These are six major causes for dyspnea. Pulmonary bronchial constriction prevents the passage of air into the lungs which contributes to dyspnea. (Possible) foreign bodies can become trapped or logged within the trachea restricting air flow. Pulmonary embolisms can prevent complete oxygenation of the blood in the alveoli due to restricted blood flow. Pneumothorax collapses the lung and prevents full expansion, restricting oxygenation. Pump failure refers to the heart not beating appropriately. If the heart is not perfusing the lungs than the lungs will be unable to oxygenate the blood. Pneumonia leads to poor lung ventilation as well.