COVID-19 ARDS: a review of imaging features and overview of mechanical ventilation and its complications

Abstract

The first cluster of cases of COVID-19 pneumonia was reported on December 31, 2019. Since then, this disease has spread rapidly across the world, and as of September 17, 2021, there are 226,844,344 cases of COVID-19 worldwide with 4,666,334 deaths related to COVID-19. While most COVID-19 cases are mild, some cases are severe with patients developing acute respiratory distress syndrome (ARDS). The pathophysiology of ARDS includes damage to the alveolar epithelium that leads to increased permeability of the alveolar epithelial barrier causing hyaline membrane formation, interstitial edema, and alveolar edema that results in severe hypoxia. Patients with COVID-19 ARDS are supported by non-invasive or invasive mechanical ventilation with an aim to improve oxygenation and maintain adequate blood oxygen levels. Increased intra-alveolar pressure while on mechanical ventilation may lead to alveolar rupture and thus barotrauma-related injuries such as lung tension cysts, pulmonary interstitial emphysema (PIE), pneumomediastinum, pneumopericardium, and pneumothorax. Recent studies have shown that the rate of barotrauma-related events is higher in patients with COVID-19 ARDS compared to patients with ARDS secondary to other etiologies. Radiologists should be aware of the imaging features of COVID-19 ARDS as well as the complications of mechanical ventilation. This educational manuscript will review the features of COVID-19 ARDS, discuss imaging of patients on mechanical ventilation, and review the imaging features of complications related to mechanical ventilation, including ventilator-associated lung injuries.

Keywords: ARDS; Acute respiratory distress syndrome; Complications of mechanical ventilation; Covid-19 ARDS; Endotracheal intubation; Pneumomediastinum; Pneumothorax.

Fig. 1

Chest CT findings showing typical imaging features of COVID-19 pneumonia. A—Axial non-contrast chest CT image in a 48-year-old man with COVID-19 pneumonia demonstrates peripheral ground glass opacities in the bilateral lungs (arrows). B—Axial contrast-enhanced chest CT image in a 68-year-old man with COVID-19 pneumonia shows bilateral peripheral nodular ground glass opacities (arrows). C—Axial contrast-enhanced chest CT image in a 72-year-old woman with COVID-19 pneumonia reveals ground glass opacities in the bilateral lungs with inter- and intralobular septal thickening with a crazy paving appearance

Fig. 2

Chest CT findings showing indeterminate imaging features of COVID-19 pneumonia. A—Axial contrast-enhanced chest CT image in a 38-year-old man with COVID-19 pneumonia shows bilateral peribronchovascular ground glass opacities (white arrows). B—Axial contrast-enhanced chest CT image in a 60-year-old man with COVID-19 pneumonia reveals diffuse bilateral ground glass opacities

Fig. 3

Chest CT findings showing atypical imaging features of COVID-19 pneumonia. A—Axial contrast-enhanced chest image in a 72-year-old man with RT-PCR test positive for COVID-19 demonstrates clusters of tree-in-bud nodules in the right middle lobe (arrows). B—Contrast-enhanced Axial chest CT image in a 58-year-old man with RT-PCR test positive for COVID-19 reveals a mass-like consolidation in the right lower lobe with a central area of lucency, consistent with a cavitation (arrow). C—Axial contrast-enhanced chest CT image in a 53-year-old man with RT-PCR test positive for COVID-19 shows small bilateral pleural effusions with mild interlobular septal thickening resembling pulmonary edema. D—Axial contrast-enhanced chest CT image in a 66-year-old man with positive RT-PCR for COVID-19 demonstrates consolidation in the left lower lobe (arrow)

Fig. 4

Serial frontal (AP) chest x-rays in a 64-year-old man showing rapid progression of COVID-19 ARDS A—Initial chest x-ray with faint airspace opacities in the right lower lung (arrow). B—Chest x-ray 2 days later shows increase in the airspace opacities in the right lower lung (white arrow) and retrocardiac opacity. C—Chest x-ray 2 days later (4 days from the initial exam) shows rapid progression of bilateral airspace opacities with a lower lobe predominance and near complete opacification of both the lungs. Also note that the patient is intubated and the presence of a right-sided infusion port

Fig. 5

Axial non-contrast images (A, B, & C) of the chest CT in a 68-year-old man with COVID-19 pneumonia demonstrate bilateral lung opacities with anteroposterior density gradient. Dense consolidations are seen in the most dependent portion of the lungs (arrows) with relative sparing of the more anterior portion of the lungs. While nonspecific, these findings favor COVID-19 ARDS. An endotracheal tube nasogastric tube are also present

Fig. 6

Frontal chest radiographs in a 64-year-old man with COVID-19 ARDS. A—Supine image of the chest shows dense consolidation in the left lower lung (arrow). B—Image of the chest acquired in prone position in the same patient within two hours demonstrates apparent improvement of consolidations in the left lower lung (arrow) which is positional. A right internal jugular central venous catheter is present

Fig. 7

Axial non-contrast chest CT images in a 44-year-old man with COVID-19 ARDS showing progressive development of fibrosis in the upper lobes with relative sparing of lower lobes. A and B—Initial CT images, show COVID-19 ARDS with dependent consolidations in the bilateral lungs (arrows) and relative sparing of the upper lobes. C and D—CT images from nine months later, show new fibrotic changes with traction bronchiectasis in the bilateral upper lobes (arrows) with improvement of bilateral lower lobe consolidations. E and F—CT images eight months later and one year 4 months from initial CT, show peripheral and peribronchial ground glass opacities and consolidations in the upper lobes with traction bronchiectasis (arrows). Lower lobes are spared from fibrotic changes showing that consolidations during ARDS are protective against the subsequent development of lung fibrosis

Fig. 8

A—Lung tension cysts. A—Axial non-contrast chest CT image in a 78-year-old man with COVID-19 pneumonia on mechanical ventilation shows cavitary lesion/lung tension cyst in the subpleural right lower lobe (arrow). B—Pulmonary interstitial emphysema. Non-contrast axial chest CT image in a 45-year-old man with COVID-19 ARDS on mechanical ventilation shows pulmonary interstitial emphysema (PIE). Note the linear lucency surrounding bronchi/ pulmonary artery which is consistent with PIE (black arrows). Air is seen anteriorly consistent with pneumomediastinum (white arrow). Also seen are dependent consolidative opacities in the posterior lower lobes consistent with COVID-19 ARDS (arrowheads)

Fig. 9

AP chest radiographs showing pneumomediastinum. A—AP chest radiograph in a 72-year-old male patient with COVID-19 ARDS on mechanical ventilation shows lucency surrounding the heart consistent with pneumomediastinum (arrows). B—AP chest radiograph in a 68-year-old man with COVID-19 ARDS on mechanical ventilation shows lucency adjacent to the left heart border (white arrow) and air outlining the lateral aspect of the left subclavian artery (black arrow) consistent with pneumomediastinum. An endotracheal tube, nasogastric tube, and right internal jugular central venous catheter are present

Fig. 10

Axial non-contrast chest CT images in a 72-year-old man with COVID-19 ARDS following mechanical ventilation with pneumomediastinum. A—Air with stranding in the anterior mediastinum consistent with pneumomediastinum (white arrow). Also note small left pneumothorax (black arrow). B—Air with stranding in the anterior mediastinum consistent with pneumomediastinum. Bilateral ground glass and consolidative opacities are consistent with known COVID-19 ARDS

Fig. 11

A—AP Chest x-ray in a 65-year-old man with COVID-19 ARDS on mechanical ventilation shows lucency in the right pleural space consistent with pneumothorax (arrow). A chest tube is present as well. B—Axial contrast-enhanced chest CT image in the same patient shows right pneumothorax (arrow) with chest tube. C—Coronal non-contrast chest CT image in a 55-year-old man with COVID-19 ARDS on mechanical ventilation shows large right tension pneumothorax with collapse of the right lung (arrowhead), with deviation of the heart and mediastinum to the contralateral side (thick arrow) and flattening of the right hemidiaphragm (thin arrow). A tracheostomy tube is also present in A & C

Fig. 12

A and B—Initial axial non-contrast chest CT images in a 68-year-old man show ground glass opacities in the left upper lobe and bilateral lower lobes concerning for COVID-19 pneumonia. The patient subsequently developed COVID-19 ARDS and was supported with mechanical ventilation. Axial contrast-enhanced CT images (C and D) were obtained two months later when the patient had increasing secretions and worsening fever. There are new consolidations in the right upper lobe (arrow) and worsening ground glass opacities in the lower lobes. Cultures from the endotracheal tube secretions were positive for Klebsiella pneumoniae and Streptococcus pneumoniae, consistent with ventilator associated pneumonia (VAP)

Fig. 13

Axial non-contrast chest CT images in a 94-year old man with tracheal rupture secondary to traumatic intubation. A—There is rupture of the right posterior wall of the trachea (white arrow) with subcutaneous emphysema in the right anterior chest wall (black arrow). B—Extensive pneumomediastinum (white arrow) and right anterior chest wall emphysema (black arrow) are also seen. Bilateral consolidative opacities (arrowheads) are also present consistent with COVID-19 ARDS