Air leaks, pneumatoceles, and air spaces in Covid-19 pneumonia

The recent report of SARS-CoV-2-related bilateral pneumothorax [1], and similar reports of covid-19-related bilateral pneumothorax [[2], [3], [4]] appear to be a predictable consequence of the observation that SARS-CoV-2 pulmonary lesions have a predominantly peripheral and subpleural distribution [5,6], and may be associated with the presence of “emphysema “[5], “cystic air spaces” [6], or “cystic changes” [7], all three terms arguably synonymous with pneumatocele. Rupture of a pneumatocele, in turn, may be the trigger for occurrence of pneumothrax, pneumomediastinum, and pneumopericardium, respectively. SARS-CoV-2-related pneumatoceles may be multiple [8], arguably simulating emphysema, or only a few may be present, when they tend to be labelled as pneumatoceles, instead. The size of covid-19-related pneumatoceles is also highly variable, with some falling into the category of giant bullae [9]. Either in the context of multiple pneumatoceles or in the context of the isolated giant bulla, pneumothorax is an entirely predictable complication [8,9], which may be compounded by the occurrence of pneumomediastinum, not only when pneumothorax is bilateral [3,4], but also when it is unilateral [9].

Inspection of computerised tomography images of SARS-CoV-2 pneumonia should include a diligent search for even the minutest subpleural pneumatoceles so as to raise awareness of the risk of pneumothorax, pneumomediastinum and pneumopericardium. In a retrospective study of 78 consecutive patients with proven SARS-CoV-2-related pneumonia, Werberich et al. documented cystic air space changes in 37.5% of their subjects. Those workers commented that “few reports have described these features”, and they cited a speculation that these cystic air spaces might represent the development of small pneumatoceles [6]. In Shi et al. 10% of 81 symptomatic patients with Covid-19-related pneumonia had “cystic changes” identified on computed tomography [7]. In Qi et al. “emphysema” was documented by computed tomography in 5.3% of their 57 subjects with covid-19 pneumonia [5].

Even in an asymptomatic SARS-CoV-2 patient with minimal pulmonary involvement air leaks can still occur, as shown in an otherwise well 23 year old patient who had spontaneous pneumomediastinum in association with “inconspicuous ground glass opacity in the lower left inferior lobe consistent with initial phase of COVID-19 pneumonia”[10]. Although no pneumatocele was identified at the time of presentation, it may well be that antecedent rupture of an unrecognised pneumatocele could have triggered the occurrence of pneumomediastinum.