Why assess sputum?

Well if the sputum was relatively clear and then goes all Technicolor, that could indicate an infection. (If you're caring for a vented or trached pt, you WILL see sputum, whether the pt has pneumonia or not).

You want to assess consistency; the thicker it is, the harder it is to clear. I've seen people respiratory arrest from mucus plugs -- if you notice sputum becoming increasingly thick, you can intervene before it becomes an emergency.

Pink, frothy sputum indicates pulmonary edema.

Certain bugs such as pseudomonas have a distinct odor.

As what was mentioned, sputum is significant when it comes to assessments because having purulent/changes in colors indicates infection. Mucoid may be viral bronchitis, pink/colorless tinged mucoid = lung tumor?, froth pink may be PEdema, bloody may be a PEmboli?, foul smelling could be a lung abscess, etc.

But it's not just color you're assessing for;

For coughing, you'd be seeing if it is a dry/productive cough, onset, severity, wheezing, duration, pattern, symptoms, prescriptions?, etc.

For the sputum, you'd be checking the amount, presence of hemoptysis, smell, consistency, etc.