Final answer:
Chesty coughs, characterized by thick mucus, should not be suppressed because coughing helps the body expel mucus from the airways.
Step-by-step explanation:
When a patient has a chesty cough with thick mucus, doctors generally advise against suppressing the cough. The reason for this is that the cough is considered 'productive,' meaning it helps the body expel the mucus from the airways. Suppressing the cough with cough suppressants can hinder the body's natural process of clearing the mucus, leading to the mucus remaining in the airways and potentially causing further congestion and discomfort.