Patients with acute severe asthma requiring mechanical ventilation are difficult to manage because of which of the following?

• A. Uneven alveolar hyperexpansion
• B. Uniform alveolar hyperexpansion
• C. Increased central venous pressure
• D. Excellent airway clearance

Answer: (A)

The main idea is that in severe asthma the ventilation pattern becomes highly uneven due to widespread airway narrowing. Some airways are vastly more constricted than others, so air gets trapped in some regions while others ventilate less effectively. This leads to patchy or uneven hyperinflation of alveoli rather than a uniform expansion across the lung. That heterogeneity makes mechanical ventilation tricky: you can get dynamic hyperinflation and auto-PEEP, higher and unpredictable pressures, and difficulty delivering a stable tidal volume without risking barotrauma or hemodynamic compromise.

Uniform alveolar hyperexpansion isn’t correct because the obstruction isn’t the same everywhere, so inflation isn’t equal. Increased central venous pressure isn’t the defining difficulty here, since the key problem is the uneven ventilation and air trapping. Excellent airway clearance isn’t typical in this setting; bronchospasm and mucus plugging tend to hinder clearance rather than improve it.