|Ahead of print publication
Computed tomography severity index in nCovid19 pneumonia: Clinicians perspective
M Vishnu Sharma
Department of Respiratory Medicine, A. J. Institute of Medical Sciences and Research Centre, Mangalore, Karnataka, India
|Date of Submission||30-Jun-2021|
|Date of Decision||13-Feb-2022|
|Date of Acceptance||14-Feb-2022|
M Vishnu Sharma,
Department of Respiratory Medicine, A. J. Institute of Medical Sciences and Research Centre, Kuntikana, Mangalore, Karnataka
Source of Support: None, Conflict of Interest: None
Computed tomography (CT) scan of the thorax plays an important role in diagnosis and management of nCovid19 pneumonia. Chest CT scan is useful in diagnosing real-time polymerase chain reaction negative nCovid19 pneumonia, rule out lung involvement in high-risk cases, rapid triaging of sick patients when rapid antigen test is negative, to identify comorbid lung diseases and to detect complications. Various scoring systems have been developed to indicate the extent of lung involvement and severity of nCovid19 pneumonia. CT severity index is used to classify the disease as mild, moderate and severe. CT severity index is taken into consideration in the management of patients with nCovid19 pneumonia.
However, with our experience since last 1 year in treating more than 1000 patients with nCovid19, we feel many other factors in addition to the extent of lung involvement play a role in hypoxia and severity of illness in patients with nCovid19 pneumonia. Patients with preexisting compromised respiratory function due to any cause, heart disease and advanced age tend to develop more severe hypoxia than others. The most common causes for compromised respiratory function, we observed in our patients, were morbid obesity, obstructive airway disease, bronchiectasis, obstructive sleep apnea, preexisting parenchymal lung disease, pneumothorax, pleural effusion, pleural fibrosis, chest wall abnormalities, reduced level of consciousness and neurological deficit. Some patients had more than 1 contributing factor. In addition, superadded bacterial and fungal infections were observed in few patients after day 10 of the illness which lead to the worsening of hypoxia.
We have also observed some patients with mild CT severity progressing to develop severe hypoxia despite standard treatment, with no other contributing factors. CT was done in these patients during the early course of the disease, in the majority before day 7. nCovid19 pneumonia usually starts by day 5 after the initial symptoms and progresses till day 10 to day 15, sometimes even longer. Hence, the progression of the disease was probably the cause for worsening hypoxia in these patients.
On the contrary, some patients with CT showing moderate or severe disease had no or mild hypoxia, improved readily with treatment. We observed that these patients were in the early stage of pneumonia with only ground-glass opacity in the CT scan. Ground glass opacity is a rapidly reversible change, which responds readily to medications. In another group with mild hypoxia, where CT was done after day 10 of disease onset (they presented late) where the healing process would already have been started and further progression is less likely.
Secondary bacterial infection was the cause for worsening hypoxia in 5 patients after day 15. We also observed delayed progression after day 18 in two elderly patients. There was no obvious cause. Hence, we postulate this may be delayed progressing phenotype in elderly.
We have observed patients with predominant ground-glass opacities, organising pneumonia pattern, fibrosis had less severe degree of hypoxia than patients who had dense consolidation and crazy paving pattern. We have observed that in a given patient, lungs may show all patterns and morphology of involvement-Ground glass opacity/crazy paving/consolidation/organising pneumonia/fibrosis. The severity of hypoxia may depend on the degree and extent of the pattern and morphology of lung involvement.
We have observed increased incidence of barotrauma in nCovid19 pneumonia. Severity of barotrauma ranged from interstitial/mediastinal/surgical emphysema/pneumothorax in that order. We have observed spontaneous alveolar rupture leading to various degree of interstitial/mediastinal/surgical emphysema, pneumothorax even in patients without any positive pressure ventilation.
We also observed 4 patients with severe hypoxia who had moderate CT severity index with multiple pulmonary thromboembolism. Pulmonary vascular occlusion led to severe hypoxia in these patients and they had a poor outcome. We had 2 patients with cardiogenic pulmonary oedema with severe hypoxia, reported as high CT severity index. These patients made uneventful recovery with the treatment of the underlying heart disease and pulmonary oedema. We had 4 patients with chronic renal failure with volume overload pulmonary oedema, severe hypoxia, reported as high CT severity index. All these patients had uneventful recovery with treatment of the underlying renal disease and volume overload.
Hence, we conclude while reporting the CT in nCovid19 following factors should be taken into consideration
- Morphology of the lung lesion – Ground glass opacity/crazy paving/consolidation/organising pneumonia/fibrosis
- Extent of lung involved by each morphology
- Any evidence of pulmonary thromboembolism
- Any evidence of coexisting intrathoracic disease – pulmonary/pleural/chest wall/mediastinal disease which can contribute to hypoxia
- Any evidence of cardiogenic or fluid overload pulmonary oedema
- Any evidence of complications like-interstitial/mediastinal/surgical emphysema, pneumothorax
- Any features suggestive of secondary/superadded infection.
A clinician should assess the patient as a whole rather than just relying on CT severity index. We suggest a clinical scoring system should be adopted in the lines of pneumonia severity index where CT scan report should be taken as one of the parameters.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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