Complex sentence: Bronchospasm, a life-threatening situation, occurs when the smooth muscular tissue of the bronchioles constricts, severely narrowing their diameter, the most common cause of this is asthma.
Split into simpler sentences: Bronchospasm, a potentially life-threatening situation, occurs when the smooth muscular tissue of the bronchioles constricts, severely narrowing their diameter. The most common cause of this is asthma.