1. What lung volume is pulmonary vascular resistance at its lowest?
2. Which of the following is not a way to treat a pulmonary hypertensive crisis?
a) Oxygen supplementation
3. In a child without congenital heart disease, what are the signs of a pulmonary hypertensive crisis?
a) Cardiovascular collapse
d) Increased EtCO2
ANSWERS & EXPLANATIONS
1. D. Due to the relative contributions of septal and corner vessels, pulmonary vascular resistance is "U" shaped, with maximal PVR at RV and TLC and the nadir at FRC.
2. D. While sildenafil, a PDE5 inhibitor, is used to treat pulmonary hypertension in children, it is not used to treat acute episodes of pulmonary hypertension. All of the other choices can be helpful in managing a pulmonary hypertensive crisis.
3. A Without a "pop-off" such as a PFO or a VSD, then increased PVR will lead to cardiovascular collapse as there will be insufficient pulmonary blood flow and thus insufficient LV preload. In order to have hypoxemia, you would either have to have an intracardiac lesion to shunt R to L or increasing intrapulmonary shunt. ETCO2 decreases, not increases, with pulmonary hypertension as the dead space fraction increases.