administration of Oxygen (HLHS); neonates with severe PPHN may not show
improvement in saturation with oxygen. In addition, increased pulmonary interstitial
markings in TAPVR can be mistaken for RDS or transient tachypnea, particularly in late
preterm infants. Echocardiography is needed to make a more accurate diagnosis in
neonates with hypoxic respiratory failure and PPHN.
DIAGNOSIS:
- X-ray chest: may be normal or show “black out” lung fields or haziness/patchy
infiltrates from parenchymal lung disease (meconium, pneumonia or RDS) - ABG: In the presence of right to left shunting via PDA, pre ductal PaO2(right
radial artery) is higher ( 10-15 mm of Hg) than post ductal PaO2(umbilical artery, left
radial artery, or posterior tibial artery). However, 2-site sampling for arterial blood is
invasive and is not recommended for diagnosis. - Oxygen saturation: A difference of >5% between pre ductal and post ductal
oxygen saturations is considered indicative of right to left ductal shunt seen in PPHN.
However, this difference is also seen in CHD with right to left shunts. Monitoring pre-
and post-ductal saturations is useful in gauging the response to pulmonary vasodilator
therapy. Neonates with TGA may have higher postductal than preductal saturation. - Echocardiogram: Helpful to distinguish cyanotic congenital heart disease from
PPHN. ECHO also documents the presence of right-to-left or bidirectional shunts at the
level of the PDA or PFO and estimate the pulmonary artery pressure from Doppler
velocity measurement of the tricuspid regurgitation jet. Echo can also allow assess the
progression of PPHN over time.