Figure 3 CT of chest on Day 9: No abnormal density shadow was observed in both lungs. No obvious abnormality was observed in mediastinum and bilateral armpit.
DISCUSSION
Hyperbaric oxygen as a routine treatment for acute carbon monoxide poisoning can not only convert the carboxyhemoglobin in mitochondrial cytochrome to oxygenated hemoglobin during carbon monoxide poisoning, but also reduce the permanent neurological and emotional effects of carbon monoxide poisoning[4]. In addition, hyperbaric oxygen therapy is particularly important in preventing long-term sequelae,it can reduce acute mortality and mortality after one year[5, 6] .In addition to acute carbon monoxide poisoning, we also found successful cases of pneumomediastinum treated with hyperbaric oxygen[7-14].
In this case, the main symptoms were acute carbon monoxide poisoning, drowsiness, bilateral pneumonia, and pneumomediastinum. After 11 hours of acute carbon monoxide poisoning, the patient was placed in 1.3 ATA chamber with compressed air. HBOT protocol was 70 minutes at 1.3 ATA with both 20 minutes of compression and decompression. After only one treatment, it was found that his consciousness was recovered after the poisoning. Computed tomography shows that pneumomediastinum and bilateral pneumonia were also reduced. The next day, the treatment was extended to 100 minutes at 1.3 ATA with both 20 minutes of compression and decompression. And the same HBOT for the next week.
In another case report we found that hyperbaric oxygen therapy in a patient with pneumomediastinum due to diving[8]. Four hours after he was injured, the patient was placed on the chamber that pressurised to 1.3 ATA, Symptoms improved after 60 minutes of 100% oxygen inhalation via a built in breathing system (BIBS) mask. Also, in another report, a 13-year-old boy with a helium-filled brain embolism and pneumomediastinum received 40 minutes of air at 165 fsw, 100 percent oxygen for 3 hours at 60 fsw, and then 100 percent oxygen at 30 fsw. The patient’s reported symptoms completely disappeared[7].Combined with the above case and the case in this paper, we assume that the patient may not require such a extensive recompression to achieve the goal of symptom relief. Maybe 10 fsw is enough to make his symptoms go away.
In an example of a patient who died due to a diving accident, it was clear that the patient was in urgent need of HBO treatment due to bilateral tension pneumothorax and pneumomediastinum caused by DCS. However, due to the shortage of hyperbaric oxygen rooms in the local area and the shortage of personnel, the patient could not receive timely treatment even when he was in an important indication[15].
These examples undoubtedly show that in the face of patients with pneumomediastinum, timely HBO treatment is very important. After the primary treatment plan is clear, the parameter setting of hyperbaric oxygen therapy is also a question worth studying. Whether we can achieve the best treatment effect through the minimum parameter setting, so as to reduce the complications caused by hyperbaric oxygen therapy. The 1.3 ATA HBO therapy used in this case has not been found to have recurrence or complications in the follow-up of the patient within half a year after discharge.
The common pneumomediastinum is usually caused by mechanical ventilation[16] or DCS, but in this case, neither of these reasons exists. Given the presence of COVID-19 pneumonia, we considered that COVID-19 had caused his symptoms of pneumomediastinum. It has been speculated that the pathophysiological mechanism of its occurrence is diffuse alveolar damage and alveolar rupture, leading to interstitial emphysema and air tracking along the bronchoalveolar sheath to the mediastinum[17]. It is mentioned in this article that high serum lactate dehydrogenase may be positively correlated with the development of pneumomediastinum in COVID-19 patients[17].
A study from China reported two patients with COVID-19 pneumonia, patients were treated with 1.5 ATA HBO with an oxygen concentration of more than 95% for 60 minutes per treatment, once a day for one week. For both patients, dyspnea and shortness of breath were immediately alleviated after the first HBO2 treatment[18]. Gorenstein et al reported a study of 20 COVID-19 patients treated with 2 ATA of hyperbaric oxygen therapy for 90 minutes daily and propensity matched controls. The results show that the in-hospital mortality rate and time to mechanical ventilation are higher in propensity matched control group comparing to cases treated with HBOT [19]. In America, 5 COVID-19 patients received hyperbaric oxygen therapy for 90 minutes at 2.0 ATA between 13 and 20 April 2020.The final results demonstrated that all the patients recovered without the need for mechanical ventilation[20]. Although the parameters in these reports are different from the 1.3ATA we used, the final results are all positive. When acute carbon monoxide poisoning was combined with pneumomediastinum due to COVID-19, we found that inhalation of hyperbaric oxygen had the desired therapeutic effect. This provides a new clinical evidence to treating not only acute carbon monoxide poisoning but also the complications of COVID-19 with HBO.
In addition, computed tomography (CT) can be an important complement to timely diagnosis and identification of the causes of respiratory impairment and lung complications associated with COVID-19[21].
CONCLUSION
In conclusion, this case demonstrates a clear benefit of hyperbaric oxygen therapy in the treatment of pneumomediastinum caused by COVID-19 pneumonia and carbon monoxide poisoning.
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