The nurse is percussing the lungs of a patient.
The nurse knows that percussion over normal adult lungs will reveal:

Step 1 is to determine the volume to administer. 4500 units ÷ (10,000 units/1 mL) = 0.45 mL. The nurse will administer 0.45 mL.

Choice A rationale

The bell of the stethoscope is designed to auscultate low-frequency sounds, such as certain heart murmurs or bowel sounds, due to its larger surface area and lower diaphragm tension. Breath sounds, however, are generally higher frequency and require the diaphragm for optimal clarity and discrimination of adventitious sounds, which are often subtle and require careful attention to pitch and quality.

Choice B rationale

Limiting auscultation to only the posterior chest misses significant lung fields, especially the anterior and lateral segments of the upper and middle lobes. Comprehensive respiratory assessment necessitates evaluating all accessible lung surfaces to detect localized abnormalities, ensuring no consolidation, atelectasis, or pleural effusions are overlooked, providing a complete diagnostic picture.

Choice C rationale

Instructing the patient to breathe in and hold their breath would prevent the continuous airflow necessary to generate breath sounds. Auscultation relies on the movement of air through the tracheobronchial tree. Holding the breath eliminates this vital acoustic phenomenon, rendering the assessment ineffective for evaluating air entry, presence of adventitious sounds, or symmetry.

Choice D rationale

Comparing sounds on the left and right sides allows for the identification of unilateral abnormalities, which are crucial for diagnosing localized pathologies. This systematic approach helps detect differences in breath intensity, the presence of unilateral adventitious sounds like wheezes or crackles, or diminished air entry, guiding further diagnostic investigation and treatment.