Figure 1. Representative chest computed tomographic images of elderly patients with COVID-19 who received early or late high-flow nasal cannula (HFNC). (A–D) A 72 year old man with COVID-19 received early HFNC therapy when his PaO2/FiO2 was 256 mmHg. (A) Image obtained on day 1 showed small ground-glass opacity lesion (red arrow) in the middle lobe of the right lung; (B) image obtained on day 5 showed enlarged lesion in right lung and several small areas of new exudative lesions in outer basal segment of lower lobe of left lung; (C) image obtained on day 18 showed the lesion in the middle lobe of the right lung reduced more than 50%, and clear interstitial lesions were found in the lower lobes of both lungs; (D) image obtained day 24 showed the lesions were further reduced and became lighter in density (red arrow). HFNC was discontinued on day 23, and this patient was discharged on Day 26. (E, F) A 68 year old man with COVID-19 received late HFNC oxygen therapy when his PaO2/FiO2 was 186 mmHg. (E) Image obtained on day 1 showed a few patchy exudative lesions and cord like fibrosis in bilateral lobes of both lungs (red arrow); (F) image obtained on day 7 showed original lesions were obviously increased, and parenchymal lesions (such as consolidation and air bronchogram) in the middle and lower lobes of right lung, as well as appearance of interstitial lesions in lower left lung; (G) image obtained on day 21 showed increased patchy exudative lesions and interstitial lesions with light density (a few reticular lung changes) in lower left lung; (H) image obtained on day 33 showed a few grid lung changes and subpleural lines in the right lower lobe. This patient required invasive mechanical ventilation on day 23, and died of cardiac arrest on day 36 after admission.