed; however, the lung could not be sufficiently expanded and an air leak remained. Further investigation revealed a tumor suspicious for lung cancer at the entrance of the left upper lobe bronchus. Due to poor lung function, surgical treatments were deemed high risk. Therefore, we performed bronchial occlusion using the Endobronchial Watanabe Spigot (EWS). Because we could not determine the affected bronchi by computed tomography (CT), we located the affected bronchi by balloon occlusion test and bronchography with iopamidol. After occlusion, the air leak decreased but still persisted. Thus, we performed pleurodesis twice, and the air leak ceased completely. Conclusions Refractory secondary pneumothorax, which affected multiple bronchi and developed into collateral ventilation due to lung cancer, was treated successfully with bronchial occlusion and EWS. In cases where the affected bronchi cannot be determined by the balloon occlusion test, bronchography with iopamidol might be an effective treatment.

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