No abstract

Performing a 6MWT is feasible and practical in young children. This study provides data on normal children against which the performance of sick children and the response to therapeutic intervention can be judged.

New pulmonary hypertension-specific medicines have improved survival in children as in adults. Outcome in this series compares favourably with international outcome data.

We showed, for the first time, that the incidence of IPAH is lower in children than adults and that the clinical features can be different. Most children present with clinical evidence of advanced disease and clinical status at presentation is predictive of outcome. This 7-year experience confirms the significant improvement in survival over historical controls.

In the adult lung the pulmonary arteries run alongside the airways and the pulmonary veins show a similar branching pattern to the arteries, though separated from them. During early fetal development the airways act as a template for pulmonary blood vessel development in that the vessels form by vasculogenesis around the branching airways. In later lung development the capillary bed is essential for alveolar formation. This paper reviews evidence for the interaction of the airways and blood vessels in both normal and abnormal lung development.

From a case of congenital diaphragmatic hernia the pattern of growth of the airways, alveoli, and pulmonary arteries of both lungs, each hypoplastic, has been analysed quantitatively. The impairment of growth for each type of structure is not necessarily the same and differs in each lung. Airway and alveolar numbers are both greatly reduced, although the latter are more nearly normal when related to the number of terminal bronchioli in the lung. In each lung the size of the pulmonary artery at the hilum is appropriate to the lung volume but small for the age of the child. Muscle is found in much smaller arteries than is normal but not to a more peripheral level. The way the lungs in a case of congenital diaphragmatic hernia might grow after surgical correction of the hernia is discussed and a plea made for respiratory physiological studies in such cases.

No abstract

Recent studies on the morphogenesis of the pulmonary arteries have focused on nonhuman species such as the chick and the mouse. Using immunohistochemical techniques, we have studied 16 lungs from human embryos and fetuses from 28 d of gestation to newborn, using serial sections stained with a panel of antibodies specific for endothelium, smooth muscle, and extracellular matrix proteins. Cell replication was also assessed. Serial reconstruction showed a continuity of circulation between the heart and the capillary plexus from at least 38 d of gestation. The intrapulmonary arteries appeared to be derived from a continuous expansion of the primary capillary plexus that is from within the mesenchyme, by vasculogenesis. The arteries formed by continuous coalescence of endothelial tubes alongside the newly formed airway. Findings were consistent with the pulmonary arterial smooth muscle cells being derived from three sites in a temporally distinct sequence: the earliest from the bronchial smooth muscle, later from the mesenchyme surrounding the arteries, and last from the endothelial cells. Despite their different origins, all smooth muscle cells followed the same sequence of expression of smooth muscle-specific cytoskeletal proteins with increasing age. The order of appearance of these maturing proteins was from the subendothelial cells outward across the vessel wall and from hilum to periphery. The airways would seem to act as a template for pulmonary artery development. This study provides a framework for studying the signaling mechanisms controlling the various aspects of lung development.