How might breath-holding lead to complications during ascent?

Breath-holding during ascent can lead to barotrauma due to the changes in atmospheric pressure as altitude increases. When a person holds their breath, the air within the lungs cannot be expelled. As the aircraft ascends, the external pressure decreases, but the pressure of the trapped air inside the lungs remains higher relative to the surrounding environment. This pressure differential can cause the alveoli, or small air sacs in the lungs, to expand and potentially rupture, leading to barotrauma. This might result in serious complications such as pneumothorax and mediastinal emphysema.

The other options do not accurately reflect the physiological consequences of breath-holding during ascent. Increased lung capacity is unrelated as breath-holding actually restricts airflow. Holding one’s breath does not inherently lead to a decrease in blood pressure but may actually cause an increase in pressure due to stress and potential hypoxia. Lastly, breath-holding does not improve oxygenation; rather, it can lead to decreased oxygen levels in the blood and hypoxia as oxygen supply diminishes without inhalation.