The differential diagnosis of CPO is shown in Table 1.
| Sign | CPO | COPD | Pneumonia | PE |
| Heart rate | ||||
| Blood pressure | ||||
| Temperature | ||||
| O2 saturations | ||||
| Chest signs | Bilateral crepitations | Diffuse wheeze | Focal crepitations | Clear |
| Skin | Cold, pale and clammy | Dry and warm | Flushed and warm | Dry |
| Heart sounds | Murmurs, 3rd/4th heart sounds | Normal | Normal | Normal |