Oxygen Therapy: Devices, Targets & Risks

Answer: B. Lung abscess results from aspiration of oropharyngeal contents containing anaerobic bacteria into dependent lung segments (right lower lobe, posterior segments, or left upper lobe segments). Risk factors for aspiration include impaired swallowing (altered consciousness, dysphagia, neurologic disease), recent anesthesia, and COPD. Aspirated anaerobes (Peptostreptococcus, Prevotella, Bacteroides, Fusobacterium, anaerobic streptococci) are normally suppressed by aerobic oropharyngeal flora, but in the low-oxygen environment of consolidated lung tissue, anaerobes proliferate and cause a necrotizing infection. Progressive inflammation and necrosis enlarge the infected focus until it erodes into a bronchus, creating a communication between the abscess cavity and the airway. This bronchial communication allows air to enter the cavity (creating the characteristic air-fluid level on radiography, where air above is separated from necrotic fluid/pus below by a horizontal level) and facilitates drainage of pus, reducing pleural involvement. Histologically, the abscess shows central purulent necrosis surrounded by granulation tissue and chronic inflammation representing the host's containment response. The foul-smelling sputum results from anaerobic bacterial metabolism producing volatile organic acids. Option A incorrectly implies sterile initial necrosis; option C invokes septic embolism without aspiration risk; options D and E incorrectly attribute abscess to fungal superinfection or bullae rupture.

Answer: D. In COPD, excessive oxygen can blunt the respiratory drive and raise carbon dioxide, so the nurse titrates the oxygen down to keep the client within the ordered target range and reassesses (option D). Increasing the flow to maximize saturation (A) risks carbon dioxide retention. Removing the oxygen entirely (B) could cause hypoxemia and overcorrects the problem. Leaving it unchanged on the belief that higher is always better (C) ignores the specific target. Titrating to the ordered range balances adequate oxygenation against the risk of retention. The nurse monitors the respiratory rate, level of consciousness, and saturation after adjusting.

Answer: A. In an acute exacerbation of chronic obstructive pulmonary disease, excessive oxygen can worsen carbon dioxide retention and acidosis in susceptible clients, so oxygen is titrated to a target saturation range (option A). Routine high-flow oxygen aimed at a saturation of 100% (B) is associated with worse outcomes in this population. Withholding oxygen until a blood gas is available (C) leaves a hypoxic client untreated, and hypoxia is the more immediate threat. Waiting for visible cyanosis (D) is unreliable because it is a very late sign. The nurse monitors the saturation, work of breathing, and level of consciousness closely.