Discussion:
Regarding the disease course and imaging characteristics of the current case, a number of clinical implications are discussed below. The lung CT imaging suggested that the lesions in both lungs progressed in the first month of the disease course, with the last CT images showing significant improvements in both lung lesions (Figure 1). For most patients with COVID-19, especially younger or middle-aged patients, the clinical course may be self-limiting if they are provided with adequate symptomatic relief and supportive treatment. In patients recovering from COVID-19 (without severe respiratory distress during the disease course), lung abnormalities on chest CT were the most severe approximately 10 days after the initial onset of symptoms. The lesions were then gradually absorbed after two weeks [5]. In this case, the lung lesions started to gradually diminish one month after the onset of symptoms. This suggests that mechanical ventilation treatment and ECMO should be sustained for a more extended time period in some patients with severe or critical COVID-19.
During the course of the disease, repeat and refractory pneumothorax presented. The main reasons and mechanisms for pneumothorax are summarized below. First, the patient had an intestinal feeding tube placed by gastroscopy, after which hypertension and sinus tachycardia presented. Then, chest radiography showed right lung pneumothorax. The attending doctors considered that because of severe nausea and breath-holding, the pressure in his airways had increased, causing the rupture of the tracheal membrane and mediastinal emphysema, which in turn caused pneumothorax. Second, for this patient, invasive mechanical positive pressure ventilation had both positive and negative effects. Excessive positive pressure ventilation led to the excessive expansion of the alveoli, causing severe damage to the barrier between the lung epithelium and the endothelium. This enabled gas to enter the lung parenchyma and leak from the interstitial space, causing pneumothorax and subcutaneous emphysema. Finally, COVID-19 caused direct damage to the alveolar cells, and subsequently, the accumulation of inflammatory cells and the release of inflammatory mediators (IL-1, IL-6, and TNF-α) promoted the occurrence and development of lung injury.
Therefore, lung-protective ventilation strategies are required for patients with COVID-19, and could be implemented in the following order: limit tidal volume, limit peak airway pressure, and use suitable muscle relaxants. The patient was put on ECMO due to severe lung injury and reduced peak airway pressure. However, without pneumothorax in the right lung, the patient would not have required ECMO treatment. Therefore, in the clinical diagnosis and treatment of COVID-19, attention to iatrogenic injuries should be given.