In a patient with a pneumothorax, unilateral chest expansion means:

• A. both lungs are expanding when he inhales
• B. both sides of the chest are moving minimally
• C. only one side of the chest rises when he inhales
• D. chest and abdomen are moving in opposite directions

Answer: (C)

In a patient with a pneumothorax, unilateral chest expansion indicates that only one side of the chest is rising during inhalation. This occurs because the presence of air in the pleural space disrupts the normal negative pressure that helps keep the lung inflated on that side. As a result, while the unaffected lung is able to expand normally, the lung on the affected side cannot expand properly due to the air in the pleural cavity, leading to the noticeable difference in chest movement.

This phenomenon is a key clinical sign in assessing patients with respiratory distress or chest trauma, as it can help healthcare providers identify the presence of a pneumothorax. Monitoring for unilateral expansion is crucial because it may indicate compromised respiratory function and the need for urgent intervention.