Non invasive mechanical ventilation as a rare cause of pulmonary barotrauma in course of COVID 19.

A 59-year-old patient with no co-morbidities was admitted to hospital with a two weeks history of fever, cough and dyspnoea. A chest x ray documented bilateral subpleural infiltrates consistent with pneumonia. Arterial blood gas test was compatible with mild ARDS. A RT-PCR from a nasopharyngeal swab confirmed a SARS-CoV-2 infection.

During hospitalization three chest CTs were performed. The first CT at day 10 showed  pneumomediastinum with air decompressing along cervical fascial planes into subcutaneous tissue (Fig 1a). Air (Fig 1b, arrow) consistent with pulmonary interstitial emphysema (PIE) was seen along with peribronchovascular bundles. No pneumothorax was present. Diffuse ground-glass opacities (GGO) were present bilaterally in all lobes (Fig 1c) with areas of “crazy paving” increased density and consolidations with a prevalent subpleural distribution. A score of lung parenchymal involvement was estimated visually from 50 to 75%.

The second CT at day 19 showed the same range of parenchymal involvement, characterized by irregular bands of dense consolidation (Fig 2). Pneumomediastinum had dramatically reduced; no more soft tissue emphysema and PIE were seen.

A contrast CT scan at day 30 ruled out pulmonary embolism. Parenchymal changes were still present with GGO and areas of irregular, mild consolidation (Fig 3). No more signs of barotrauma were present.

The clinical spectrum of SARS-CoV-2 pneumonia ranges from mild to critically ill cases and morbidity and mortality is largely due to acute respiratory distress syndrome (ARDS); as described in early reports from Wuhan about 30 % of patients with COVID-19 required mechanical ventilation [1].

Mechanical positive pressure ventilation is the most common treatment for acute respiratory failure (ARF); it can be delivered through a noninvasive (nasal or face mask, nasal plugs), or an invasive interface (endotracheal tube, tracheostomy).

Pulmonary barotrauma is defined as the presence of extra alveolar air due to lung injury. Barotrauma can be a complication of mechanical ventilation, either invasive (IV) or non-invasive (NIV), and may be associated with increased morbidity and mortality [2]. Mechanical ventilation may determine alveolar rupture, which results in air leakage into extra-alveolar interstitium. Interstitial air may dissect along perivascular sheaths towards pleural space, mediastinum and skin leading to pulmonary interstitial emphysema (PIE), pneumothorax, pneumomediastinum and subcutaneous emphysema [3]. The incidence of barotrauma depends on the underlying lung pathology; recent papers report an incidence of 10% averaged between different populations [4]. Keeping pressures and volumes low is considered a lung-protective ventilation procedure. Pressures related to NIV are lower compared with IV, thus barotrauma is reported to be rare in the former group. NIV is the initial approach in patients with signs of mild ARF [5-7].

Lung barotrauma is a clinical diagnosis; imaging is crucial as regards diagnosis, follow-up and treatment planning.

Chest x-ray is the first line exam to identify signs of barotrauma, specifically pneumothorax; CT can precisely characterize all manifestations of lung injury and is usually performed as a second line exam [6].

We report the benign course of a 59 years patient with a SARS-CoV-2 pneumonia-causing mild ARDS, who underwent NIV mechanical ventilation. A first CT scan was requested after ten days because of clinical worsening ; lung infiltrates involved more than 50% of lung parenchyma and some manifestations of lung barotrauma were noted. Pneumonia was treated with antiviral agents, while the non-life-threatening manifestations of barotrauma were monitored radiographically. After nine days another CT scan was performed in order to monitor antiviral therapy; a last CT scan was done at day 30 from admission because of chest pain. The clinical situation gradually improved with normalization of the arterial blood gas values; reduction of lung parenchymal consolidations and self-limitation of the manifestations of barotrauma were progressively demonstrated. The patient was discharged and sent to rehabilitation after 38 days of hospitalization.