Which finding would most likely indicate the presence of a respiratory infection in a client with asthma?

The presence of a cough that is productive of yellow sputum is significant in indicating a respiratory infection, particularly in a client with asthma. Yellow sputum often suggests the presence of an infectious process, as it typically contains neutrophils and other immune cells responding to an infection, often due to bacteria. In the context of asthma, this finding could suggest that a respiratory infection is exacerbating the asthmatic condition, which is crucial for both diagnosis and management.

While bilateral expiratory wheezing can indicate an asthma exacerbation, it is not specific to respiratory infections. Similarly, chest tightness can be a common symptom in asthma but does not necessarily point toward an infection. An elevated respiratory rate, such as 30 breaths per minute, can indicate increased work of breathing or distress, which may occur in various conditions, including infections, but does not provide the specificity that yellow sputum does in predicting the presence of a respiratory infection.