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.
A few words are in order regarding the Sale of Indulgences that Martin Luther so much decried. The clergy were authorized by the Catholic Church to absolve penitents from the guilt of his sins and from punishment in the hellish inferno of the hereafter, but it did not absolve them from doing penance on earth.