Hemoptysis is defined as the expectoration of blood or the presence of blood in the sputum. Young children usually swallow their sputum; as a result, hemoptysis is rare in children unless the bleeding is substantial [1,2]. The age of presentation is bimodal, with a frequency peaks in children less than five years of age and in adolescents 11 years or older .
In adults, the severity of hemoptysis is classified based upon the estimated volume of blood expectorated. In pediatric patients with hemoptysis, no such classification correlating severity with blood loss exists. Thus, clinical judgment is the primary tool that clinicians have in assessing the severity of hemoptysis in children .
The lung contains two separate blood supplies:
- The pulmonary arterial circulation is a high volume, low pressure system in which maximal pressures normally do not exceed 40 mmHg . Its branches accompany the bronchi down to the level of the terminal bronchioles. Ultimately, pulmonary vessels branch to supply the capillary bed in the walls of the alveoli and then return to the left atrium via the pulmonary veins.
- The bronchial circulation carries a much smaller volume of oxygenated blood, but does so at higher, systemic pressures. Usually, the patient has three recognizable bronchial arteries, two that supply the left lung and one that supplies the right, although 20 to 30 percent of individuals have two vessels on each side . These arteries typically originate from the aorta or the intercostal arteries and perfuse conductive airways approximately to the level of the terminal bronchioles.
Bleeding can arise from either system. Although bleeding usually is minimal when it arises from the pulmonary circulation (eg, in the presence of left sided cardiac disease), it can be substantial when it arises from the bronchial circulation because of the higher hydrostatic pressures promoting hemorrhage.