What is one symptom of respiratory distress?

Cyanosis is a key symptom of respiratory distress. It occurs when there is a lack of sufficient oxygen in the bloodstream, causing the skin, particularly around the lips, fingertips, and other extremities, to take on a bluish or grayish color. This discoloration is a clear indicator that the body is not receiving enough oxygen, which is a critical condition that can arise from various respiratory problems like asthma, pneumonia, or chronic obstructive pulmonary disease (COPD).

In contrast, the other options do not indicate respiratory distress. Sudden strength might imply an increase in physical capability, which is not associated with trouble breathing. Increased appetite generally suggests well-being and does not correlate with respiratory issues. A calm demeanor can often be seen in individuals who are not in distress, as anxiety or panic typically accompanies respiratory distress, causing symptoms like confusion or agitation. Thus, cyanosis stands out as the most relevant symptom indicative of respiratory distress.