A radiological predictor for pneumomediastinum/pneumothorax in COVID-19 ARDS patients

Abstract

Purpose: To determine whether Macklin effect (a linear collection of air contiguous to the bronchovascular sheath) on baseline CT imaging is an accurate predictor for subsequent pneumomediastinum (PMD)/pneumothorax (PNX) development in invasively ventilated patients with COVID-19-related acute respiratory distress syndrome (ARDS).

Materials and methods: This is an observational, case-control study. From a prospectively acquired database, all consecutive invasively ventilated COVID-19 ARDS patients who underwent at least one baseline chest CT scan during the study time period (February 25th, 2020-December 31st, 2020) were identified; those who had tracheal lesion or already had PMD/PNX at the time of the first available chest imaging were excluded.

Results: 37/173 (21.4%) patients enrolled had PMD/PNX; specifically, 20 (11.5%) had PMD, 10 (5.8%) PNX, 7 (4%) both. 33/37 patients with subsequent PMD/PNX had Macklin effect on baseline CT (89.2%, true positives) 8.5 days [range, 1-18] before the first actual radiological evidence of PMD/PNX. Conversely, 6/136 patients without PMD/PNX (4.4%, false positives) demonstrated Macklin effect (p < 0.001). Macklin effect yielded a sensitivity of 89.2% (95% confidence interval [CI]: 74.6-96.9), a specificity of 95.6% (95% CI: 90.6-98.4), a positive predictive value (PV) of 84.5% (95% CI: 71.3-92.3), a negative PV of 97.1% (95% CI: 74.6-96.9) and an accuracy of 94.2% (95% CI: 89.6-97.2) in predicting PMD/PNX (AUC:0.924).

Conclusions: Macklin effect accurately predicts, 8.5 days in advance, PMD/PNX development in COVID-19 ARDS patients.

Keywords: Acute respiratory distress syndrome; COVID-19; Mechanical ventilation; Pneumomediastinum; Pneumothorax; Tomography, X-ray computed.

Fig. 1

Inclusion and exclusion criteria flowchart. COVID-19: coronavirus disease 2019; ARDS: Acute Respiratory Distress Syndrome; IMV: invasive mechanical ventilation; CT: Computed Tomography; PMD: pneumomediastinum; PNX: pneumothorax.

Fig. 2

Macklin effect in a mechanically ventilated COVID-19 patient. Lung parenchyma windowed CT images demonstrate [a] a crescent collection of air contiguous to the right upper lobar bronchovascular sheath (that is, Macklin effect – white arrow). Two days later [b], pneumomediastinum occurred.

Fig. 3

Macklin effect accuracy. ROC curve analysis showing overall accuracy of the Macklin effect in predicting pneumothorax and/or pneumomediastinum [a] (AUC: 0.924), pneumothorax alone [b] (AUC: 0.978) and pneumomediastinum alone [c] (AUC: 0.904).

Fig. 4

Topographical distribution of Macklin effect and temporal interval before pneumothorax/pneumomediastinum occurrence. [a] According to the bronchial order (lobar [green dots, upper line], segmental [blue dots, mid line] or subsegmental [red dots, lower line]) most adjacent to the Macklin effect observed, the smaller the bronchovascular sheath involved, the longer the temporal advance before pneumothorax/pneumomediastinum (p < 0.001, R = − 0.896). Each dot represents a patient with Macklin effect on baseline CT scan; larger dots means that multiple patients with Macklin effect share the same temporal advance before pneumothorax/pneumomediastinum development. [b] Kaplan Meier curve demonstrating statistically significant difference between patients with “centrally-distributed” Macklin effect and those with “peripherally-distributed” Macklin effect in terms of temporal interval before pneumothorax/pneumomediastinum occurrence. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)