Final answer:
For auscultation of the posterior lung fields in a client with pneumonia, the PN should position the client sitting up or leaning forward. Listening with a stethoscope reveals abnormal breath sounds, supporting the diagnosis alongside other clinical indicators and chest radiograph findings.
Step-by-step explanation:
To auscultate the posterior lung fields of a client diagnosed with left lower lobe pneumonia, the Practical Nurse (PN) should position the client to allow for the best possible access to the lung area of interest. Typically, this would involve having the client sit up straight or lean slightly forward, which makes the lungs more accessible for examination. Placing the stethoscope directly on the patient's back, the PN can listen for abnormal breath sounds, such as the crepitation or crackling sounds indicative of pneumonia. The presence of these sounds, along with other clinical findings such as hypoxemia, elevated heart rate, and a chest radiograph showing shadows or consolidation, would support the diagnosis of pneumonia.