Respiratory Practice Questions

Correct Answer: A) Respiratory acidosis with metabolic compensation

Rationale: With pH 7.32 (acidotic), PaCO2 58 (elevated—respiratory problem), and HCO3- 28 (elevated—metabolic compensation), this is respiratory acidosis. In COPD exacerbations, poor ventilation traps CO2, causing respiratory acidosis. The elevated HCO3- represents kidney retention of bicarbonate attempting to normalize pH—this is metabolic compensation. The low PaO2 is also concerning and requires oxygen therapy.

Key Concept: Always check pH first to determine acidosis vs. alkalosis, then look at the primary problem (PaCO2 or HCO3-). The system trying to compensate will be abnormal in the opposite direction.

Correct Answer: B) Combined beta-2 agonist (albuterol) and anticholinergic (ipratropium) provide enhanced bronchodilation

Rationale: Albuterol (beta-2 agonist) activates beta receptors on airways causing bronchodilation. Ipratropium blocks acetylcholine receptors, preventing bronchoconstriction. Using both mechanisms together provides synergistic bronchodilation through different pathways. This combination is especially useful in acute exacerbations where maximum bronchodilation is needed quickly.

Key Concept: Combination therapy using different drug classes often provides better outcomes by targeting multiple pathways. In asthma: beta-agonists + anticholinergics for acute symptoms, and adding inhaled corticosteroids for inflammation control.

Correct Answer: B) Streptococcus pneumoniae

Rationale: While S. pneumoniae is the most common cause of CAP overall, elderly and immunocompromised patients also have higher risk for Gram-negative organisms like P. aeruginosa and Legionella, as well as atypical organisms. However, S. pneumoniae remains the most frequent cause across populations. The question context (nursing home patient) doesn't indicate healthcare-associated pneumonia or severe risk factors that would shift the most likely pathogen.

Key Concept: Common CAP pathogens: S. pneumoniae (most common), H. influenzae, M. pneumoniae, C. pneumoniae. Risk factors (age, immunosuppression, mechanical ventilation) influence pathogen likelihood. Always consider healthcare-associated pneumonia (HAP) if hospitalized >48 hours or recent healthcare exposure.

Correct Answer: B) Assess for treatable causes (hypoxia, hypercarbia, tube obstruction, pain)

Rationale: When a patient is fighting the ventilator ("patient-ventilator dyssynchrony"), a systematic assessment is essential before intervening. Common causes include: inadequate oxygenation, CO2 retention, endotracheal tube obstruction, secretions, pain, anxiety, or inadequate sedation. Addressing the underlying cause is more effective than just sedating. Check ABG, lung sounds, chest X-ray, and comfort level first.

Key Concept: Ventilator management requires systematic troubleshooting. "Patient-ventilator asynchrony" has specific causes—identify and treat the cause, not just the symptom. Over-sedation is harmful and delays weaning.

Correct Answer: B) Moderate ARDS (P/F ratio 101-200)

Rationale: The PaO2/FiO2 (P/F) ratio is used to classify ARDS severity according to Berlin criteria: Mild (201-300), Moderate (101-200), Severe (≤100). A P/F ratio of 150 indicates moderate ARDS with significant oxygenation impairment. This patient requires high levels of PEEP and FiO2 to maintain oxygenation, along with management of the underlying cause of ARDS.

Key Concept: The P/F ratio allows objective assessment of oxygenation dysfunction severity independent of ventilator settings. Severe ARDS indicates very poor prognosis and may warrant consideration of advanced therapies like prone positioning or extracorporeal membrane oxygenation (ECMO).