Frequency, risk factors, clinical characteristics and outcomes of spontaneous pneumothorax in patients with Covid-19: A case-control, emergency medicine-based multicenter study

Abstract Background Recent reports of COVID-19 patients developing pneumothorax mainly correspond to case reports in mechanically-ventilated patients. The real incidence, clinical characteristics and outcome of spontaneous pneumothorax (SP) as a form of COVID presentation remains to be defined. Research question Do the incidence, risk factors, clinical characteristics and outcomes of SP in COVID-19 patients attending emergency departments (ED) differ compared to COVID patients without SP and non-COVID patients with SP? Study design and methods: This case-control study retrospectively reviewed all COVID patients diagnosed with SP(case group) in 61 Spanish EDs(20% of Spanish EDs) and compared them with two control groups: COVID patients without SP and non-COVID patients with SP. Relative frequencies of SP were estimated in COVID and non-COVID patients in the ED and annual standardized incidences were estimated for both populations. Comparisons between cases and controls included 52 clinical, analytical and radiological characteristics and 4 outcomes. Results We identified 40 SP in 71,904 patients with COVID-19 attending EDs(0.56‰, 95%CI=0.40-0.76‰). This relative frequency was higher than that of non-COVID patients(387/1,358,134, 0.28‰, 95%CI=0.26-0.32; OR=1.93, 95%CI=1.41-2.71). The standardized incidence of SP was also higher in COVID patients (34.2 versus 8.2/100,000/year; OR=4.19, 95%CI=3.64-4.81). Compared with COVID patients without SP, COVID patients developing SP more frequently had dyspnea and chest pain, low pulsioxymetry, tachypnea and increased leukocyte count. Compared to non-COVID patients with SP, cases differed in 19 clinical variables, the most prominent being a higher frequency of dysgeusia/anosmia, headache, diarrhea, fever and lymphopenia (all with OR>10). All the outcomes measured, including in-hospital death, were worse in cases than in both control groups. Interpretation SP as a form of COVID presentation at the ED is unusual (