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.