Dyspnea is usually caused by disorders of the lungs or heart (see Table: Some Causes and Features of Shortness of Breath). Pulmonary embolism (sudden blockage of an artery of the lung, usually by a blood clot) is a less common, but serious cause. However, such people may also develop another disorder.
A plenary indulgence means that by the merits of Jesus Christ, the Blessed Virgin Mary and all the saints, the full remission of the temporal punishment due to sacramentally forgiven sins is obtained. The person becomes as if just baptized and would fly immediately to heaven if he died in that instant.
What an Indulgence does is to take an occasion of such expiation (a certain prayer, penance, charity or other designated work) and add to its intrinsic merit before God an additional value based on the treasury of merits of Jesus Christ, and those perfectly united to Him in heaven (the saints).