RESUMO
BACKGROUND: Mediastinal emphysema is a condition in which air enters the mediastinum between the connective tissue spaces within the pleura for a variety of reasons. It can be spontaneous or secondary to chest trauma, esophageal perforation, medically induced factors, etc. Its common symptoms are chest pain, tightness in the chest, and respiratory distress. Most mediastinal emphysema patients have mild symptoms, but severe mediastinal emphysema can cause respiratory and circulatory failure, resulting in serious consequences. CASE SUMMARY: A 75-year-old man, living alone, presented with sudden onset of severe epigastric pain with chest tightness after drinking alcohol. Due to the remoteness of his residence and lack of neighbors, the patient was found by his nephew and brought to the hospital the next morning after the disease onset. Computed tomography (CT) showed free gas in the abdominal cavity, mediastinal emphysema, and subcutaneous pneumothorax. Upper gastrointestinal angiography showed that the esophageal mucosa was intact and the gastric antrum was perforated. Therefore, we chose to perform open gastric perforation repair on the patient under thoracic epidural anesthesia combined with intravenous anesthesia. An operative incision of the muscle layer of the patient's abdominal wall was made, and a large amount of subperitoneal gas was revealed. And a continued incision of the peritoneum revealed the presence of a perforation of approximately 0.5 cm in the gastric antrum, which we repaired after pathological examination. Postoperatively, the patient received high-flow oxygen and cough exercises. Chest CT was performed on the first and sixth postoperative days, and the mediastinal and subcutaneous gas was gradually reduced. CONCLUSION: After gastric perforation, a large amount of free gas in the abdominal cavity can reach the mediastinum through the loose connective tissue at the esophageal hiatus of the diaphragm, and upper gastrointestinal angiography can clarify the site of perforation. In patients with mediastinal emphysema, open surgery avoids the elevation of the diaphragm caused by pneumoperitoneum compared to laparoscopic surgery and avoids increasing the mediastinal pressure. In addition, thoracic epidural anesthesia combined with intravenous anesthesia also avoids pressure on the mediastinum from mechanical ventilation.
RESUMO
Numerous scientific satellites require micronewton thrusters for compensating environmental disturbances. The mass flow control proportional valve plays a crucial role in precisely regulating the thrust. To meet the high resolution and wide range requirements of the thrusters, this paper introduces a novel proportional valve with two sets of independently controllable piezoelectric stack. One set of the piezo-stack is used to compensate the stroke loss of the valve core, mainly caused by the deformation of the valve seat. The valve sealing mechanism is carefully analyzed to reduce the stroke loss. Another set of the stack works as the primary actuator, enabling the high mass flow control resolution. Two sets of independently controlled piezoelectric stacks not only expand the range and improve the range ratio but also provide redundancy and enhance reliability. This means that the actuator can still operate at lower ranges even if one piezo-stack is damaged. The piezo-actuators are assembled using U-shaped connectors, creating a compact and space-efficient overall design. Experimental tests have been conducted to verify the performance of the valve, which demonstrated a mass flow range of 0-675 µg/s with a resolution better than 0.1 µg/s and a flow noise below 0.1 µg/s/Hz1/2 at 0.1 mHz-1 Hz.