What type of sputum color might suggest the presence of old blood?

Brown sputum is indicative of the presence of old blood, usually due to the oxidation of hemoglobin. When blood is mixed with sputum, it can undergo changes over time, leading to a brown coloration. This can occur in chronic conditions or when there is bleeding that has been resolved, allowing for the integration of the oxidized blood with the mucus in the airways.

In contrast, yellow sputum typically suggests a bacterial infection or inflammation, as it is associated with an increased presence of white blood cells. Mucoid sputum is generally clear or white and suggests chronic bronchitis or other non-infectious conditions. Green sputum is often linked to infections, particularly those caused by pseudomonas or other bacterial pathogens, indicating acute inflammation rather than old blood. Thus, brown sputum serves as a distinct sign that points toward the presence of old blood in the respiratory system.