Considering that PPHN is a syndrome secondary to increased
pulmonary vascular resistance, to the point of inducing
right-left shunt, its physiopathology is related to the major
factors that lead to these alterations during the perinatal
period. The following classification illustrates the
different categories of diseases associated with increased
pulmonary vascular resistance. A disease classified in one
category often has manifestations characteristics of another
form. Fig. 5 illustrates some of the forms described
below